During the past 25 years dietary supplements have rocketed in popularity in the U.S.A., reaching over $25 billion yearly in sales. Contributing to a misguided air of authenticity, they are offered in drugstores, supermarkets, and health-food stores. But what do we actually know about these products in terms of both safety and efficacy? In a 2013 Consumer Reports survey, 55% of respondents thought the government required supplement makers to include warnings about potential dangers and side effects on their products. They don’t, meaning that safety issues are often ignored!
So let’s run down a list of highly popular supplements, and the pros and cons for each:
Multivitamins: Many people believe they can promote general health and ward off serious conditions such as cardiovascular diseases and cancer. But the facts don’t support these contentions. Clinical trials repeatedly fail to show benefit of multivitamin supplements to healthy people. But even worse, they can, under certain circumstances, be risky: Both vitamin A and calcium can be dangerous if taken in excess, especially when added to a normal diet. Adult males and females should not ingest a daily total of over 3,000 mg. of vitamin A. Total daily calcium intake should not exceed 2,500 mg. So check to see how much you are getting in your regular diet and avoid supplements that cause the totals to exceed these levels.
Vitamin E: Originally touted to prevent cardiovascular disease, later studies have totally debunked this premise. More recently, supplements of vitamin E were suggested in the hope of preventing prostate cancer, but actual study pointed in the opposite direction: This vitamin actually increased prostate-caner risk in men age 50 and older.
B vitamins: Often thought to promote healthy metabolism and energy, the evidence refutes this contention in most circumstances. A normal diet contains an excess of B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (Pyridoxine), B12 (cobalamin), and folic acid. Unless your diet is deficient (see below), then supplementation is a waste of money. Vegetarians, and people (especially the elderly) having difficultly with absorbing B12, may benefit from supplementation of this vitamin. Moreover, women who are or may become pregnant should consider supplementation with folic acid, 0.8 mg daily. The oral form of supplemental folic acid is usually absorbed better than that found naturally in food. One caveat, however, is that high doses of folic acid can mask B12 deficiency that can lead to serious physical problems.
Vitamin K:Believed to promote healthy blood clotting and protein synthesis and prevent cancer. The reality: Leafy greens and other vegetables provide more than enough to satisfy the body’s need for this vitamin. Moreover, the normal bacteria that inhabit the bowel synthesize vitamin K and can make up any possible shortfall. There is no evidence that supplemental doses can prevent cancer. But there is a downside risk: Too much vitamin K can make the anticoagulant (blood thinning) drug warfarin (CoumadinR) less effective, a serious potential danger.
Fish Oil: This supplement is widely used with the intent to prevent and/or treat cardiovascular diseases. Although the evidence indicates that two or more servings of fish weekly is capable to reducing heart attacks and strokes, linking fish oil supplements to these diseases is less clear. Some evidence suggests that they may help, but the better choice is in the dietary consumption of the fish itself.
Calcium: An important mineral constituent of the body, calcium is often taken with the intent of building healthy bone, thus preventing osteoporosis and fractures. But the evidence does not support such claims. Even with supplemental consumption of over 1,000 milligrams daily, calcium has not been shown to prevent fractures in either premenopausal or postmenopausal women. Among the possible risks of high calcium intake, some studies suggest that it may increase the risk of heart disease.
Vitamin C: For many years high doses of this vitamin have been used for preventing and treating colds, heart disease, and cancer. Despite numerous studies, however, the actual evidence fails on all these counts. Although generally safe, a possible risk of high doses of supplemental vitamin C can lead to unhealthy buildup of iron in body tissues and organs, posing a risk to the occasional individual suffering from iron storage disease (hemochromatosis).
Vitamin D: This vitamin is important in bone and muscle health, nervous and immune system function, cell growth and reproduction, and moderating inflammation. Although controversial, its administration is alleged to ameliorate certain types of heart disease, hypertension (high blood pressure), diabetes, and possibly multiple sclerosis. Some research suggests it may prevent colon cancer, and—although controversial—other cancers as well. It’s also associated with a reduced rate of depression in older people, and greater immunity against some infections. So far, however, few controlled prospective trials have investigated the potential benefits of vitamin D supplementation in preventing any of these problems.
Normally we obtain vitamin D through sun exposure and dietary intake. It is manufactured by the body, but the process requires exposure to ultraviolet light. Given the widespread use of sunscreen, however, to prevent skin cancer, up to 36 % of Americans are low on this vitamin. Food sources for this vitamin are limited, although some products such as milk are fortified. Natural sources include fatty fish such as catfish, salmon, mackerel, sardines and tuna; eggs; beef liver; and cod liver oil. Your doctor can perform a blood test to determine whether you are deficient of this vitamin. If you are found to be deficient, instead of risking sun exposure, dietary modification and/or supplemental vitamin D should be considered.
The latest US recommendations for the minimum daily requirement of vitamin D, or cholecalciferol—vitamin D3, the preferred form—are 600 IU (international units) for those under 70, and 800 IU for those older. These quantities appear to retard bone loss. Persons infrequently exposed to the sun, especially the elderly, and postmenopausal women may need 800–1000 IU daily. From a review of available information, I conclude that people who get at least 700 IU of vitamin D daily and take calcium supplements have denser bones, have better muscle strength, and are likely to suffer fewer falls and fractures than those who don’t. The only caution is to avoid exceeding the government’s safe daily upper limit of 2,000 IU.
Glucosamine/Chondroitin: This supplement is widely used in the effort to help repair cartilage and relieve suffering from degenerative joint disease (osteoarthritis). After many conflicting studies, however, a recent, more definite large study showed that glucosamine was unable to relieve knee pain or cartilage loss in people with osteoarthritis. Although generally safe, this product would pose some risk to some people with shellfish allergies.
SOME SUPPLEMENTS DEFINITELY TO AVOID
Unless there is compelling evidence of efficacy—which is seldom the case—all supplements should be avoided. Three especially egregious products linked to serious dangers are the following: 1) Kava, which is taken to relieve stress and anxiety, is capable of producing serious liver disease, 2) Yohimbe (yohimbine hydrochroride), used to treat erectile dysfunction, is risky because the impure ingredient present in over-the counter preparations, can cause unpredictable effects on blood pressure, rapid heart rate, and other problems,.and 3) Aconite, touted to relieve inflammation and joint pain, can cause nausea, vomiting, low blood pressure, respiratory system paralysis, heart-rhythm disorders, and even death.
IS ANYTHING WORTH TAKING?
In general, normal diets contain more that enough to preclude the need for supplementation. If one has a demonstrated deficiency of any, then, upon the advice of a physician, supplementation may be justified. As noted above in the case of vitamin B12, folic acid, and Vitamin D, supplementation can be useful.