Multivitamins, single vitamins, and minerals continue to demonstrate high usage and consumer confidence among Americans who take supplements, according to CRN’s 2015 Consumer Survey on Dietary Supplements. The multivitamin in particular is the most popular with supplement users, followed by vitamin D and vitamin C.
Building on this good news is the USDA and the U.S. Department of Health and Human Services’ recent release of the 2015–2020 Dietary Guidelines for Americans, which recognizes dietary supplements as “useful in providing one or more nutrients that otherwise may be consumed in less than recommended amounts or that are of particular concern for specific population groups.” Furthermore, the guidelines identify vitamins A, D, E, and C as nutrients that are “consumed by many individuals in amounts below the estimated average requirement or adequate intake levels.”
So, while the continued popularity of and general consumer and government trust in multivitamins and single vitamins remain strong, one question remains: What, exactly, are all of the specific benefits of vitamin supplementation to human health?
Researchers are actively working to answer this question, and they are looking at elements of wellness ranging from cardiovascular health to cancer prevention to cognitive performance. Ahead, we look at notable as well as recent multivitamin/vitamin studies and the conclusions reached by their researchers.
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Multivitamins and Cancer
Study Title: Multivitamins in the Prevention of Cancer in Men: The Physicians’ Health Study II Randomized Controlled Trial
This large-scale, randomized, double-blind, placebo-controlled trial began in 1997 and ended 14 years later, in 2011. It sought to determine whether long-term multivitamin supplementation decreases the risk of total and site-specific cancers in men.
The study included more than 14,000 subjects (all U.S. physicians, all male) aged 50 and older. Intervention was a daily multivitamin or a placebo. The conclusion reached was that daily multivitamin supplementation modestly but significantly reduced the risk of total cancer.
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Vitamin D Status: African-American, Hispanic Subjects
Study Title: Vitamin D Status and Rates of Cognitive Decline in a Multiethnic Cohort of Older Adults
The authors of this 382-subject, eight-year, observational study, published in 2015 in JAMA Neurology, concluded that low vitamin-D levels were associated with accelerated decline in cognitive function in ethnically diverse older adults (75 years at the start of the study). These adults included African-American and Hispanic persons exhibiting a high prevalence of vitamin D insufficiency or deficiency, and individuals with normal cognitive function, mild cognitive impairment, and outright dementia.
The researchers found that study participants with insufficient or deficient vitamin D levels experienced cognitive decline in two areas—short-term memory and executive function—at a rate about 2.5 times faster than participants with adequate vitamin D levels. It remains to be determined whether vitamin D supplementation slows cognitive decline.
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Prenatal Vitamin/Mineral Supplementation
Study Title: The Association between Third-Trimester Multivitamin/Mineral Supplements and Gestational Length in Uncomplicated Pregnancies
A 427-person study published online in August 2015 and in print in the Australian Women and Birth journal in February of this year sought to retrospectively analyze the relationship between third-trimester maternal micronutrient supplementation and gestation length of the newborn baby at birth in uncomplicated pregnancies in Gold Coast and Logan Hospitals in South East Queensland.
The findings were that women in their third trimester taking zinc, folic acid, or iron supplements in combination with a multivitamin were twice as likely to give birth beyond 41 completed weeks than those who did not take any supplement. Those not taking such supplements were found to experience a lower rate of post-date labor and require induced labor. The conclusion reached by the authors was that length of gestation demonstrates significant associations with micronutrient supplementation practices.
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Multivitamins and Stroke Mortality
Study Title: Multivitamin Use and Risk of Stroke Mortality: the Japan Collaborative Cohort Study
A follow-up study published in 2015 in the journal Stroke of 72,180 Japanese men and women free from cardiovascular diseases and cancers between 1988 and 1990 monitored the participants until December 31, 2009, to examine the association between multivitamin use and risk of death from stroke and its subtypes.
Lifestyle choices, including multivitamin use, were collected via self-administered questionnaires. During a median follow-up of roughly 19 years, the researchers identified 2087 deaths from stroke, including 1148 ischemic strokes and 877 hemorrhagic strokes. After adjustment for potential confounders, multivitamin use was associated with lower (but borderline) significant risk of death from total stroke but not hemorrhagic stroke.
An additional conclusion reached by the researchers was that regular, frequent multivitamin intake was associated with reduced risk of total and ischemic stroke mortality among Japanese people with low consumption of fruits and vegetables.
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Multivitamins, Minerals, and CVD
Study Title: Multivitamin-Mineral Use Is Associated with Reduced Risk of Cardiovascular Disease Mortality among Women in the United States
The purpose of this study was to examine the association between multivitamin (MV) use and cardiovascular disease–specific death among American adults without cardiovascular disease (CVD). A nationally representative sample of adults from the Centers for Disease Control’s National Health and Nutrition Examination Survey data (NHANES III, 1988–1994; 8678 participants aged 40 years or older) was matched with mortality data reported by the National Death Index through 2011 to examine associations between multivitamin with minerals (MVM) use, MV use, and CVD mortality, adjusting for multiple potential confounders.
The researchers observed no significant association between CVD mortality and those taking multivitamins (with or without mineral ingredients) compared with those not taking them; however, when those taking the supplements were classified by the reported length of time the products were regularly taken, a significant association was found with MVM use of greater than three years (compared with nonusers) and reduced CVD mortality risk for women when models controlled for age, race, education, body-mass index, alcohol use, aspirin use, serum lipids, blood pressure, and blood glucose/glycated hemoglobin. This finding applied to women only. The study was published in 2015 in the Journal of Nutrition.
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