“We are exuberant users of dietary supplements in the United States,” Coates explains. Yet because manufacturers of these products do not necessarily have to prove that their product is safe or effective before it hits the market, sales of dietary supplements far outdistance the research we have about them. In fact, says Coates, we spend 100 times more money to buy these products than we do researching them.
By definition, a dietary supplement is intended to supplement the diet. It can be anything from an herb to a nutrient to a “zoochemical” — an animal-based product such as bee pollen or creatine. We need to remember that a dietary supplement is just that: It adds to what may be missing in our diets. It does not replace healthful foods.
Some dietary supplements have been well studied, according to the Office of Dietary Supplements at the National Institutes of Health (https://ods.od.nih.gov/). Calcium and vitamin D, for example, can help maintain bone strength if one's diet lacks these nutrients or, in the case of vitamin D, if sun exposure is limited. By the way, both animal-based (D3) and plant-based (D2) forms of vitamin D are equally effective, according to Dr. Johanna Dwyer, a prominent nutrition expert at Tufts University.
Folic acid, a B-vitamin, protects against serious birth defects when women of childbearing age get 400 micrograms daily from dietary supplements and/or fortified foods. And omega-3 fatty acids from fish oils can lower blood triglyceride levels and may help guard against heart disease.
More is not always better, however. Excess vitamin A, for example, can bring on headaches, liver damage and birth defects in pregnant women. And “natural” products are not necessarily more safe. Naturally poisonous mushrooms can kill you.
We seem to have this idea that only prescription medicines have unwanted side effects. Yet anything we put into our bodies will affect us in some way. Dietary supplements have active ingredients, too.
For example, St John’s wort — a plant-based dietary supplement — has shown in a few small studies to ease the effects of depression. It can also increase one’s sensitivity to sunlight and weaken the intended action of several medications including antidepressants, contraceptives and anticoagulants, say researchers. Certain herbs such as comfrey and kava can cause liver damage.
Find more facts about dietary supplements at www.ods.od.nih.gov.
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(Barbara Quinn is a registered dietitian and certified diabetes educator affiliated with Community Hospital of the Monterey Peninsula. She is the author of "Quinn-Essential Nutrition" (Westbow Press, 2015). Email her at to barbara@quinnessentialnutrition.com.)
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