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Is Sugar Really Toxic? Sifting through the Evidence

The views expressed are those of the author and are not necessarily those of Scientific American.

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Credit: Lauri Andler (Phantom), via Wikimedia Commons

Our very first experience of exceptional sweetness—a dollop of buttercream frosting on a parent’s finger; a spoonful of strawberry ice cream instead of the usual puréed carrots—is a gustatory revelation that generally slips into the lacuna of early childhood. Sometimes, however, the moment of original sweetness is preserved. A YouTube video from February 2011 begins with baby Olivia staring at the camera, her face fixed in rapture and a trickle of vanilla ice cream on her cheek. When her brother Daniel brings the ice cream cone near her once more, she flaps her arms and arches her whole body to reach it.

Considering that our cells depend on sugar for energy, it makes sense that we evolved an innate love for sweetness. How much sugar we consume, however—as well as how it enters the body and where we get it from in the first place—has changed dramatically over time. Before agriculture, our ancestors presumably did not have much control over the sugars in their diet, which must have come from whatever plants and animals were available in a given place and season. Around 6,000 BC, people in New Guinea began to grow sugarcane, chewing and sucking on the stalks to drink the sweet juice within. Sugarcane cultivation spread to India, where by 500 BC people had learned to turn bowls of the tropical grass’s juice into crude crystals. From there sugar traveled with migrants and monks to China, Persia, northern Africa and eventually to Europe in the 11th century.

For more than 400 years, sugar remained a luxury in Europe—an exotic spice—until manufacturing became efficient enough to make “white gold” much more affordable. Christopher Columbus brought sugarcane to the New World in 1493 and in the 16th and 17th centuries European powers established sugarcane plantations in the West Indies and South America. Sugar consumption in England increased by 1,500 percent between the 18th and 19th centuries. By the mid 19th century, Europeans and Americans had come to regard refined sugar as a necessity. Today, we add sugar in one form or another to the majority of processed foods we eat—everything from bread, cereals, crunchy snacks and desserts to soft drinks, juices, salad dressings and sauces—and we are not too stingy about using it to sweeten many raw and whole foods as well.

By consuming so much sugar we are not just demonstrating weak willpower and indulging our sweet tooth—we are in fact poisoning ourselves according to a group of doctors, nutritionists and biologists, one of the most prominent members of which is Robert Lustig of the University of California, San Francisco, famous for his viral YouTube video “Sugar: The Bitter Truth.” A few journalists, such as Gary Taubes and Mark Bittman, have reached similar conclusions. Sugar, they argue, poses far greater dangers than cavities and love handles; it is a toxin that harms our organs and disrupts the body’s usual hormonal cycles. Excessive consumption of sugar, they say, is one of the primary causes of the obesity epidemic and metabolic disorders like diabetes, as well as a culprit of cardiovascular disease. More than one-third of American adults and approximately 12.5 million children and adolescents in the U.S. are obese. In 1980, 5.6 million Americans were diagnosed with diabetes; in 2011 more than 20 million Americans had the illness.

Credit: Romain Behar, via Wikimedia Commons

The argument that sugar is a toxin depends on some technical details about the different ways the human body gets energy from different types of sugar. Today, Americans eat most of their sugar in two main forms: table sugar and high-fructose corn syrup. A molecule of table sugar, or sucrose, is a bond between one glucose molecule and one fructose molecule—two simple sugars with the same chemical formula, but slightly different atomic structures. In the 1960s, new technology allowed the U.S. corn industry to cheaply convert corn-derived glucose intro fructose and produce high fructose corn syrup, which—despite its name—is almost equal parts free-floating fructose and glucose: 55 percent fructose, 42 percent glucose and three percent other sugars. Because fructose is about twice as sweet as glucose, an inexpensive syrup mixing the two was an appealing alternative to sucrose from sugarcane and beets.

Regardless of where the sugar we eat comes from, our cells are interested in dealing with fructose and glucose, not the bulkier sucrose. Enzymes in the intestine split sucrose into fructose and glucose within seconds, so as far as the human body is concerned sucrose and high-fructose corn syrup are equivalent. The same is not true for their constituent molecules. Glucose travels through the bloodstream to all of our tissues, because every cell readily converts glucose into energy. In contrast, liver cells are one of the few types of cells that can convert fructose to energy, which puts the onus of metabolizing fructose almost entirely on one organ. The liver accomplishes this primarily by turning fructose into glucose and lactate. Eating exceptionally large amounts of fructose taxes the liver: it spends so much energy turning fructose into other molecules that it may not have much energy left for all its other functions. A consequence of this energy depletion is production of uric acid, which research has linked to gout, kidney stones and high blood pressure.

The human body strictly regulates the amount of glucose in the blood. Glucose stimulates the pancreas to secrete the hormone insulin, which helps remove excess glucose from blood, and bolsters production of the hormone leptin, which suppresses hunger. Fructose does not trigger insulin production and appears to raise levels of the hormone grehlin, which keeps us hungry. Some researchers have suggested that large amounts of fructose encourage people to eat more than they need. In studies with animals and people by Kimber Stanhope of the University of California Davis and other researchers, excess fructose consumption has increased fat production, especially in the liver, and raised levels of circulating triglycerides, which are a risk factor for clogged arteries and cardiovascular disease. Some research has linked a fatty liver to insulin resistance—a condition in which cells become far less responsive to insulin than usual, exhausting the pancreas until it loses the ability to properly regulate blood glucose levels. Richard Johnson of the University of Colorado Denver has proposed that uric acid produced by fructose metabolism also promotes insulin resistance. In turn insulin resistance is thought to be a major contributor to obesity and Type 2 diabetes; the three disorders often occur together.

