5 Key Nutrients Your Diet May Lack

Do you take a vitamin supplement every day? More than half of all Americans do, usually in the form of a multivitamin and mineral. But do you really know what you are ingesting in an effort to promote good health? When it comes to multivitamins, my advice is to proceed with caution.

Do You Even Need to Take a Multivitamin?

No supplement or multivitamin can take the place of a nutrient-dense, plant-rich diet with its fiber and full spectrum of both discovered and yet-to-be discovered nutrients.

However, taking a well-designed multivitamin and mineral supplement can be an important contributor to good health. That’s because very few people eat so healthfully that they get the ideal amount of every vitamin and mineral needed in optimal amounts. For example, iodine, zinc, vitamin B12, vitamin K2, and vitamin D3 are difficult to obtain in optimal levels through plant foods. Therefore, using a safe, well-designed multivitamin makes sense.

Why Can’t Diet Do it All?

Although the vast majority of our vitamins and minerals should come from foods, even a healthy, well-planned diet could be lacking in certain essential nutrients. Here are five key nutrients your body might not be getting from your healthful diet:

Vitamin B12

  • Made by microorganisms and not present in plant foods
  • Deficiency is more common in vegans and those ages 60 and older
  • Important in red blood cell production, nervous system function, DNA synthesis
  • Maintaining sufficient B12 levels may help to protect against Alzheimer’s disease
  •  B12 deficiency causes anemia, depression, confusion, fatigue, digestive issues, nerve damage


  • Vegans, vegetarians, and flexitarians tend to require more zinc because zinc from plant products is less readily absorbed
  • Important in immune function, growth, skin health, wound healing, reproduction, protein structure, neurotransmitter, and insulin secretion
  • Low zinc levels could lead to impaired immune function, a tendency toward anxiety and depression (especially in women), and zinc adequacy may protect against breast and prostate cancers. 


  • Those on plant-centered diets who eliminate seafood and restrict iodized salt are most at risk of deficiency
  • Essential for the production of thyroid hormone and thyroid function
  • Iodine deficiency causes hypothyroidism, enlargement of the thyroid gland (goiter), and pregnancy-related problems

Vitamin K2

  • Supplementation is especially important for vegans or near-vegans since only small amounts are produced by the body and the nutrient is scarce in plant foods
  • Important for optimal bone health and heart health with aging 
  • Low K2 associated with a higher potential for fractures and bone loss and lower bone mineral density

Vitamin D

  • Those at risk of insufficiency are most people who work indoors or live in cool climates since sunlight is the primary source of vitamin D   
  • ÷For many people, adequate vitamin D levels are difficult to achieve from sunlight alone without damaging the skin
  • Important in building and supporting bone strength by enhancing calcium absorption; supports immune system
  • Low vitamin D linked to a higher risk of cancer, diabetes, cardiovascular disease, depression, and autoimmune conditions

Is There a Downside to Supplementation?

How can you be sure that what you are taking is worth the expense and the daily dedication, and most importantly, is safe? When I began looking for multivitamin and mineral supplements that I could give to patients with confidence, I was disappointed. Most multivitamins contain ingredients that could potentially be harmful, making the overall supplement cause more harm than good. Certain common ingredients in multivitamins like copper, beta-carotene, vitamin A, and vitamin E have been suggested in studies to have health-degrading, even cancer-promoting side effects. The multivitamins on the market all had too much of some things and too little of others. Even taking too much of something useful can be harmful. Plus, they almost always contained risky ingredients. For example, long term studies document that folic acid supplementation promotes breast and prostate cancer. As a result, I designed my own line of multivitamins that contain no folic acid, copper, beta-carotene, or vitamin A, all of which have been shown in studies to be harmful in excess amounts. 

The Best Use of a Multivitamin

The best use of a good multivitamin is not to counteract a nutrient-deficient diet, but to protect against possible deficiencies, providing nutrients whose requirements are not met with food alone. No multivitamin will lessen your risk of common diseases due to an insufficient diet, which will be lacking phytochemicals and contain toxins. The best situation is to eat a nutrient-rich diet, rich in whole plant foods and also take a carefully-designed supplement to address any micronutrient deficiencies that can undermine your health.


Foster M, Chu A, Petocz P, Samman S. Effect of vegetarian diets on zinc status: a systematic review and meta-analysis of studies in humans. J Sci Food Agric 2013, 93:2362-2371.

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.

Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Vitamin B12 [http://ods.od.nih.gov/factsheets/VitaminB12/]

Office of Dietary Supplements, National Institutes of Health. Dietary Supplement Fact Sheet: Zinc. [http://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/]

Swardfager W, Herrmann N, Mazereeuw G, et al. Zinc in depression: a meta-analysis. Biol Psychiatry 2013, 74:872-878.

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