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Why Take a Multivitamin; What to Take; What Not to Take

May 31, 2017 by Joel Fuhrman, MD

The 5 Vital Ingredients You Need in a Multivitamin, from B12 to Zinc

Of course, a healthful diet based on nutrient dense, 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 typically there are some nutrients that are lacking and these deficiencies can undermine your health.

Lacking some vitamins is a risk factor for chronic diseases and is common in the general population, especially in older people.1In contrast, the right amounts of vitamins and minerals has the potential to extend lifespan. Recent research concluded multivitamin use is associated with longer telomere length, which is an indicator of a slower rate of aging.2

We cannot be sure that we are getting the precise optimal amounts of vitamins and minerals every day from our diet, 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.

Be sure to supplement wisely. Below are the most common vitamin deficiencies:

Vitamin B12

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.3Insufficient 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 much 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 percent 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

Vitamin D

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

Vitamin K2

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 percent of the daily requirement for iodine was commonly met on a vegetarian or vegan diet.13  Another study concluded that 80 percent of vegans, 25 percent of vegetarians, and 9 percent 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 in 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 percent higher than the U.S. RDI.16-18

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

While most people can certainly benefit from a multivitamin, it is important to choose the right one. Just as it is important to avoid vitamin and mineral deficiencies, it is equally as important to avoid consuming excessively high levels of certain nutrients, and to steer clear of certain nutrients in supplement form.

Don’t take multivitamins containing folic acid, vitamin A and beta carotene.

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, and 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.

  1. Fletcher RH. Fairfield KM. Vitamins for Chronic Disease Prevention in Adults: Clinical Applications; JAMA; 2002; 287(3127-129.
  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/]
  4.  Hooshmand B, Solomon A, Kareholt I, et al: Homocysteine and holotranscobalamin and the risk of Alzheimer disease: a longitudinal study. Neurology 2010;75:1408-1414.
  5.  Allen LH: How common is vitamin B-12 deficiency? Am J Clin Nutr 2009;89:693S-696S.
  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.
  7.  Hyppönen E. Vitamin D and increasing incidence of type 1 diabetes-evidence for an association? Diabetes Obes Metab. 2010 Sep;12(9):737-43.
  8.  Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr 2004;80:1678S-1688S.
     Holick MF, Chen TC. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr 2008;87:1080S-1086S
  9. Tripkovic L, Lambert H, Hart K, et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr 2012.
  10.  Vitamin K2. Monograph. Altern Med Rev 2009;14:284-293.
  11. Gast GC, de Roos NM, Sluijs I, et al. A high menaquinone intake reduces the incidence of coronary heart disease. Nutrition, metabolism, and cardiovascular diseases : NMCD 2009;19:504-510.
    Beulens JW, Bots ML, Atsma F, et al. High dietary menaquinone intake is associated with reduced coronary calcification. Atherosclerosis 2009;203:489-493.
    Geleijnse JM, Vermeer C, Grobbee DE, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. J Nutr 2004;134:3100-3105.
  12. Oregon State University. Linus Pauling Institute. Micronutrient Information Center: Vitamin K [http://lpi.oregonstate.edu/infocenter/vitamins/vitaminK/]
  13. Waldmann A, Koschizke JW, Leitzmann C, Hahn A. Dietary intakes and lifestyle factors of a vegan population in Germany: results from the German Vegan Study. European Journal of Clinical Nutrition (2003) 57, 947–955.
  14. Krajcovicová-Kudlácková M, Bucková K, Klimes I, Seboková E.. Iodine deficiency in vegetarians and vegans. Ann Nutr Metab. 2003;47(5):183-5.
  15.  Hunt JR. Bioavailability of iron, zinc, and other trace minerals from vegetarian diets. Am J Clin Nutr 2003;78(suppl):633S–9S.
  16.  de Bortoli MC, Cozzolino SM. Zinc and selenium nutritional status in vegetarians. Biol Trace Elem Res. 2009 Mar;127(3):228-33. Epub 2008 Oct 25.
  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
  21. Bjelakovic G, Nikolova D, Gluud LL, et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev 2008:CD007176.
    Mayne ST. Beta-carotene, carotenoids, and disease prevention in humans. FASEB J 1996;10:690-701.


Joel Fuhrman, M.D. is a board-certified family physician, seven-time New York Times bestselling author and internationally recognized expert on nutrition and natural healing, who specializes in preventing and reversing disease through nutritional methods. Dr. Fuhrman coined the term “Nutritarian” to describe his longevity-promoting, nutrient dense, plant-rich eating style.
For over 25 years, Dr. Fuhrman has shown that it is possible to achieve sustainable weight loss and reverse heart disease, diabetes and many other illnesses using smart nutrition. In his medical practice, and through his books and PBS television specials, he continues to bring this life-saving message to hundreds of thousands of people around the world.