Because fructose metabolism seems to kick off a chain reaction of potentially harmful chemical changes inside the body, Lustig, Taubes and others have singled out fructose as the rotten apple of the sugar family. When they talk about sugar as a toxin, they mean fructose specifically. In the last few years, however, prominent biochemists and nutrition experts have challenged the idea that fructose is a threat to our health and have argued that replacing fructose with glucose or other sugars would solve nothing. First, as fructose expert John White points out, fructose consumption has been declining for more than a decade, but rates of obesity continued to rise during the same period. Of course, coinciding trends alone do not definitively demonstrate anything. A more compelling criticism is that concern about fructose is based primarily on studies in which rodents and people consumed huge amounts of the molecule—up to 300 grams of fructose each day, which is nearly equivalent to the total sugar in eight cans of Coke—or a diet in which the vast majority of sugars were pure fructose. The reality is that most people consume far less fructose than used in such studies and rarely eat fructose without glucose.

Credit: Thamizhpparithi Maari, Wikimedia Commons

On average, people in America and Europe eat between 100 and 150 grams of sugar each day, about half of which is fructose. It’s difficult to find a regional diet or individual food that contains only glucose or only fructose. Virtually all plants have glucose, fructose and sucrose—not just one or another of these sugars. Although some fruits, such as apples and pears, have three times as much fructose as glucose, most of the fruits and veggies we eat are more balanced. Pineapples, blueberries, peaches, carrots, corn and cabbage, for example, all have about a 1:1 ratio of the two sugars. In his New York Times Magazine article, Taubes claims that “fructose…is what distinguishes sugar from other carbohydrate-rich foods like bread or potatoes that break down upon digestion to glucose alone.” This is not really true. Although potatoes and white bread are full of starch—long chains of glucose molecules—they also have fructose and sucrose. Similarly, Lustig has claimed that the Japanese diet promotes weight loss because it is fructose-free, but the Japanese consume plenty of sugar—about 83 grams a day on average—including fructose in fruit, sweetened beverages and the country’s many meticulously crafted confectioneries. High-fructose corn syrup was developed and patented in part by Japanese researcher Yoshiyuki Takasaki in the 1960s and ’70s.

Not only do many worrying fructose studies use unrealistic doses of the sugar unaccompanied by glucose, it also turns out that the rodents researchers have studied metabolize fructose in a very different way than people do—far more different than originally anticipated. Studies that have traced fructose’s fantastic voyage through the human body suggest that the liver converts as much as 50 percent of fructose into glucose, around 30 percent of fructose into lactate and less than one percent into fats. In contrast, mice and rats turn more than 50 percent of fructose into fats, so experiments with these animals would exaggerate the significance of fructose’s proposed detriments for humans, especially clogged arteries, fatty livers and insulin resistance.

In a series of meta-analyses examining dozens of human studies, John Sievenpiper of St. Michael’s Hospital in Toronto and his colleagues found no harmful effects of typical fructose consumption on body weight, blood pressure or uric acid production. In a 2011 study, Sam Sun—a nutrition scientist at Archer Daniels Midland, a major food processing corporation—and his colleagues analyzed data about sugar consumption collected from more than 25,000 Americans between 1999 and 2006. Their analysis confirmed that people almost never eat fructose by itself and that for more than 97 percent of people fructose contributes less daily energy than other sugars. They did not find any positive associations between fructose consumption and levels of trigylcerides, cholesterol or uric acid, nor any significant link to waist circumference or body mass index (BMI). And in a recent BMC Biology Q&A, renowned sugar expert Luc Tappy of the University of Lausanne writes: “Given the substantial consumption of fructose in our diet, mainly from sweetened beverages, sweet snacks, and cereal products with added sugar, and the fact that fructose is an entirely dispensable nutrient, it appears sound to limit consumption of sugar as part of any weight loss program and in individuals at high risk of developing metabolic diseases. There is no evidence, however, that fructose is the sole, or even the main factor in the development of these diseases, nor that it is deleterious to everybody.”

To properly understand fructose metabolism, we must also consider in what form we consume the sugar, as explained in a recent paper by David Ludwig, Director of the New Balance Foundation Obesity Prevention Center of Boston Children’s Hospital and a professor at Harvard. Drinking a soda or binging on ice cream floods our intestines and liver with large amounts of loose fructose. In contrast, the fructose in an apple does not reach the liver all at once. All the fiber in the fruit—such as cellulose that only our gut bacteria can break down—considerably slows digestion. Our enzymes must first tear apart the apple’s cells to reach the sugars sequestered within. “It’s not just about the fiber in food, but also its very structure,” Ludwig says. “You could add Metamucil to Coca Cola and not get any benefit.” In a small but intriguing study, 17 adults in South Africa ate primarily fruit—about 20 servings with approximately 200 grams of total fructose each day—for 24 weeks and did not gain weight, develop high blood pressure or imbalance their insulin and lipid levels.

To strengthen his argument, Ludwig turns to the glycemic index, a measure of how quickly food raises levels of glucose in the blood. Pure glucose and starchy foods such as Taubes’s example of the potato have a high glycemix index; fructose has a very low one. If fructose is uniquely responsible for obesity and diabetes and glucose is benign, then high glycemic index diets should not be associated with metabolic disorders—yet they are. A small percentage of the world population may in fact consume so much fructose that they endanger their health because of the difficulties the body encounters in converting the molecule to energy. But the available evidence to date suggests that, for most people, typical amounts of dietary fructose are not toxic.

Credit: Jan Homann, Wikimedia Commons

Even if Lustig is wrong to call fructose poisonous and saddle it with all the blame for obesity and diabetes, his most fundamental directive is sound: eat less sugar. Why? Because super sugary, energy-dense foods with little nutritional value are one of the main ways we consume more calories than we need, albeit not the only way. It might be hard to swallow, but the fact is that many of our favorite desserts, snacks, cereals and especially our beloved sweet beverages inundate the body with far more sugar than it can efficiently metabolize. Milkshakes, smoothies, sodas, energy drinks and even unsweetened fruit juices all contain large amounts of free-floating sugars instantly absorbed by our digestive system.

