An Inconsistent Potency Of Vitamin D Found In Supplements [Study]

Vitamin D

Research recently published in The Journal of the American Medical Association (JAMA) Internal Medicine suggests there is an inconsistency between what is in the vitamin D supplement bottle versus what is on the label.

Over-the-counter (OTC) vitamin D supplements were tested, and researchers found each pill contained anywhere from 9 percent to 140 percent of the compound per dose, some pills providing negligible amounts while others contained significantly more in comparison.

Erin LeBlanc, an endocrinologist who led the study at the Kaiser Permanente Center for Health Research in Portland, Oregon, commented on their findings:

“We found the potency of these vitamin D supplements varied widely.”

LeBlanc was inspired to test over-the-counter vitamin D pills after finding similar inconsistencies in pills made at a compounding pharmacy for another study. Specially, made pills contained 52 to 146 percent of the labeled vitamin D doses.

LeBlanc and her team purchased 55 bottles of vitamin D supplements from 12 separate manufactures at five grocery stores. Promised potencies ranged from 1,000 to 10,000 international units (IUs).

The actual amounts varied from indicated dosages. One brand did contain consistent doses, a US Pharmacopeial Convention (USP) verified trademark product. The USP administers a quality verification program for supplements, but it is voluntary.

Vitamin D is fat-soluble and is responsible for intestinal absorption of calcium and phosphate. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). Because they are more likely to accumulate in the body, an excessive intake of fat-soluble supplements can lead to hypervitaminosis. Symptoms like vomiting and fatigue are due to toxic levels. Excess vitamin D can damage the kidneys. Adults 19 to 70 years old only require 600 International Units (IUs) of vitamin D per day, according to the Office of Dietary Supplements National Institute of Health.

Referring to vitamin D as a vitamin is technically a misnomer considering unlike other essential nutrients, vitamin D can be synthesized in the body from exposure to daylight. The organic chemical compound is only scientifically called a vitamin when it cannot be synthesized in sufficient quantities by an organism and must be obtained from their diet.

A deficiency of the vitamin can result in a condition known as rickets, a softening of the bones, as well as inhibit the body’s ability to properly absorb and process other nutrients.

The Food and Drug Administration (FDA) regulates dietary supplements as a category of foods and not as drugs. Therefore, supplement manufactures do not have to obtain FDA approval before distributing their product onto the market.

These findings indicate perhaps there should be more refined regulation regarding vitamin supplements to insure quality control and consistency.

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