Kate Gibson, MS-4
Faculty Peer Reviewed
A 65 year old male patient with a history of hypertension and hyperlipidemia comes into the clinic for a regular visit. On his way out he asks, “Should I be taking a multivitamin?” You stop and think for a minute and decide, why not? But is there any actual evidence supporting the effectiveness of daily use of a multivitamin?
According to the National Health and Nutrition Examination Survey from 1999-2000, 35% of American adults report regular use of a multivitamin/multimineral product, with 52% reporting use of a multivitamin in the past month. It is estimated that adults in the US spend between $1.3 and $1.7 billion on multivitamins annually. This use increases when considering patients with cancer or a chronic disease, with up to 63% reporting the use of two or more dietary supplements.  While it is generally thought that multivitamins have a beneficial effect on immunologic factors, this has yet to be definitively shown.
To investigate this further, a study looking at the effect of multivitamin/mineral supplementation on infection and quality of life was published in 2003 in the Annals of Internal Medicine. The study was a randomized, double-blind trial that enrolled 130 patients, 45 years of age or older, who were assigned either a multivitamin or placebo for one year. The patients were also analyzed in groups by age and either the presence or absence of diabetes, with the primary endpoint being the incidence of participant-reported infection, determined by both a patient diary of illness and days of missed work due to illness. Quality of life was also investigated as a secondary endpoint. The results showed that 73% of the placebo group experienced one or more infection-related illnesses over the course of the year, compared to only 43% in the treatment group. Likewise, the placebo group reported 57% absenteeism due to illness, compared to only 21% reported in the treatment group. Upon further inspection, however, it became clear that the difference in the results between the two groups was primarily due to patients with diabetes: 93% of diabetics in the placebo group reported an infectious illness, compared to only 17% of diabetics in the treatment group. When data from the patients with diabetes were removed and the data were re-analyzed, the two treatment groups were almost identical in rate of infections and absenteeism. Also, there was no difference in quality of life between the two groups, nor was a difference noted when the groups were separated by age. While this study failed to show a benefit of multivitamin use in the general population, it did demonstrate a clear reduction in participant-reported infection in subjects with diabetes. 
Another study published in the British Medical Journal in 2005 investigated a similar question, but focused on an older population. The study enrolled 910 women and men living in the community, aged 65 years or older, into a randomized controlled trial in Scotland where participants were given either a multivitamin/multimineral supplement or placebo for one year. Primary outcome measures were number of contacts with primary care physicians due to illness, self-reported infection, and quality of life. The results of this study showed no statistically significant change between the treatment and placebo groups with regard to any of the primary outcomes. Likewise, no difference was seen in secondary outcomes, which included the number of antibiotic prescriptions written and number of hospital admissions. Of note, the participants were older patients living in the community and as such were likely healthier than patients living in nursing homes or assisted-living facilities.
A controversial study published by the American Journal of Epidemiology in 1996 also evaluated multivitamin and mineral supplementation, but in a population of over 3000 people living in rural China. This study showed a non-significant reduction in overall mortality (relative risk 0.93, 95% confidence interval 0.75-1.16) in the supplement group compared to a placebo group, with a more pronounced (but non-significant) effect on cardiovascular deaths (relative risk 0.63, 95% confidence interval 0.37-1.07). There was also less elevation in both systolic and diastolic blood pressure values in the treatment group. However, the applicability of this study to the American population has been widely criticized, given the vast difference in nutritional status between the American population and people living in rural China.
In addition to assessing the effectiveness of multivitamin use on illness prevention, there have been many studies looking at the effects on specific diseases. An investigation into the effect of multivitamin supplementation on cognitive function found a mild beneficial effect on verbal fluency in patients over 75 years of age and in those patients considered to be at increased risk of micronutrient deficiency. However, no cognitive benefit was seen in patients 65 years or older living in the community setting.
Bone Quality/Fracture Risk
Bone quality and rate of falls in patients living in residential care settings have also been investigated. One study found that patients assigned to take a multivitamin had elevated serum B12, folate, and 25(OH)D levels, and subsequently had an improvement in bone quality (not statistically significant) and a reduction in falls, both of which could result in an overall decrease in the number of fractures.
In September 2006, the NIH explored the use of daily multivitamin/mineral supplements for the prevention of cancer and chronic disease by performing a review of randomized clinical trials. From this review they were able to conclude that “the strength of evidence is insufficient to support the presence or absence of a benefit from routine use of multivitamin and mineral supplements by adults in the United States for primary prevention of cancer, cardiovascular disease, hypertension, cataracts, or age-related macular degeneration.” The review also looked at possible adverse effects of multivitamin and mineral use and concluded that overall “no consistent pattern of increased adverse events was evident.”
Interestingly, the US Congress recommended in 2006 that the Older Americans Act Nutrition Program, which provides the “meals on wheels” service and “senior dining”, consider providing multivitamin/mineral supplements in addition to meals. The OAANP challenged this stance, stating that multivitamins are not a quick fix for poor diets, have unproven benefit and safety, have a risk of nutrient-drug interactions and toxicity, and would cut into their limited funds.
The use of multivitamins to improve health has been a subject of continued debate for some time. After reviewing the most recent literature, it appears there is little evidence to support the claim that daily multivitamin use in the general population has a positive impact on health. However, certain populations, such as the undernourished or those who have diabetes, do appear to derive some benefit from the use of multivitamins. Overall, more studies are needed to continue investigating this important question. One study, the Physicians’ Health Study-II, hopes to provide some answers by looking at multivitamin use and its prevention of cardiovascular disease and cancer, among other illnesses, in over 14,000 men. Concluded in late 2007, it is hoped that the results from this study will further elucidate the possible relationship between daily multivitamin use and improved health.
Reviewed by Michelle McMacken, MD, Assistant Professor of Medicine
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