Avoiding sugar is not a panacea, though. A healthy diet is about so much more than refusing that second sugar cube and keeping the cookies out of reach or hidden in the cupboard. What about all the excess fat in our diet, so much of which is paired with sugar and contributes to heart disease? What about bad cholesterol and salt? “If someone is gaining weight, they should look to sugars as a place to cut back,” says Sievenpiper, “but there’s a misguided belief that if we just go after sugars we will fix obesity—obesity is more complex than that. Clinically, there are some people who come in drinking way too much soda and sweet beverages, but most people are just overconsuming in general.” Then there’s all the stuff we really should eat more of: whole grains; fruits and veggies; fish; lean protein. But wait, we can’t stop there: a balanced diet is only one component of a healthy lifestyle. We need to exercise too—to get our hearts pumping, strengthen our muscles and bones and maintain flexibility. Exercising, favoring whole foods over processed ones and eating less overall sounds too obvious, too simplistic, but it is actually a far more nuanced approach to good health than vilifying a single molecule in our diet—an approach that fits the data. Americans have continued to consume more and more total calories each year—average daily intake increased by 530 calories between 1970 and 2000—while simultaneously becoming less and less physically active. Here’s the true bitter truth: Yes, most of us should make an effort to eat less sugar—but if we are really committed to staying healthy, we’ll have to do a lot more than that.

About the Author: Ferris Jabr is an associate editor focusing on neuroscience and psychology. Follow on Twitter @ferrisjabr.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. jtdwyer 9:15 am 07/15/2013

    Well done article – really sweet!

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  2. 2. hanmeng 10:51 am 07/15/2013

    Super blog post. And yet while some Scientific American pieces are little more than regurgitations of news releases, this balanced consideration is dismissed with the standard caveat “The views expressed are those of the author and are not necessarily those of Scientific American.” It’s a shame.

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  3. 3. nicholasjh1 11:35 am 07/15/2013

    @jtdwyer LOL

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  4. 4. drafter 11:38 am 07/15/2013

    it’s like everything else, something they used to teach, moderation in all things.

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  5. 5. Bill_Crofut 2:27 pm 07/15/2013

    Re: “Considering that our cells depend on sugar for energy, it makes sense that we evolved an innate love for sweetness.”

    How did our cells survive while the sweet tooth was “evolving?”

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  6. 6. Bill_Lagakos 2:47 pm 07/15/2013

    To further complicate things, the impact of fructose on health will differ depending on the metabolic and hormonal milieu. That is, I would expect excess fructose to be worse for someone who is weight stable or gaining weight than in someone who is losing weight.

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  7. 7. LDMAYA 2:58 pm 07/15/2013

    The article is based on wrong premises:
    1. “Lustig, Taubes and others have singled out fructose as the rotten apple of the sugar family. When they talk about sugar as a toxin, they mean fructose specifically.”
    2. “Lustig [calls] fructose poisonous and saddle it with all the blame for obesity and diabetes”

    The studies by Lustig I have seen talk about:
    a. Large doses of sugars taken over time are toxic, mainly to the liver but also to the pancreas.
    b. The doses of the large majority of processed food are at toxic levels. Furthermore, the average dosage has increased drastically in the last few decades.
    c. Fructose is highlighted because its name fools most into thinking it is less harmful, but given the low levels of fiber (structural or not) in processed foods it is even more dangerous than the other usual sugars given it high .

    I have not see Dr. Lustig blame, ask to regulate, or ban fructose as the author of this blog, Ferris Jabr, states. Maybe I have been reading different papers?
    If so, a link to this author’s sources would be welcomed.

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  8. 8. thenorthcountrywoman 3:16 pm 07/15/2013

    One of the main points of Gary Taubes’ research is that you cannot eat the right things by willpower alone. In order to fix your cravings and suppress your appetite for carbohydrates, you need to eat enough protein and fat for a long enough time to change how your body works. I immediately discount people who write about diet and say it’s about willpower, because it doesn’t need to be if you fix how your body is functioning!

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  9. 9. waltermatera 3:46 pm 07/15/2013

    A trenchant and clear article . . . reassuring, too. Yes, by all means, let there be moderation. It’s good for you.

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  10. 10. Owl905 4:04 pm 07/15/2013

    What’s the use of getting to the top of the food chain if it means eating more lettuce?

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  11. 11. Quantumburrito 4:21 pm 07/15/2013

    This is a great post, thanks.

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  12. 12. K S Rose 4:44 pm 07/15/2013

    While I found this article to be overall a good one, the summation seems to minimize the most important parts. Fructose found in raw fruits and veggies is fundamentally different than high fructose corn syrup because it is encased in fiber. Not only does the sugar from fresh fruit get released slowly in the system, the body uses more energy to break down those cell walls to get at the sugar inside and some may not be released at all. Highly processed foods, especially those that add high fructose corn syrup, leave you feeling hungry at the low levels they should be consumed at. I agree wholeheartedly that we need to be more active, but today’s jobs make that more difficult.

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  13. 13. DrDeborah 4:54 pm 07/15/2013

    Thank you for this cogent, well researched piece. I would suggest however, that you apply your same skills of research to your recommendations in the last paragraph. Currently leading the pack in comparative weight loss research are diets like the Atkins diet or the Paleo diet: plenty of meat, high in fat, and lacking in whole grains. You are hasty to spout the conventional wisdom about obesity (“Eat less, eat more of what we’ve been eating for decades, move more”), and I believe will change your tune if you apply the same research skills evident in your work on sugars.

