Mar 31, 2020
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Vitamins and supplements

Search on-line the topic of vitamins and minerals and see what the public receives for information.  There are numerous conflicting opinions available on-line and in scientific studies.  Basic guidelines are that additional vitamins and minerals are not needed if one consumes a balanced diet based on USDA’s plate method.  If a balanced diet is in question, a MVI with minerals that doesn’t go above 100% RDAs for most healthy adults and is a good insurance policy.  There are always exceptions to this rule.  Times like pregnancy increase needs for certain nutrients.  (1)

In healthcare, we need to remember the anatomy and physiology of how nutrients are absorbed.   Any GI resection or malabsorption issues, will necessitate an increase of certain nutrients.   Any history of gastric bypass surgery, ileostomy, Crohns disease, ulcerative colitis, and gastrectomy are a few examples of resections or diseases with malabsorption (1, 2, 3).

Vitamin and mineral deficiencies are still diagnosed and need to be treated with the prescribed dosage that is usually higher than the RDA for a prescribed length of time.   There are medications that interfere with absorption of a nutrient or increase the need for a nutrient, examples are Lasix, Methotrexate, proton pump inhibitors (1, 3, 4).

Vitamins are divided into water-soluble and fat-soluble.   Most sources cite that high doses of water soluble vitamins are not an issue, since what is not used is eliminated via urine.    However, in certain individuals some water soluble vitamins in high dosages can be damaging.  Gastrointestinal disturbances, kidney stones, and excess iron absorption, particularly for individuals with excessive iron absorption due to hereditary hemochromatosis, is cited as the possible adverse effects of excessive consumption of vitamin C (1, 5).  High dosages of one nutrient may affect the absorption or use of another nutrient causing an unintended deficiency.  For example, high-dose iron supplements can decrease zinc absorption and high amounts of zinc can inhibit copper absorption (1, 6).    Fat-soluble vitamins have been shown to accumulate in body over time, and can be toxic if consumed in large dosages over certain length of time.

There are a few independent organizations that offer “seals of approval” that may be displayed on certain dietary supplement products.  These “seals of approval” do not mean that the product is safe or effective; they provide assurance that the product was properly manufactured, that it contains the ingredients listed on the label and that it does not contain harmful levels of contaminants (7).  Some examples of programs that provide this service: Consumerlab.com, NSF International dietary supplement certification, and U.S. Pharmacopeia dietary supplement verification program (7).

Dietitians have been trained to use evidence-based medicine, and for many of the high dosages of most vitamins or minerals do not meet the A or B Grade for Evidence to support use.   This means further research may change these recommendations, but let’s allow science to dictate our choices.

 

References:

  1. Marra, MV, et al. Position of American Dietetic Association: nutrient supplementation. J Am Diet Assoc. 2009 Dec;109(12):2073-85.
  2. Vitamin B6, Dietary Supplement Fact Sheet. NIH.  https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional. Accessed August 8, 2017.
  3. Vitamin B12, Dietary Supplement Fact Sheet. NIH.  https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional.  Accessed August 8, 2017.
  4. Folate, Dietary Supplement Fact Sheet. NIH.  https://ods.od.nih.gov/factsheets/Folate-HealthProfessional.  Accessed August 8, 2017
  5. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academies Press; 2000.
  6. Zinc, Dietary Supplement Fact Sheet. NIH.  https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional.  Accessed August 8, 2017
  7. Dietary Supplement Fact Sheet. NIH. https://ods.od.nih.gov/Health_Information/ODS_Frequently_Asked_Questions.aspx#Compare.  Accessed August 8, 2017.