Americans spend about $28 billion a year on dietary supplements. “As Americans, we think more is better, but that’s not the case with vitamins,” says Dee Sandquist, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics.
Vitamin E. The National Cancer Institute was so hopeful that vitamin E supplements would decrease rates of prostate cancer that in 2001 it funded a study designed to test the theory. Instead, the findings revealed that the men who took vitamin E were 17 percent more likely—not less—to develop the disease. While vitamin E is a key player in immune function and cell communication, it’s best obtained through diet—in foods like wheat germ, sunflower seeds, and broccoli—and worst when taken regularly in high doses. Like many vitamins, it appears to lose its main benefits when taken in excess.
Vitamin A. Found in both animal and plant-based products, it’s also important for reproduction, bone health, and immune function. Supplements can be important for people with certain conditions that hinder fat absorption, including Celiac disease, Crohn’s disease, and pancreatic disorders. But vitamin A deficiency is uncommon among healthy Americans. And partly because the nutrient can build up to toxic levels in the body, taking more than you need over time can lead to serious liver problems, birth defects, and disorders of the central nervous system.
Vitamin C. From orange-flavored chewables to Emergen-C packets, mega-doses of vitamin C are staples in many American medicine cabinets. While the natural form of the vitamin supports immune function, there is only a weak scientific link between regular use of vitamin C supplements and shorter or less severe colds. Unlike vitamin A, vitamin C is water soluble, which means that if you take more than your body can use, the excess is usually excreted without causing harm. However, adverse reactions like diarrhea, cramps, and nausea can occur.
Written by: Anna Miller