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  14. 14. ecoligist 7:17 pm 07/15/2013

    Fructose and cavities! It’s been known for some years in bacteriology circles that fructose and sucrose, which is half fructose, cause oral bacteria to make lots of slime while other sugars such as glucose do not. This slime is a component of dental plaque. Isn’t it interesting that our candy-free apes in our zoos, have little tooth decay – only lots of broken and worn teeth from chewing on things they shouldn’t. These apes have the same types of oral bacteria as we humans have – mostly in the lactic-acid group (aka: the dairy bacteria, which are found in huge numbers in milk and go on to convert the cheeses. The dairy bacteria are “probiotic” in that they putatively kill other “bad” bacteria, but when fed fructose, they run afoul and make plaque.

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  15. 15. daviddriscoll 8:30 pm 07/15/2013

    The claims around fructose uniquely not affecting satiety also haven’t stood up to clinical trials (despite having some feasible mechanisms behind them!).

    We now have confirmation from the authors themselves (via the letters published in the Journal of the American Medical Association that the much misquoted study “Effects of fructose vs glucose on regional cerebral blood flow in brain regions involved with appetite and reward pathways” from January 2013 with regards to fructose and hunger – has been largely misrepresented.
    “We underscore that the study found no statistical difference between glucose and fructose ingestion on hunger, fullness, or satiety. Thus, while we also reported pre-drink vs post-drink changes in fullness and satiety for each drink separately, we did not interpret this as demonstrating a difference between treatments.”

    We also know from the supplementary data from the Stanhope 2009 study, that although MASSIVE doses of fructose resulted in a similar levels of fat gain (admittedly it was the more problematic visceral fat) that people taking in 25% of their calories from fructose vs glucose, didn’t eat any more calories under free living conditions.

    Also a recent rat studied suggests that it might be the sweet taste and NOT the fructose (as they used an artificial sweetener) although this article has been largely misquoted also!

    With regards to Dr Lustig and his fringe views on fructose, while theories and evidence may seem convincing to the general public and reporters, the real test is how well he performs with his fellow scientists!

    He was certainly called out for overstating the evidence and poorly extrapolating rat research at a conference he spoke at last year – check out the Q and A video in the attached article by David Despain (as well as the other lectures)! for a full review and links to all lectures – if not just watch the Q and A at and

    With regards to fructose and addiction? At the Q and A at the Sugar Symposium, Dr Lustig was called out on this and one researcher showed that rats liked glucose based carbohydrates over sucrose, and another questioned the applicability of rat research to be extrapolated to humans!

    The major issue with Dr Lustig’s theory is looking at US Sugar intake over history – levels were still high in the early 20th century – so saying it is sugar is either an oversimplification or there is a threshold value that we have recently crossed. Methinks that it is a perfect storm of more sugar and less burning it up with physical activity!

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  16. 16. korg250 12:15 am 07/16/2013

    Pro tip for a healthy life: go vegan!

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  17. 17. redpola 1:28 am 07/16/2013

    A great article, but I’m asking myself how it’s possible to write about the perils of sugar without mentioning John Yudkin and his recently-republished seminal work on this subject “Pure, White and Deadly”. It’s tragic how Yudkin was discredited by American non-scientists, yet here we are nearly 50 years later discovering the wisdom of his research.

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  18. 18. Walwyn 9:48 am 07/16/2013

    I think the Dr. Lustig is largely correct in his assessment of the risks of sugar. However, he and his like minded researchers and clinicians are now bearing the brunt of a concerted attack by the food industry and its shills to discredit the research. David Driscoll’s links are to a sugar “symposium” that on face value seems to discredit/tarnish Lustig’s research. Dig a little deeper and lo and behold we find that the Corn Refiners Association are the sponsor of the event. The corruption of science continues.

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  19. 19. Son of Liberty 12:35 pm 07/16/2013

    Great to see an actual science based article in SA

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  20. 20. David Cummings 1:10 pm 07/16/2013

    Excellent article. Very well done. And I very much agree with the conclusions of the last paragraph. Good health is complex and requires thoughtful care in many respects, not just in terms of sugar intake (though that is certainly a component).

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  21. 21. kienhua68 2:21 pm 07/16/2013

    The bottom line still remains that a balanced diet is key. Heredity also plays a significant role. My guess is no matter what the diet, those of our species that best adapt will prevail.

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  22. 22. RayCL 4:48 pm 07/16/2013

    This issue raises a concern I’ve had for years. I’ve personally witnessed two toddlers, half-siblings whose parents facilitated totally unrestricted access to boxes of “Juicy Juice”, which they consumed in amazing quantities as a result. Both of these young people developed type one diabetes. I am also aware of what appears to me to be a widely practiced bottlefeeding infants large amounts of pure fruit juices. There is no fiber involved in this consumption. After reading many, many articles on the sugar debate, I see no information to mitigate what seems to be a health hazard built into child rearing. If someone can point out the flaw in my reasoning, I would welcome it.

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  23. 23. LAToxDoc 7:30 pm 07/16/2013

    Not such a good article, in my view.

    The contention that fructose consumption in the United States is falling, after 30 years of dramatic increases, may be true in aggregate for the past 5 years, but the levels of fructose sales appear to have been fairly stable, and NHANES III suggests that fructose consumption may still be increasing among subsets of Americans. (See

    Furthermore, discussing fructose as “poison” is appropriate if one talks also about “dose,” which this article fails to do in much detail. (“Dose makes the poison.”)

    What Lustig and others have argued, and what this article does NOT discuss, is what happens to folks whose fructose intake exceeds 50 to 100 grams per day. Fructose consumption below this level appears to be handled safely by most people’s livers. But higher fructose doses overwhelm certain metabolic pathways and instead drive the carboxylic acid pathway, and the production of uric acid and fat precursors.

