When Tom Brady led the Patriots to yet another Super Bowl in February, it was inevitable that fans would speculate about how he could perform at such a high level at the “advanced” age of 41. One reason, as he explained in his book The TB12 Method: nutritional supplements galore, including a multivitamin, vitamin D, vitamin B complex, an antioxidant, essential fish oils, protein powder, a probiotic and electrolytes.

He’s not alone in the athlete-as-nutrition-consultant game. Colin Kaepernick, Shalane Flanagan and plenty of other superstars of sports have endorsed supplements of all kinds, implying that these, not just impeccable genetics and hard work, are significant factors in their success.

Surprisingly, 75 percent of people in the United States believe that it is beneficial to take higher doses of supplements than is recommended because it will lead to increased health benefits. At first glance, it is difficult to believe that taking a multitude of vitamins and minerals, antioxidants and protein could be concerning. After all, their prevalence in athletes, the military and older individuals is hard to ignore.

However, taking excess quantities of vitamins is unnecessary and can even be harmful. Best case scenario: water-soluble vitamins like vitamin B complex and Vitamin C are simply flushed out of your system if consumed in surplus. In fact, the president of the Australian Medical Association went so far as to say multivitamins just serve to create “very expensive urine.”

The worst case: too much vitamin consumption can be harmful to the body. For example, excess vitamin C or zinc can lead to gastrointestinal issues; too much Vitamin B-6 can cause nerve damage over time; vitamin A can cause headaches and liver damage; and regular high doses of vitamin D can lead to heart problems. There are certainly numerous essential benefits that vitamins and minerals provide, but larger quantities are not necessarily more beneficial. There is an optimal dose beyond which vitamin intake can even be harmful.

Another problem is that supplements often contain multiple ingredients and at differing amounts. Because ingredients react differently when combined, and those combinations have not been studied, it is challenging to guarantee their safety and efficacy. Studies have actually shown that supplements with multiple ingredients are associated with more severe adverse effects.

To compound the problem, ingesting combinations of different dietary supplements, or combining supplements with medications can lead to unintended side effects that are difficult to predict. Cimetidine, a drug used to treat duodenal ulcers, can slow the rate of caffeine removal in the system and inadvertently increase the side effects of caffeine consumption. Even antioxidant supplements, such as vitamins C and E, can potentially reduce the efficacy of certain types of chemotherapy

Additionally, many people do not share their list of supplements with their physicians, which can lead to physicians prescribing drugs that could react with those supplements. Such instances can cause drug complications ranging from decreased efficacy of antidepressants and birth control pills to reducing the blood-thinning effect of blood clot medication. It is no wonder then, that almost a third of poison control center calls associated with dietary supplements report adverse reactions, and that an estimated 23,000 emergency room visits are attributed to adverse events with supplements every year.

Consumers serious about optimizing their health should think critically about the sources they use for supplement recommendations, rather than choosing products touted by elite athletes. Looking at reputable sources of information can help us answer questions about the benefits and warnings of supplements.  Consulting with nutritionists and your health care providers is also important for finding the most efficient and safe supplements to aid your well-being and optimize performance.

On one hand, it is consumers’ responsibility to do due diligence and seek out information on the supplements they choose to aid their wellbeing. On the other hand, athletes should use caution in advertising supplements to their fans because it can lead to adverse effects. To date, neither group is holding up its end of the bargain.