take five to 10 grams of vitamin C every day, you have a much higher risk of having kidney stones, calcifications in your kidneys, or some other problem.” Vitamin E, an antioxidant naturally found in nuts and vegetable oils, is another example. In recent years, vitamin E supplements containing megadoses of the nutrient have been purported to prevent heart disease and cancer. But in October, a large federal study revealed that not only are these supplements not effective in preventing prostate cancer, they were likely to increase cancer risk—men who took daily vitamin E supplements increased their risk of developing prostate cancer by 17 percent. Though researchers stopped the trial when they discovered this adverse effect, cancer cases kept increasing for several years after participants ceased taking the supplements. The danger with supplements, says Caballero, is that it’s much easier to ingest a toxic amount of a vitamin by taking pills than by eating. For example, the National Institutes of Health Office of Dietary Supplements reports that vitamin E supplements contain anywhere from 100 to 1,000 IU per pill. You would have to eat more than four cups of almonds to get a mere 100 IU of vitamin E. (The recommended daily intake for adults is 22.4 IU.) Additionally, in developed nations like the United States, many foods are fortified. You already may be consuming more nutrients than you think. It’s also tricky to define toxic levels. Maximum levels of nutrients haven’t been studied in depth because researchers can’t give people a known overdose just to see what will happen. It may also take a long time for adverse effects to appear. Instead, the Institute of Medicine specifies a recommended daily intake and an upper level (the maximum amount you can safely consume without adverse effects). Caballero notes, “For some nutrients, the distance between the recommended intake and the upper level is relatively narrow, maybe 4 times, 5 times. And with supplements and fortification one could potentially reach that.” Regarding the most popular supplement, the daily multivitamin, Caballero says if you take only the recommended daily dose, it’s unlikely that you’ll get a toxic amount of any one nutrient, but it is likely a waste of money. Because in a pill you are taking all the nutrients at the same time, you are creating competition for absorption in your intestines, which diminishes the vitamins’ potency. “I don’t think it’s a danger, considering 52 Johns Hopkins Magazine • Winter 2011
the doses of Centrum and all these typical multivitamin supplements. It’s just [producing] expensive urine,” he says. “However, you should not assume that taking supplements gives you a benefit that replaces having a healthy balanced diet and being active regularly. To reduce your risk of cardiovascular disease or diabetes, you need years and years of healthy diet and activity. Unfortunately, that’s the way it is.”
Soy—Miracle Food or Hazard?
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everal years ago, its promoters touted soy as a miracle food, a low-fat, no-cholesterol source of protein. Researchers thought it might decrease breast cancer risk, minimize the effects of hot flashes, and increase bone density in women. Then came a “soy backlash” (as one reporter described it), with people saying that not only is soy not miraculous, it’s dangerous. Soy foods are fine, but soy supplements bear watching, says Bruce Trock, SPH ’87 (PhD), director of the epidemiology division at the Brady Urological Institute. “None of the studies that have looked at just normal dietary consumption of soy foods have given any indication of risk,” says Trock. “So as long as people are trying to get their soy from the diet—eating things like tofu, soy milk, soy nuts, miso soup—I think it’s unlikely that they’re going to risk any harm from that. And there may be benefits.” A study presented at the American Association for Cancer Research earlier this year, which looked at data from more than 18,000 breast cancer survivors, concluded that women can eat soy foods without increasing their risk of cancer recurrence. But soy supplements can be dangerous, Trock says, because a lot of them are highly processed, which might actually change the biological activity of the soy product. In several animal studies, soy supplements caused an increase in tumor growth; another study found that the more processed the soy product, the more it increased the growth rate of tumors in lab animals. And with supplements, it’s possible to get individual nutrients in very high amounts and in different proportions than you would get from eating soy foods. “There’s a reason these things are called micronutrients. They’re things that our bodies need in very small quantities. And they don’t just work singly, they work in combination, so often it’s not just