    Incidentally, just because fructose’s metabolic pathways have different rates in rodents than in humans does not make these “pathway” questions irrelevant. The author appears to be too quick to dismiss the importance of converting even 1% of every extra gram of fructose into fat. But at that rate, a person eating 150 grams of fructose every day for a year would gain 2 pounds of fat from that one pathway. Over many years, that weight gain would add a lot. Plus, if there are subsets of the population who metabolize fructose to fat even more readily than average, we could easily have subsets of the population whose obesity and metabolic syndromes were directly explained by their fructose consumption, even if on average humans are less susceptible to these adverse effects than rodents.

    Furthermore, population fructose consumption could perhaps be decreasing in the population as a whole, even as subgroups of Americans continue to consume fructose in amounts above 100 grams per day. For those subsets, the risks would persist despite what happened in the rest of the population. Accordingly, I would argue that mean fructose consumption in the population is, of course, interesting, but more interesting would be consumption at the 75th or 90th percentile.

    It’s disappointing that this article paid so little attention both to dose-response questions and to the possibility of epidemiologic variability in the American population.

    Notwithstanding the bland reassurances of this article, I’m still worried that fructose is a poison for too many Americans, whose daily dose of fructose remains too high. / Paul Papanek MD

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  24. 24. markbeadles 8:48 pm 07/16/2013

    A minor nit: you say “the sugars in their diet, which must have come from whatever plants and animals were available in a given place and season” but of course, other than milk there are _no_ animal sources of sugar; in fact the only significant animal source of carbohydrates of any kind is liver, in the form of the complex carb glycogen. I think this actually reinforces the point that simple carbohydrates were once much less available than they are now.

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  25. 25. dragunus 1:05 am 07/17/2013

    Your analysis for glucose & fructose over-use is correct but as most of the media, your info is behind the times. Are you aware of sugars/carbohydrates such as Mannose, Fucose and other such polysaccharides. Since the publication by Dr Robert Murray in the 24th Edition of Harper’s Biochemistry (Chap 56) where it goes to explain the importance of such sugars in the formation of Glycoproteins and the subsequent health implications, at the cellular level.

    And quite recently, in a report issued by the U.S. National Academy stating that “..the United States should make a broad push to improve the science of understanding sugars in order to enable widespread advances in medicine..” . The report goes on to say – “The report’s authors, led by David Walt, a chemist at Tufts University in Medford, Massachusetts, note that the role of sugars in living organisms is widely underappreciated. They are the fourth major class of biological macromolecules,”.

    Back in 2011, a study was published by the European Journal for Clinical Nutrition – The functional role of dietary carbohydrates in nutrition is one of the most complex and at times controversial areas in nutritional science. In-vitro and in-vivo studies suggest that certain dietary saccharide biopolymers can have bifidogenic and or immunomodulatory effects, and that some could represent preferential substrates or precursors that can impact cellular glycosylation.

    And this is just the tip of this ‘iceberg’ – the study of biological sugars in our bodies at the cellular level is on-going. if Scientific American are to discuss the topic of sugars, you cannot leave this area of study out in the cold. It does not do justice to this publication and the subject.

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  26. 26. Maureenataba 11:53 am 07/17/2013

    The major takeaway of this piece – moderation – is spot on. There was also recently an article in the New York Times that makes clear that balancing all calories (not just sugar) is critical to combating obesity and realizing a healthier America:

    -Maureen Beach, American Beverage Association

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  27. 27. ssm1959 12:41 pm 07/17/2013

    Over consumption is the first ill. However it has become far easier to over consume than ever before. When a 16 oz bottle of lemonade has the equivalent of 27 teaspoons of sugar we have gone around the bend. The problem with pointing all the fingers at sugar misses much of the problem in our current food system. Items that contain high refined carbohydrates also contain high concentrations of many other non-food components. Each of these individually is approved by the FDA but they are never looked at in combination. Much like the patient who has poly-pharmacy prescribed by multiple physicians, people eating a diet high in process foods may be experiencing a wealth of issues derived by the synergy between all the components taken together. The only viable strategy is to begin eliminating these components en masse. I have many patients who have found subtle improvements in their health by taking such measures. Of particular note is the issue of gastric reflux. If you are old enough to remember, this never used to be such a large problem prior to the 1990′s. Now people are surviving daily on OTC, H2 antagonists. I have found getting patients to reduce their intake of HFCS this issue moderates for most. Is the HFCS responsible for the problem? Probably not. but is serves as the marker most easily identified by patients that reduce a whole host of other components of their diet that may be the true cause.

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  28. 28. ferrisjabr 2:11 pm 07/17/2013

    @Bill_Crofut Cells developed an appetite for sugar as energy many hundreds of millions, perhaps billions of years ago, long before mammals and other complex multi-cellular lifeforms existed. We inherited that appetite from our evolutionary ancestors. Cells can get energy in a variety of ways with a variety of molecules with and without oxygen

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  29. 29. ferrisjabr 2:15 pm 07/17/2013

    @LDMAYA I think you have in fact misunderstood. I recommend reading this paper by Lustig and rewatching The Bitter Truth. He definitely thinks fructose specifically is a toxin. He clearly says consuming too much fructose is the primary cause of obesity and diabetes. And he thinks we should all return to consuming tiny amounts of sugar (which may in fact be a good idea for reasons unrelated to toxicity). Also consider this criticized paper by Lustig’s colleagues that attempts to show that glucose is benign while fructose is toxic

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  30. 30. ferrisjabr 2:17 pm 07/17/2013

    @K S Rose I agree these are important points and devoted a paragraph to them:
    “To properly understand fructose metabolism, we must also consider in what form we consume the sugar, as explained in a recent paper by David Ludwig, Director of the New Balance Foundation Obesity Prevention Center of Boston Children’s Hospital and a professor at Harvard. Drinking a soda or binging on ice cream floods our intestines and liver with large amounts of loose fructose. In contrast, the fructose in an apple does not reach the liver all at once. All the fiber in the fruit—such as cellulose that only our gut bacteria can break down—considerably slows digestion. Our enzymes must first tear apart the apple’s cells to reach the sugars sequestered within. “It’s not just about the fiber in food, but also its very structure,” Ludwig says. “You could add Metamucil to Coca Cola and not get any benefit.” In a small but intriguing study, 17 adults in South Africa ate primarily fruit—about 20 servings with approximately 200 grams of total fructose each day—for 24 weeks and did not gain weight, develop high blood pressure or imbalance their insulin and lipid levels.”

