It is important to supplement wisely. During my 25 years in medical practice, I have seen thousands of people with common nutrient deficiencies creating health problems. Combining the right foods with the conservative and intelligent use of supplements was imperative for health recovery and even life saving. However, rather than boosting health, certain multivitamins may be harmful. And because of this, most studies do not show a consistent benefit of taking multivitamin/mineral supplements for preventing chronic diseases.1 A 2006 National Institutes of Health (NIH) State-of-the-Science Conference Statement reported on multivitamin/mineral supplements and chronic disease prevention studies. Their conclusion was: “Most of the studies we examined do not provide strong evidence for beneficial health-related effects of supplement.2
Since micronutrient deficiency is detrimental to your health, picking the right multivitamins is very important. The big question is why have most studies shown no benefit for preventing chronic disease? One important reason is that most multivitamin/mineral supplements on the market contain ingredients that have been shown by studies to be harmful in supplement form.
The following nutrients are beneficial when provided by whole foods, but may be harmful in supplement form
- Folic Acid. The synthetic folic acid found in supplements is chemically different from food folate, which is abundant in green vegetables, beans and other plant foods. Folate is especially important for women of childbearing age, to prevent against birth defects. However, women who take synthetic folic acid in multivitamins may be at increased risk of breast cancer.3-8 Folic acid supplementation also raises the risk of prostate and colorectal cancers.9-11Luckily, we don’t need to get folic acid from vitamins because folate is plentiful in green vegetables and other whole plant foods. Folate in its natural form protects against breast and prostate cancers.9,12-14 Of course when we get our folate from food it comes naturally packaged in balance with hundreds of other cancer protective micronutrients. Consuming folate-rich foods, not folic acid, during pregnancy may also offer protection against cardiac birth defects, childhood respiratory illnesses, and childhood cancers.15-21
- Vitamin A and Beta-carotene. Ingesting vitamin A or beta-carotene from supplements can potentially increase cancer risk by interfering with the absorption of other carotenoids with anti-cancer properties, like lutein and lycopene.22 Beta-carotene is a member of the carotenoid family, which are highly pigmented (red, orange, yellow), fat-soluble compounds naturally present in many fruits, grains, oils, and vegetables. Beta-carotene supplements are poor substitutes for the broad assortment of carotenoid compounds found in plants. Since beta-carotene gets converted into vitamin A by the body, there is no reason a person eating a reasonably healthy diet should require any extra vitamin A. There is solid research revealing that supplemental vitamin A induces calcium loss in the urine, contributing to osteoporosis.23 Too much vitamin A from supplements during pregnancy is associated with cardiac birth defects.24 On top of these risks, a recent meta-analysis found an increased risk of mortality in people who took supplemental vitamin A, beta-carotene, or vitamin E.25
- Vitamin E. As mentioned above, supplemental vitamin E in the dosage ranges higher than what can be achieved with food is associated with an increase in mortality risk. Vitamin E is an antioxidant vitamin that we can easily get from raw nuts and seeds, rather than in a supplement.25
- Selenium. There is evidence that high selenium levels are linked to diabetes, high triglycerides, prostate cancer, cardiovascular disease, and impaired immune and thyroid function. A healthy nutritarian diet contains adequate selenium, so selenium supplementation is not advised. For people eating a conventional diet with plenty of processed foods, studies have shown that selenium supplementation may have some protective effects, however these studies also show more detrimental effects as the dose gets higher. There is also a link between selenium excess and amyotrophic lateral sclerosis (ALS).26-29 The answer here is to have selenium sufficiency, but be careful not to get excess.
- Iron and copper. Iron and copper serve vital biological functions, but as we age excess amounts of these metals may build up and become toxic. The most common culprits of iron and copper excess are red meat and multivitamins. Iron is crucial for oxygen transport, and both iron and copper are essential for the proper function of several chemical reactions in several of the body’s cells and tissues. The human body evolved to store excess iron and copper to fuel these reactions in case of extreme conditions like bleeding or famine. However, their accumulation over time may be detrimental because both metals are involved in generating oxidative stress, a byproduct of energy production, which contributes to chronic diseases—specifically cardiovascular disease and brain disorders like Alzheimer’s disease. There are appropriate times to supplement with iron such as when there is a deficiency or an increased biological need, as in pregnancy.
It is important to keep in mind that supplementation is individual and in most cases necessary to ensure adequate nutrients; the bottom line is to supplement wisely.