Multivitamin: Good, bad or equivocal?

Multivitamins are one of the most commonly consumed supplements in the United States, taken by at least one-third of the population (J Nutr. 2011;141(2):261-266). We are bombarded by vitamin advertising. Yet we hear so much conflicting information about them from physicians and marketers. Are they beneficial or are they detrimental? At least with multivitamins, I will attempt to address these questions with several studies.

The quick and dirty answer is that it appears to depend on the demographics utilizing them and also the content of the multivitamins themselves. So the real question becomes, who should and who should not be taking them? There are studies that have been done on men and women looking at mortality risk and chronic diseases, such as cancer and age-related macular degeneration.

Cancer benefit in men

The Physicians’ Health Study II is the only well-designed, randomized, double-blinded, placebo-controlled trial (RCT), the gold standard of studies, to date that looks at multivitamins. This study was published in JAMA and indicates that multivitamins may be beneficial for men to prevent the overall risk of cancer (JAMA online Oct. 17, 2012). The results showed that men who took a daily multivitamin were 8 percent less likely to develop cancer overall compared to the placebo group. Even though this is a modest effect, the results were statistically significant.

For those who did have cancer, there was also a trend toward reduction in cancer mortality of 12 percent, but it did not reach the threshold of statistical significance. When they analyzed cancers individually, such as prostate and colorectal cancers, there was no difference with the placebo group. The duration of the study was considered substantially long at 11 years. The demographics included 14,641 healthy male U.S. physicians who were at least 50 years old. The multivitamin used in the study was Centrum Silver.

It may be well worth the effort for men over the age of 50 to take a multivitamin, since it is an easy way to reduce the risk of a broad category of chronic diseases, including cancer that is difficult to treat in many circumstances. The authors stressed that this should not replace a good diet and exercise, which are more likely to have larger beneficial effects on cancer.

Cancer effect for postmenopausal women

In the Women’s Health Initiative, a large observational study, there was neither an increase nor a decrease in the risk of cancer with multivitamins (Arch Intern Med. 2009(3);169:294-304). Does this mean that multivitamins don’t have the same effect in women? Not necessarily.

The design of each of the two studies was different. The previous study was a randomized controlled trial comparing a group of males who took a multivitamin to those who took a placebo, whereas this study was large, but observational — participants were observed over time — and thus is not as well designed. Therefore, the Physicians’ Health Study II had a better design and more definitive results. Interestingly, the authors of this study concluded that diet, with an emphasis on fruits and vegetables, and exercise are more beneficial than a multivitamin. This conclusion is a similar to the previous study.

Mortality effect for postmenopausal women

For postmenopausal women, taking a multivitamin may be detrimental. There was an increased risk of mortality of 6 percent in women taking a multivitamin which, though modest, is still statistically significant, according to the Iowa Women’s Health Study (Arch Intern Med. 2011;171(18):1625-1633).

However, according to this study, copper was found to have a 45 percent increased risk of mortality in postmenopausal women. I described this study in more detail in my Oct. 25, 2011 article.
So why do I mention this study? To emphasize the fact that, though this is a large observational study like the Women’s Health Initiative, it is not as well designed, nor are the results as definitive as a RCT like the Physician’s Health Study II mentioned above. For instance, I could not find details about the dose of copper nor whether one standard multivitamin was used.

Regardless, there needs to be a RCT to determine if multivitamins are harmful in postmenopausal women. What I might suggest is that postmenopausal women think twice about taking the multivitamin in the Physician’s Health Study II, since it contained copper. It is important to ask your doctor whether multivitamins are appropriate for you and, if so, which one.

Age-related macular degeneration (AMD) and multivitamins

A multivitamin was shown to be beneficial in preventing the progression of AMD to advanced stage disease. This was a well-designed RCT called the AREDS study (Arch Ophthalmol. 2001;119:1417-1436). The results showed a significant 28 percent reduction in risk of worsening disease in patients between the ages of 55 and 80 years old. The study’s duration was 6.3 years. The multivitamin used contained a combination of vitamin C (500 mg), vitamin E (400 IU), beta carotene (15 mg), zinc (80 mg) and copper (2 mg).

This multivitamin combination also prevented visual acuity loss by 27 percent. These results are impressive, since advanced AMD is the leading cause of central vision loss in patients 65 years and older (Arch Ophthalmol. 1998;116(5):653-658). The study’s conclusion suggests that patients with AMD take this multivitamin combination as long as they don’t have contraindications, such as smoking. Before starting this type of multivitamin, please consult an ophthalmologist.

To review or summarize, multivitamins in the right population have substantial risk reduction effects, such as in cancer with men. However, benefits may be dependent on the population, for with postmenopausal women, multivitamins may actually increase the risk of mortality. They may also depend on the multivitamin’s composition — not all multivitamins are created equal. For example, a certain combination of elements is beneficial for macular degeneration, not just any multivitamin. Thus, one size does not fit all. And remember, a supplement is just that, it should supplement a healthy diet.

Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management.  For further information, go to the website www.medicalcompassmd.com and/or consult your personal physician.