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  31. 31. ferrisjabr 2:20 pm 07/17/2013

    @DrDeborah Although I largely disagree with the logic of the Paleo diet, I think most of the recommendations would be smart choices for many Americans. Indeed the “conventional” USDA’s advice and the Paleo diet have a lot of overlap: they both suggest eating more veggies, fruits and lean proteins; the main difference is that Paleo dieters exclude grains, legumes and dairy, which I do not think is justified by the evidence. People should eat less energy-dense carbs and starchy foods bc they are dangerously tasty and easy to eat too much of, not bc sugars, grains or carbs are toxic

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  32. 32. ferrisjabr 2:35 pm 07/17/2013

    @LAToxDoc Although I did not explicitly state that “the dose makes the toxin,” I was very clear about the difference between animal/a few human studies using 100 to 300 grams fructose / day finding ill effects vs reviews of typical consumption not finding these effects. You seem to be particularly concerned with “subsets” of the population that consume very high amounts of fructose. I agree this is a concern, which is why I write ” A small percentage of the world population may in fact consume so much fructose that they endanger their health because of the difficulties the body encounters in converting the molecule to energy. But the available evidence to date suggests that, for most people, typical amounts of dietary fructose are not toxic.” However I do not think that what is true for a small percentage of people should be used to guide or scare everyone else. Even the top 10% highest fructose consumers in the country are getting between 75 to 130 g fructose / day, not 150 and not 300. It’s possible these people are directly harming themselves but they are not the majority – not even close – and are not a reason for most people to worry.
    Bottom line: for most people typical levels of fructose are not toxic (see, I do address the dose)

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  33. 33. Bill_Crofut 8:55 am 07/18/2013


    Re: “Cells developed an appetite for sugar as energy many hundreds of millions, perhaps billions of years ago, long before mammals and other complex multi-cellular lifeforms existed. We inherited that appetite from our evolutionary ancestors.”

    Those are assertions. What is the evidence to substantiate them?

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  34. 34. ironjustice 7:52 pm 07/18/2013

    It has been shown iron and sugar interact.
    “Cross-Talk Between Iron Metabolism and Diabetes
    It has also been hypothesised the amount of iron in the human body accumulates over time leading to what is now known as ‘age related iron accumulation’ to explain this accumulation of iron , in technical terms. This accumulation of iron was hypothesised over thirty years ago by one Dr. Jerome Sullivan of the ‘iron hypothesis’ fame.
    He discovered iron to be only second to smoking for identifiable cause of heart disease. Now when one considers this fact , iron accumulation and the ready supply of refined sugars , one is left with a combination of iron AND sugars which leads to a very high rate of disease , as evidenced by Inuit who were followed over a period of time and were found to develope diabetes when exposed to highly refined sugars AND their increased iron load as opposed to those who began with lower iron levels BUT still had the same diet of highly refined sugars. The high rate of obesity and hunger is due to the fact man is a herbivore eating meat which leads to the iron levels unhealthy in man.
    Cites available upon request.
    “Diabetes in Unmmannaq was higher than that in the towns of Nuuk and Qasigiannguit”.

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  35. 35. ironjustice 8:04 pm 07/18/2013

    “The most conservative approach would be to place the burden of proof with those who maintain that any stored iron is safe”

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  36. 36. sunnystrobe 8:29 am 07/19/2013

    Very interesting how the gorilla in the room ain’t seen! It answers to the name: ‘Addiction’!
    Recent research has shown how our brains’ ‘addiction center’ are brightly lighting up when, whoosh! sugarsugar enters the fray.
    And yet, the vested interests capitalizing on this our pandemic human predicament are still bleating piously about ‘moderation’, blaming other drugs, and the victim,rather than their overdosing for the medical disasters following.

    It’s the medical doctors at the coalface that take an unblinkered view . They are not to be envied!
    A propos: apples: a wonderful diet advice indeed! To be taken before meals, it lowered my blood pressure, my bodyweight, my cholesterol, and my propensity for colds.

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  37. 37. hastigo 4:38 pm 07/22/2013

    Very nice review. Well balanced.
    Thank you.

    jamesT. MD

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  38. 38. bucketofsquid 5:52 pm 07/23/2013

    I turned into an enemy of high fructose corn syrup when I bought a bag of beef jerky and a bag of dried blueberries and discovered that both were coated in high fructose corn syrup. Seriously? To desecrate 2 such wonderful foods in such a way is outright evil. Before then I liked high fructose corn syrup.

    On a lighter note, I watched a show about calories in alcohol where they stated that alcohols are a type of sugar. Right after the show was a corn growers commercial where they concluded with “sugar is sugar”. I’d like to see them sweeten their children’s meal with Jack Daniels and see how long it takes for Child Protective Services to show up.

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  39. 39. energyforthebrain 9:53 am 07/27/2013

    Indeed, our brain is hardwired to be biased toward sweet taste, this is how it controls our entire energy metabolism and this is how it still tries to rule no matter how severe we change (deform) the environment. The good news is, the more we understand, the better we adjust and correct. Well, hopefully. In case it does make sense, you might want to read a free full text by googling for doi: 10.3389/fnene.2011.00008 or for “Carbohydrate-biased control of energy metabolism: the darker side of the selfish brain”

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  40. 40. jwillis84 3:20 am 08/2/2013

    I didn’t expect the article to cite studies funded by a major Processed Food manufacturer.. and dispute credentialed professionals and simple chemical formulas with innuendo. The article seemed more of a stirring of the pot rather than an informative presentation.

