Multivitamins — safe but not beneficial; are we sure?

Many vitamins and minerals have been touted as potentially beneficial for a number of diseases — eg, vitamin E for cancer, selenium for diabetes. If you search long enough, you can find peer-reviewed published literature to support a beneficial effect, no effect and (less often) an adverse effect.

My e-mail yesterday morning contained two separate links to the same article from the investigators in the Women’s Health Initiative study, concluding that multivitamins had no effect on the incidence of either cancer or cardiovascular disease in the large cohort of ~160,000 women followed carefully for eight years.

I doubt that these findings will have any major impact on multivitamin use in the United States as it will be swamped by the millions of dollars spent on advertising “supplements” of all kinds. The claims in these ads are really quite amazing. Much of the advertising relates to adding healthy “nutrients” to the food chain in orange juice, yogurt, cereals, etc. I can’t think of any potential for harm in this.

More concerning, however, is the potential for harm when they are sold as stand-alone products — tablets or capsules. One of the major factors affecting the overall health of our patients with chronic conditions, such as heart disease and diabetes, is patient compliance with medication. Every additional medication we prescribe decreases the likelihood of any of them being taken. I have not done any formal survey, but when most of my patients come to their first clinic visit with a list of their medications, it is more common than not that the list contains at least one supplement — usually more than one.

To the best of my understanding, FDA-approved therapies are only effective if the patient takes them and in the manner prescribed. (There are still nursing homes that give the weekly oral bisphosphonate with apple sauce to minimize the potential for gastrointestinal symptoms while totally removing any potential benefit of the therapy.) By all means, do not discourage your patient from using vitamins and other nutritional supplements but to the extent possible, encourage them to incorporate them into their diet rather than as stand-alone products.

For more information:

J Natl Cancer Inst. 2009;101(1):14-23. PMID: 19116389.

Ann Intern Med. 2007;147(4):217-23. PMID: 17620655.

Arch Intern Med. 2009;169(3):294-304.