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Suzanne P. Murphy, Kami K. White, Song‐Yi Park | American Journal of Clinical Nutrition | (2007)
Primary Link Pubmed DOI Openalex Full text (OA)

Key Takeaways

Sample Definition And Size

Participants were from the Hawaii–Los Angeles Multiethnic Cohort (MEC). At baseline (1993–1996), 21,056 multivitamin supplement users and 69,715 nonusers without chronic diseases were included. Additionally, 26,735 MEC participants in Hawaii (1999–2001) reported using 1,246 different multivitamin products.

Study Type

Observational cohort study using self-administered quantitative food-frequency questionnaires and open-ended supplement use reporting.

Conflicts Of Interest

No conflicts of interest are declared in the provided abstract.

Results Summary

From food only, nutrient adequacy prevalence was on average 2 percentage points higher in supplement users versus nonusers. Including supplements improved adequacy by an average of 8 percentage points for both men and women. Supplement users were more likely to have potentially excessive intakes, particularly for iron, zinc, vitamin A, and niacin. Among the 1,246 products reported, nutrient composition varied widely, with the 90th percentile containing up to 10-fold higher amounts than the median for some nutrients.

Abstract

Use of multivitamin-multimineral supplements is widespread and can contribute substantially to total nutrient intakes. In the Hawaii-Los Angeles Multiethnic Cohort (MEC), 48% of men and 56% of women without chronic diseases reported use of multivitamin supplements at least weekly over the past year. We calculated the prevalence of nutrient adequacy for 17 nutrients based on responses to a self-administered quantitative food-frequency questionnaire administered to MEC participants at baseline in 1993-1996. Although the prevalence of nutrient adequacy from food only was higher for multivitamin supplement users (n = 21,056) than for nonusers (n = 69,715), differences averaged only 2 percentage points. For multivitamin users, the prevalence of adequacy improved by an average of 8 percentage points for both men and women when intake from supplements was included. Users were also more likely to have potentially excessive intakes, particularly for iron, zinc, vitamin A, and niacin. The 26,735 MEC participants in Hawaii who answered an open-ended question about multivitamin use in 1999-2001 reported using 1246 different products. The nutrient profile of these products varied widely, and the composition of products at the 90th percentile was 10-fold greater than the composition at the median for some nutrients. We conclude that analyses of nutrient adequacy and excess for supplement users should be extended to national samples and that composition data on actual supplements used are preferable to assuming a default nutrient profile for multivitamin supplements. Multivitamin products could be better formulated to reduce the prevalence of inadequacy and also to reduce the risk of excessive intakes.

Referenced In

Lee Johnson
2 months ago
Health, Fitness, and Nutrition

Do Multivitamins Actually Work?

About one-third of all adults in the United States take a multivitamin/mineral supplement, and they’re popular around the world. It sounds like a no-brainer – the more vitamins and minerals, the better, right?

Well, that isn’t actually as clear as you might think.

Multivitamins Generally Improve Nutrient Intake (But Not Always)

It’s true that multivitamins will generally help when it comes to getting adequate nutrient intake. However, there are some key caveats to keep in mind.

Research does show that both men and women who consume multivitamins are significantly more likely to have adequate nutrient intake. But most adults – multivitamin-users or not – get enough nutrients from their diet.

They also make you more likely to get too much of certain nutrients, like vitamin A. This might not sound too bad, but excessive consumption also carries risks.

Multivitamins Don’t Reduce Mortality Overall

Generally speaking, studies looking at the effect of multivitamin use on all-cause mortality don’t find a difference.

For example, one meta-analysis of randomized controlled trials used a pooled sample of over 91,000 people, with an average age of 62. It didn’t find any difference in mortality risk between people who took multivitamins and those who didn’t. There was a trend towards reduced risk for primary prevention – for participants who didn’t already have a condition – but this didn’t reach significance.

Multivitamins Have Mixed Effects on Specific Conditions

Many studies on multivitamin supplementation look specifically at cardiovascular disease or cancer risk.

One systematic review combined the results of 84 studies with almost 740,000 participants in total and found “little or no benefit” in preventing cardiovascular disease, cancer and death. However, the study found a small benefit of multivitamin use on cancer.

The devil is in the details, though: the absolute risk reduction was 1.2% at most, some vitamins were useless (such as vitamins D and E) and others (beta carotene) actually increased lung cancer risk.  

Who Should Take Multivitamins?

The evidence suggests [1] that folic acid, iron, iodine and vitamin D are helpful during pregnancy, vitamin D-fortified milk is good for breastfeeding infants and that adults aged 50 or over should consider B12 supplementation. Other than this and specific deficiencies, there is little benefit to multivitamin use.

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