    I appreciated the slight history lesson, but following that up with empty statements were not very satisfying.

    The only hard statement I could grasp was.. the research animals do not process fructose like humans do. I would have appreciated a solid citation and a real analysis of the experiment to compare to previous work.

    The blending of “self control and portion control” issues were also blurring the lines of absolving sugar or fructose as the key to avert obesity. I don’t see how those can be relevant if they are not “responsible” at least in part..

    The statements seemed like an attempt to say “they may be part of the problem, true.. evidence accepted” by the author.. then diverted with “but they aren’t all of the parts of the problem”

    It left me thinking.. this was more a debate to be won, rather than a fact based delivery of a message.

    And being a debate.. the truth was not at issue.. and more of a liability.. since the goal is more to convince the reader of the thesis..even if it is know to be wrong.

    I hope I stirred the pot using the same mechanisms, just as well.

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  41. 41. AshbyM 1:24 pm 08/6/2013

    Almost as a throwaway, you cite this article:

    …which indicates that high glycemic index/GL diets are positively correlated with Type II Diabetes, coronary heart disease, breast cancer, etc.

    “Low-GI and/or low-GL diets are independently associated with a reduced risk of certain chronic diseases. In diabetes and heart disease, the protection is comparable with that seen for whole grain and high fiber intakes. The findings support the hypothesis that higher postprandial glycemia is a universal mechanism for disease progression.”

    That seems to dovetail nicely with Taubes thesis that excess carbohydrates are driving obesity, Type II diabetes, heart disease and even some cancers.

    The conclusion then includes some standard bromides about how all calories should be counted and the assumption that heart disease is driven by the fats associated with consuming the sugars, an exhortation to “Get out and exercise!”, watch salt, etc..

    I don’t think either Taubes or Lustig would argue that a moderate intake of sugars is toxic (particularly in the form of vegetables or whole fruit), but then the question is…what is moderate?

    After reading Taubes books and articles and listening to Lustig’s video, I drastically reduced my intake of sugars/carbohydrates. I did not significantly reduce my caloric intake. I ate plenty of non-starchy vegetables and meats (with the fat on), eggs, whole fat dairy (cheeses & plain yogurt) and nuts. Over the next two months my weight dropped by 30 lbs, my elevated triglycerides and bad cholesterol dropped, my blood pressure went from 126/80 to 110/70.

    I enjoy exercise and think it is good for you physically and mentally, but not primarily for weight loss purposes. Five years ago I was cycling to work, a commute of 20 miles with hills almost every day. I only lost 17 lbs, despite my high levels of activity, because exercise makes you hungry. When my knee went (from an old sports injury), my weight rapidly increased right back up to the starting point. Consequently, my sole exercise during my low carb experiment was walking around the block before lunch (about one mile). Despite this modest level of exercise, I dropped thirty pounds in two months. In my late forties, I’m reasonably close to my healthy weight from my early twenties.

    I have now kept that weight off for two years, simply by restricting carbohydrates.

    The obesity epidemic has coincided with the low fat dietary fad. The low fat junk science hasn’t helped societal rates of obesity or heart disease. Our entire food supply has been shifted toward sweet and away from fatty. I think this has probably been counterproductive.

    Avoiding excess sugars and carbs, eating low glycemic index/load, functionally it’s very similar. Sugar in low levels of concentration and consumed in moderation isn’t toxic, but if you would like to lose weight and improve your health, kicking the sugar habit and limiting carbs is a great place to start.

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  42. 42. retroarama 7:31 pm 08/7/2013

    It may be hard to swallow but once upon a time sugar was not the unhealthy villain it is viewed today but an “essential” nutrient. Through the first half of the 20th century sugar was deemed essential to health-good tasting and good for you. In fact it was sanctioned by Uncle Sam as part of the 7 essential food groups of WWII. No one fanned the sugar flame more than Corn Products Refining Co. producers of dextrose sugar whose ads encouraged “By all means. let em’ eat cake…and candy too! Dextrose was the wonder nutrient. For a look at a collection of vintage Dextrose ads whose messages seem as quaint as the images themselves

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  43. 43. JuliaABQ 3:30 am 08/9/2013

    This article fails to mention the studies that have been done regarding the interaction of fructose and leptin. Leptin is a hormone produced in the stomach that signals the brain that it’s time to stop eating. Fructose inhibits the production of leptin.

    In people of normal weight, this is not an issue. However, studies show that clinically obese people have much lower levels of leptin than non-obese people. If you have less leptin to start with and then routinely ingest fruit as part of a weight-loss diet, you are simply making it more difficult to follow the plan.

    I was skeptical, but I found that when I significantly reduced the fructose in my diet by eliminating fruit juices and most sweet fruit, for the first time in my life I actually felt full from a normal portion of food. It was a revelatory experience for me. For four decades, I had never had that feeling unless I had eaten an absolutely huge “Thanksgiving dinner” type of meal.

    I do continue to eat some fruits, particularly dark berries and tart fruits that contain less fructose, but I can tell when I’ve gotten too much fructose back into my diet (usually hidden in prepared foods), because I no longer get that “time to stop” signal.

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  44. 44. HeatherT 3:25 am 08/13/2013

    Dr. Richard Johnson and company have done a lot of research on this, and it’s somewhat more subtle than “sugar is bad”. Fructose … and some other foods … raise uric acid levels. Uric acid levels trigger fat storage, esp. for hibernation or for taking advantage of seasonal surplus calories. What was interesting to me was seeing how the traditional Japanese diet (centering on rice, tea, sake, and fish) is a low-uric acid diet, while the Sumo diet (centering on wheat noodles, beer, saturated fat and meat) is a high-uric-acid diet.

