In a new paper, researchers suggested that when recommending vitamin D supplements, doctors should look at each patient as having different requirements and not rely on “one-size-fits-all” guidelines.
The paper was written by a team at Rutgers and the University of California, San Francisco.
Vitamin D’s main function is to help the body absorb calcium.
Deficiency can cause delayed skeletal development and rickets in children and may contribute to osteoporosis and increased risk of fracture in adults.
According to the Institute of Medicine, people with less than 20 nanograms of vitamin D per milliliter of blood are deficient.
The Endocrine Society set a higher threshold of 30 nanograms. Neither guideline is more definitive than the other at this time.
Recommendations based on earlier studies using a number of different tests for vitamin D levels persist and, not surprisingly, current guidelines vary.
It is not clear that the most optimal levels for vitamin D are the same for Caucasians, blacks or Asians alike.
Vitamin D supplements work best when taken with calcium for rickets and bone loss that occurs with aging.
Elderly people who are vitamin D deficient benefit from supplementation as protection against fracture.
However, studies did not show supplements to be beneficial as protection against a fracture if the elderly person was already sufficient in the vitamin.
The researchers also noted that more vitamin D supplementation is not better.
Previous studies have shown that very high doses of vitamin D (300,000-500,00 iu taken over a year) seem to increase fracture risk.
(The National Academy of Medicine recommends 400 IU/day for infants, 600 IU/day for people age 1 to 70 and 800 IU/day for people over 70; the Endocrine Society suggests doses up to 2,000 IU/day for adults.)
Although vitamin D supplementation has been shown to reduce overall mortality and some studies suggest that vitamin D might be beneficial for immune function, cancer, and cardiovascular health, a consistent benefit of vitamin D supplementation has yet to be shown.
However, most studies have not discriminated between participants who are vitamin D sufficient or deficient.
The team suggests that future work needs to find out the optimal levels for vitamin D for people with different ethnic backgrounds.
It is also important to see how the health benefits of vitamin D can be changed by its dose.
One author of the study is Sylvia Christakos, a professor at Rutgers New Jersey Medical School.
The study is published in the journal Metabolism.
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