If I eat a healthy diet, do I really need a multivitamin?
Maintaining adequate levels of essential vitamins and minerals is crucial for good health. Suboptimal intake of some vitamins is a risk factor for chronic diseases and common in the general population, especially the elderly.1 In contrast, micronutrient adequacy has the potential to extend lifespan – recent research has found that multivitamin use is associated with longer telomere length, which is an indicator of a slower rate of aging.2
Of course, a healthful diet based on whole plant foods is our best protection against chronic disease. In addition to vitamins and minerals, a diet of colorful natural plant foods provides us with thousands of beneficial phytochemicals. But there are some nutrients that are lacking even in an ideal diet, and deficiencies can undermine your health. Also, we cannot be sure that we are getting the precise optimal amounts of vitamins and minerals every day from our diet – especially since absorption efficiency and utilization of nutrients varies from person to person. A high quality multivitamin can fill these gaps, ensuring that we get adequate amounts of essential micronutrients.
Certain vitamins and minerals are often lacking even in a healthy diet:
Vitamin B12 is required for important biological functions like red blood cell production, nervous system function, and DNA synthesis. Deficiency in B12 can cause a variety of health problems including elevated homocysteine (a cardiovascular risk factor), anemia, depression, confusion, fatigue, digestive issues, and nerve damage.3 Insufficient B12 levels are also associated with increased risk of Alzheimer’s disease.4
Vitamin B12 is unique in that it is made only by microorganisms. Because our produce is washed and often transported far before we eat it (soil contains B12-producing microorganisms), most of us are unable to get sufficient B12 from plant foods alone. B12 deficiency is common, especially in vegans who don’t supplement and in the elderly – our ability to absorb B12 decreases with age, and about 20% of adults over the age of 60 are either insufficient or deficient in vitamin B12.5 Supplementation with vitamin B12 is likely important for most people, and absolutely required for most vegans to achieve sufficient B12 levels.6
Once thought to be important only for bone health, scientists have now found that Vitamin D has important actions in almost every cell in the human body.7 Consequently, insufficient vitamin D levels are associated with several cancers, diabetes, cardiovascular disease, depression, and autoimmune diseases. Insufficient vitamin D levels are also very common.8 Since many of us live in cool climates and work indoors, and because of the potential risks of skin damage and skin cancer, supplementing is the best choice for achieving adequate vitamin D levels. In my experience, 2000 IU has been an appropriate dose to bring most people into the favorable blood 25(OH)D range of 30-50 ng/ml (I also recommend getting a blood test to confirm adequate levels). For extra assurance, I’ve also utilized Vitamin D3 because of its high biological value, the most effective form for raising 25(OH)D levels.9
There are two forms of vitamin K, K1 and K2. Vitamin K2 seems to be more important to supplement – vitamin K1 is abundant in leafy green vegetables, so those on a healthful diet would not need to supplement with K1; vitamin K2 is produced by microorganisms and is low in plant foods. Also, vitamin K2 supplementation may offer additional health benefits: Vitamin K2 supplementation has been shown to reduce the risk of fracture, reduce bone loss, and increase bone mineral density in women with osteoporosis.10 In several studies, vitamin K2 intake was associated with reduced risk of heart disease or coronary artery calcification (an indicator of increased cardiovascular risk), whereas no such association was found for K1.11 The human body can synthesize some K2 from K1, and intestinal bacteria can produce some usable K2, but these are very small amounts.12 Therefore, it is likely important to supplement with K2.
Iodine is required by the body to make thyroid hormones. A recent study of vegans estimated that only about 40% of the daily requirement for iodine was commonly met on a vegetarian or vegan diet.13 Another study concluded that 80% of vegans, 25% of vegetarians, and 9% of conventional eaters are iodine-deficient.14 Most plant foods are low in iodine due to soil depletion. Kelp, a sea vegetable, is a good source of iodine, but is not commonly eaten on a regular basis and may actually provide excessive amounts of iodine. The chief source of iodine in the typical American diet is iodized salt. Since salt should be avoided for good health, it is important to supplement with iodine to maintain adequacy.
Zinc is essential for immune function, growth, and reproduction, and supports hundreds of chemical reactions. Zinc is abundant whole plant foods, but is not readily absorbed. Beans, whole grains, nuts, and seeds contain zinc, but also contain substances that inhibit zinc absorption.15 A recent study of vegetarians found a high prevalence of zinc deficiency, and zinc requirements for those on a completely plant-based diet are estimated to be about 50% higher than the U.S. RDI.16,17,18 Zinc is especially important for men, because it is concentrated in the prostate and promotes death of cancer cells, possibly by suppressing the activity of inflammatory molecules. Long-term zinc supplementation is associated with reduced risk of advanced prostate cancer.19
Multivitamins must be chosen wisely
While most people can certainly benefit from a multivitamin, it is important to choose the right one. It is important to avoid vitamin and mineral deficiencies, but it is just as important to avoid consuming excessively high levels of certain nutrients, and to steer clear of certain nutrients in supplement form. The synthetic folic acid in supplements is not the same as natural folate, found in high concentrations in green vegetables; taking supplemental folic acid may increase the risk of breast, prostate, and colorectal cancers.20 Vitamin A and beta-carotene in supplement form have also been shown to increase the risk of cancers, possibly by interfering with the absorption of other carotenoids, and supplemental vitamin A, beta-carotene, or vitamin E are all associated with increased risk of death.21 These shocking scientific findings mean that most conventional multivitamins act as a double-edged sword, containing both helpful and harmful elements.
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2. Xu Q, Parks CG, DeRoo LA, et al. Multivitamin use and telomere length in women. Am J Clin Nutr. 2009 Jun;89(6):1857-63.
3. Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Vitamin B12 [http://ods.od.nih.gov/factsheets/VitaminB12/]
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6. Bor MV, von Castel-Roberts KM, Kauwell GP, et al: Daily intake of 4 to 7 microg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12-related biomarkers in a healthy young population. Am J Clin Nutr 2010;91:571-577.
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12. Oregon State University. Linus Pauling Institute. Micronutrient Information Center: Vitamin K [http://lpi.oregonstate.edu/infocenter/vitamins/vitaminK/]
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17. Frassinetti S, Bronzetti G, Caltavuturo L, et al. The role of zinc in life: a review. J Environ Pathol Toxicol Oncol. 2006;25(3):597-610.
18. Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Zinc. [http://ods.od.nih.gov/factsheets/Zinc/]
19. Gonzalez A, Peters U, Lampe JW, White E. Zinc intake from supplements and diet and prostate cancer. Nutr Cancer. 2009;61(2):206-15
20. Charles D, Ness AR, Campbell D, et al. Taking folate in pregnancy and risk of maternal breast cancer. BMJ 2004;329:1375-1376.
Figueiredo JC, Grau MV, Haile RW, et al. Folic acid and risk of prostate cancer: results from a randomized clinical trial. J Natl Cancer Inst 2009;101:432-435.
Fife J, Raniga S, Hider PN, et al. Folic Acid Supplementation and Colorectal Cancer Risk; A Meta-analysis. Colorectal Dis 2009.
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