    Anyway, as an experiment and to help my sore joints, I went on a low-uric-acid diet, including lower levels of fructose. Voila! I’ve lost 40 lbs so far, and my joints feel great. Same thing happened to my Dad … he went on a low-purine diet to help his gout, but immediately lost weight too. He never did eat much sugar, but swapping the meat for fish he lost the gout, and he lost the weight.

    “Moderation” for one person is “extreme” for another though. My diet would have been considered “moderate” by most, but my diet now works a lot better.

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  45. 45. JenniferC 10:45 am 08/14/2013

    My understanding is that Steve Jobs considered himself a “fruitarian” and most of his diet for a time period was fruit-based. And he died from pancreatic disease. So perhaps fructose overloaded his pancreas. All things in moderation is a good way to live.

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  46. 46. joae996 1:52 pm 08/20/2013

    Interesting article, and good science, which expertly demystifies the demonization of sugar, in general. However, it also seems to suspiciously minimize the impact of two things… high fructose corn syrup, which by many measures has had a massive negative effect in the United States (one of the few countries that allows its use in human food).

    The article minimizes obvious truths with assumptions that are not borne out in observation. For instance, the argument that 300 grams of the sugar would be equivalent to 8 cans of coke, and nobody drinks that is a laughable assertion. A can of coke is 12 ounces. The current standard size everyone gets from Seven Eleven and Circle K of soda is 44 ounces. That’s almost 4 cans of the stuff in one drink. Yes, they have a 32 ounce cup, and some even have a 24 ouncer, but have you ever just stood and watched? Nobody buys the smaller size. As long as the child is strong enough to heft the 44 ouncer, that’s what they get. And all the adults get that, or even the larger 64 ounce mega cups, which is more than 5 cans of soda.

    Now, the average fat American will have at LEAST one of these a day, plus sodas at lunch, with constant refills. My work lunches see two to five refills of a glass, which is approximiately the size of a soda can. While I have tea, many of my coworkers have soda. So, that’s another 2 to 5 cans of soda at lunch, on top of the thirst buster on their desk they’ve been nursing all day.

    Top this off with several candy bars, or other high sugar snacks loaded with HFCS during the day, whatever was in the actual food eaten, plus the other forms of sugar in that food, and we haven’t even gotten to dinner, that desert, the after dinner snack in front of the TV, or that snack you had at 2am because you could not sleep.

    I’m really not sure what study claims the average person eats only 100 to 150 grams a day, but this study is highly flawed. My analysis is average for all the people around me. Even those who are very health conscious in certain ways, still manage to pound down the sugar. One who avoids gluten and eats all manner of hippie foods still gets the 44 ounce energy drink/gatoraid mix every single morning, and will usually go get a second one at lunch. He’s easily over the 300 grams mark. And the average worker that isn’t trying to buy laughable protein bars (loaded with more HFCS than a Snickers), are eating the snickers or M&Ms, or other foods like that faster than you’d believe they can unwrap them.

    This is where this article totally breaks down. While I believe it’s argument that, in general, the sugar itself is not the villian, the massive amount of HFCS which is HIGHER in Fructose, which the article itself says is harmful to us if we over do it, is the lead cause here. The only thing in the article claiming otherwise is a bogus claim that people don’t actually eat that much sugar… which simple observation says is bunk.

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  47. 47. sofistek 6:34 am 09/18/2013

    The author doesn’t appear to have contacted the scientists he references, though he does quote a couple of those who might be considered critical of Robert Lustig’s work. So I’m not sure this is a well researched article. I would like to have seen specific reasons why the processes described by Lustig in his Sugar: The Bitter Truth video are wrong. Lustig can back up his position with research purely on humans, though I worry about much health research as it is mainly funded by the very companies who stand to lose out from Lustig’s comments.

    I’d also disagree that moderation is the keyword. If something is toxic, it’s toxic, period. Why eat toxic foods in moderation? We certainly need to eat fresh unprocessed and unrefined foods – so fresh meat and vegetables, primarily – prepared in our own kitchens. A word of caution on whole grains (and seeds); yes, they are nutritious but only with correct preparation. Most grains and seeds contain a lot of phytic acid which is there to prevent digestion (after all, the seed wants to germinate in the ground, not be digested in a stomach), so to get the benefit of that nutrition, soak most seeds/grains overnight or sprout them or ferment them.

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  48. 48. ABlack 7:40 am 01/29/2014

    in a way it’s kid of irrelevant because people will continue to consume it no matter what.

    Logged in as :

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  49. 49. wvugirl 3:40 pm 02/9/2014

    This article raises a lot of concern. I believe that sugar can be harmful to your body in excess but at the same time, as stated above, we need it for energy. We need energy to power cellular and body functions. What happens if we don’t intake enough glucose where will we get it then? The body can also break down fat if needed but relies mostly on glucose to power movement and physical activity. We all know that there are different sizes of sugar and some take longer to break down then others due to their large chemical structure. We use glucose as energy to power muscle contraction for our everyday activities. My concern is that when we do intake to much glucose then we are adding more mass to our body that in return could be harmful. When you increase your body mass then there needs to be an equal and opposite force supporting you. These forces, if strong enough, can be harmful to joints and vasculature. In conclusion I do not agree with the statement that glucose is toxic. I believe it can be harmful in excess but it is needed for cellular functions.

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  50. 50. markedjar 1:38 pm 02/26/2014

    Excellent summary of the research and history of sugar. There are so many pathways by which refined sugar can have negative health effects ( I think you hit the nail on the head — the best way to avoid refined sugar is by eating whole foods!

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  51. 51. everyrosie 12:43 pm 05/9/2014

    Sugar, especially how much sugar the average American eats, is one of the worst things for you. It’s so tough to avoid though! Like you mentioned, it’s in everything. Even bread! I think the FDA should make sugar consumption its number one priority.

    Rosie | South Shore Therapies

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