JustTheScience

A study by Garland et al (2005) demonstrated that it is difficult for adults in America to get consistently adequate levels of micronutrients, especially those that come from more unconventional sources (i.e. Vitamin D, which comes from sunlight).¹  Several studies have determined specific demographics that are particularly susceptible to micronutrient deficiencies, including:  women of child bearing age who may become pregnant  (Olshan et al 2002),² people with deficiency inducing diseases such as type 2 diabetes (Barringer et al 2003),³ 40% of people over age 65  (Chandra 2001),⁴ 50% of postmenopausal women (Holick et al 2005), ⁵ and 100% of adolescents (Stang et al (2000)⁶.  A common dietary supplement for these demographics, and those concerned about their daily intake of essential micronutrients are multivitamins.  Extensive research has been conducted on the validity of this practice, with a major concern being whether multivitamins are as effective in delivering their content as natural sources.  Earnest et al (2003) found that intake of multivitamins did in fact increase overall vitamin levels by studying the levels of vitamins B6, B12, and folic acid over the course of 24 week period and a study by Navarro et al (2003) found that the multivitamin disintegration properties due to physical make up (whole tablet, crushed tablet, powder) did not affect the delivery efficacy of micronutrients, and that multivitamins are an effective mechanism of micronutrient delivery. ^7 8

Numerous studies have found correlations between taking daily multivitamins and a number of health benefits. These include: increased cognitive functions in the elderly (Chandra 2001), ⁹ lower instances of colorectal cancer (Jacobs et al 2003),¹⁰ lower instances of heart disease (Holmquist et al 2003), ¹¹ improved immune system in people over 59 years of age (Bogden et al 1994), ¹² and increased in bone density in postmenopausal women (Morton et al 2001).¹³  Separate studies have determined multivitamin intake during pregnancy decreased levels of childhood cancers (Olshan et al 2002) ¹⁴, lowers instances of birth defects (Botto et al 2004),¹⁵ and lowers instances of childhood anemia (Geltman et al 2004).¹⁶

It is important to note that excess ingestion of all vitamins is not beneficial.  In some instances, vitamin intake above a certain level will have no effect.  For example, Levin et al (1996) found that doses of Vitamin C over 400 mg per day had no physiological effect, and any amount over 1,000 mg is simply excreted not utilized.¹⁷  In other instances, overdosage can be detrimental.  A study by Graat et al (2002) found that taking Vitamin E in supplement form worsens acute respiratory tract infections in well nourished people over the age of 60,¹⁸ and Omenn et al (1996) found correlations between taking Vitamin A in supplement form and increased lung cancer rates and cardiovascular disease in smokers.¹⁹  Wooltorton (2003) examined micronutrient overdosage effects that exist for all individuals, and found: overdosage of magnesium and phosphorus can cause diarrhea;  overdosage of iron can cause constipation, nausea, vomiting, and reduced zinc uptake; overdosage of zinc can cause nausea, vomiting, immunosuppression, and impaired copper uptake; and overdsoage of selenium can cause brittle hair and nails, peripheral neuropathies, and gastrointestinal upset.²⁰  A study by Lawson et al (2007) found that high doses of multivitamins correlates with increased levels of advanced and fatal prostate cancer.²¹

Based on these studies, it is reasonable to state that multivitamins are a beneficial supplement to one’s daily diet, provided that a recommended dosage is taken. If one feels they are in a demographic that could be affected negatively by this supplementation, contact a physician before starting.

1. Do sunlight and vitamin D reduce the likelihood of colon cancer? [↩]
2. Maternal Vitamin Use and Reduced Risk of Neuroblastoma [↩]
3. Effect of a Multivitamin and Mineral Supplement on Infection and Quality of Life [↩]
4. Effect of Vitamin and Trace-Element Supplementation on Cognitive Function in Elderly Subjects [↩]
5. Prevalence of Vitamin D Inadequacy among Postmenopausal North American Women Receiving Osteoporosis Therapy [↩]
6. Relationships between vitamin and mineral supplement use dietary intake and dietary adequacy among adolescents [↩]
7. Plasma Changes in Micronutrients Following a Multivitamin and Mineral Supplement in Healthy Adults [↩]
8. Efficacy of a complex multivitamin supplement [↩]
9. Effect of Vitamin and Trace-Element Supplementation on Cognitive Function in Elderly Subjects [↩]
10. Multivitamin Use and Colorectal Cancer Incidence in a US Cohort: Does Timing Matter? [↩]
11. Multivitamin Supplements Are Inversely Associated with Risk of Myocardial Infarction in Men and Women [↩]
12. Daily micronutrient supplements enhance delayed-hypersensitivity skin test responses in older people [↩]
13. Vitamin C Supplement Use and Bone Mineral Density in Postmenopausal Women [↩]
14. Maternal Vitamin Use and Reduced Risk of Neuroblastoma [↩]
15. Vitamin Supplements and the Risk for Congenital Anomalies Other Than Neural Tube Defects [↩]
16. Daily Multivitamins With Iron to Prevent Anemia in High-Risk Infants: A Randomized Clinical Trial [↩]
17. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance [↩]
18. Effect of Daily Vitamin E and Multivitamin-Mineral Supplementation on Acute Respiratory Tract Infections in Elderly Persons [↩]
19. Effects of a Combination of Beta Carotene and Vitamin A on Lung Cancer and Cardiovascular Disease [↩]
20. Too much of a good thing? Toxic effects of vitamin and mineral supplements [↩]
21. Multivitamin Use and Risk of Prostate Cancer in the National Institutes of Health–AARP Diet and Health Study [↩]