This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Earlier this week, I started a series of posts about what people should consider when they embark on a gluten-free diet for reasons other than celiac disease, such to alleviate symptoms of a gluten sensitivity.
My first post was on folate, an important B vitamin that appears to be less prevalent in gluten-free grain products when compared to their gluten-containing counterparts.
Another important nutrient that can be harder to get on a gluten-free diet is fiber.
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Fiber is one of three main types of carbohydrates, the other two types being starch and sugar. Fiber is present naturally in plants, but unlike starch and sugar, this carbohydrate is not digested as it passes through our system [2]. In the diet, it typically comes from fruits, vegetables, nuts and whole grains [2].
Not digestible doesn’t mean not important though; the Dietary Guidelines for Americans classify it as a nutrient that needs to be increased in the American diet. The current guidelines suggest 25 grams of fiber per day for women and 38 grams per day for men – and note that the average person gets only 15 grams per day.
The reasons? The guidelines cite fiber’s role in a healthy digestive system and note that it may help reduce the risk of diseases like obesity, type 2 diabetes and cardiovascular disease. Fiber may also play a role in reducing colorectal cancer risk, though evidence is not conclusive [2]. Other components of high fiber foods may be providing the benefits, so the American Cancer Society recommends a diet made up of a variety of high-fiber foods, such as whole grains.
Without the ability to eat some of these whole grains, such as wheat, do gluten-free eaters get enough fiber?
A search of the literature turned up only a few studies on fiber and the gluten-free diet. In addition, these studies only looked at people following a strict gluten-free diet due to celiac disease, so fiber intake could differ for people choosing gluten-free diets for other reasons.
A small 2005 study in the Journal of Human Nutrition and Dietetics surveyed 47 people with celiac disease on a gluten-free diet. The study found the majority of males consumed enough fiber, while over half of the females did not, based upon a 2002 American Dietetic Association recommendation of 20-35 grams per day for healthy adults. Interestingly, though the participants consumed less fiber than recommended, they consumed more fiber than participants from a study geared at the general population – the U.S. National Health and Nutrition Examination Survey. The small size of the study may have limited the accuracy of it’s results, however. A slightly larger study looked at the gluten-free diets of 137 people with celiac disease in the United Kingdom. Women in this study had lower intakes of fiber compared to a study of women with a variety of dietary patterns– the United Kingdom Women’s Cohort Study.
Why might the gluten-free diet be low in fiber? The American study cites one of the other three carbohydrates, starch, as a possible reason. As I mentioned in my folate blog, many gluten-free versions of foods, such as breads or muffins, replace gluten-containing grains with starch. These starches – such as rice, corn, tapioca or potato starch – contain little to no fiber [3].
So while following a gluten-free diet doesn’t necessarily lead to a low fiber intake, it’s worth thinking about how you will get enough of this nutrient, if you’re planning to go gluten-free.
Fiber can be found in whole grains that don’t contain gluten, including quinoa, buckwheat, teff, millet, amarath, and brown rice. (Check out this Mayo Clinic article that shows you how to cook them and add them to your diet). For example, a cup of cooked quinoa contains about 5.2 grams of fiber. That’s about the same as the amount of fiber in 2 and a half slices of whole wheat bread. A cup of cooked brown rice contains less, around 3.5 grams of fiber, but might be easier to find then some of the more unusual gluten-free grains. Other high-fiber foods include beans or peas, which range from 5 to 9 grams of fiber per serving (1/2 cup), depending on the type[1].
References
U.S. Department of Agriculture and U.S. Department of Health and Human Services. (2010). Dietary Guidelines for Americans, 2010. Washington, DC: U.S. Government Printing Of€fice. Retrieved from http://health.gov/dietaryguidelines/dga2010/dietaryguidelines2010.pdf
The American Cancer Society 2010 Nutrition and Physical Activity Guidelines Advisory Committee (2012). American Cancer Society guidelines on nutrition and physical activity for cancer prevention. CA: A Cancer Journal for Clinicians, 62 (1). doi: 10.3322/caac.20140 Retrieved from http://onlinelibrary.wiley.com/doi/10.3322/caac.20140/full
Thompson, T. Folate, iron, and dietary fiber contents of the gluten-free diet. Journal of the American Dietetic Association.100(11). Retrieved from www.ncbi.nlm.nih.gov/pubmed/11103663