Vitamin and mineral supplements are important to maintaining proper levels of these nutrients when they aren’t obtained from the diet. Generally, if a human consumes a diet of broad based foods, there is little need for supplementation, unless they are afflicted with a chronic medical disorder which requires additional nutrients.
Vitamins and minerals do not have an impact on the immune system. Numerous articles have been published in peer-reviewed journals that have found very little evidence that supplements can lower risk of heart disease or one of the over 200 forms of cancer. What we need next, in the hierarchy of scientific evidence, is a systematic review published in an important journal.
And we got one.
A recent systematic review, published in the Annals of Internal Medicine, one of the top medical journals, found no consistently positive evidence that vitamin supplements had an effect on the reduction of the rates heart disease or cancer risk in the general population. The researchers observed that two trials found a small, borderline-clinically significant benefit from multivitamin supplements on cancer in men only and no effect on cardiovascular disease. However, because the results were so small, and no effects were observed in women, the authors strongly cautioned against overgeneralizing these results.
The review specifically covered only those studies that involved several kinds of vitamins, including multivitamins, vitamins A, C, D and E, calcium, iron, magnesium, folic acid and beta-carotene. As mentioned above, only one study found a slightly lower cancer risk for men who had been taking multivitamins for 10 years. Another study, which included both men and women, only found a slightly lower cancer risk for males. However, the risks reductions were small, and if they looked only at one type of cancer, the change in numbers was so small as to be meaningless. The review also found that these supplements had no effect on fatal and non-fatal heart disease-related events.
The authors also looked at individual micronutrients. Beta-carotene, which can be found naturally in foods like sweet potatoes, pumpkins and carrots, and vitamin E were not found to have any effects on cancer or cardiovascular disease risk. Furthermore, most of the studies involving vitamin D showed no effect on disease or death. An increased risk for hip fractures was found, however, for participants who took vitamin A in two of the studies.
It’s important to note that the authors admitted that their study only focused on primary prevention in generally healthy adults. It is possible, though evidence is lacking, that these vitamins may have a more beneficial clinical effect for adults who have been diagnosed for cancer or cardiovascular disease.
However, these researchers concluded that, for healthy individuals, current research establishes that vitamins may not have an effect on cancer or heart disease risk.
So don’t waste money on those supplements, unless you have a chronic condition where a physician recommends supplementation. Or if you have a strange diet where you are missing a key nutrient.
- Fortmann SP, Burda BU, Senger CA, Lin JS, Whitlock EP. Vitamin and Mineral Supplements in the Primary Prevention of Cardiovascular Disease and Cancer: An Updated Systematic Evidence Review for the U.S. Preventive Services Task Force. Ann Intern Med. 2013 Nov 12. doi: 10.7326/0003-4819-159-12-201312170-00729. [Epub ahead of print] PubMed PMID: 24217421. Impact factor=14.0.