A peer-reviewed journal that offers evidence-based clinical information and continuing education for dentists.

The Vitamin D Conundrum


Heated discussion is ongoing about how much vitamin D is needed to sustain optimal health. There is agreement that this vitamin is necessary for calcium absorption, while others see additional roles for vitamin D, including control over normal cellular metabolism in different cells and tissues throughout the body.

At present, there are two ways to increase the amount of circulating vitamin D:

  1. Exposure to sunlight
  2. Dietary/nutritional supplementation

Unfortunately, not everyone receives sufficient exposure to sunlight, especially during the winter, and vitamin D has few natural dietary sources besides whole milk and yogurt, various species of fish, and fortified products.

There is disagreement about what circulating blood levels are both safe and effective. The United States Food and Drug Administration suggests supplementation should be limited to 400 to 600 international units (IU) per day. This is due to the concern that larger amounts may lead to hypercalcemia. Other groups suggest that increased supplementation, within certain accepted limits, has not been shown to produce this problem.This discussion was highlighted by two recent articles.

The Proceedings of the Third International Conference on Controversies in Vitamin D was published in 2020.1 A group of experts from around the world addressed several areas concerning the use of this vitamin as a dietary supplement. They agreed that the optimal way to measure levels is the 25-hydroxy vitamin D test (250HD).

The controversy begins when the safety and efficacy of levels greater than 400 to 600 IU are taken daily. As noted, most international regulatory bodies suggest these levels for individuals without daily exposure to sunlight. The concern for larger amounts of vitamin D supplementation stems from the hypercalcemia found during the 1930s and 1940s. These levels were produced with doses of up to 600,000 IU per day.

The second paper suggests that higher doses may be beneficial without producing hypercalcemia. The authors reviewed the literature and reported on group of 418 patients who had received daily oral doses of 5,000 to 50,000 IU for a year or more.2 They compared these patients to a group that did not receive supplementation (777). The authors found no evidence of hypercalcemia in either group.

They argue that these amounts are safe since exposure to sunlight can produce 10,000 to 25,000 IU without increasing 250HD levels. In their literature review, the authors cited other studies suggesting that higher levels of supplementation could help with systemic problems including Alzheimer disease, asthma, Crohn disease, psoriasis, and some cancers. Unfortunately, proving these links will be difficult because vitamin D is inexpensive to manufacture, therefore few companies will be interested in sponsoring research. So the debate will continue to suffer from the lack of needed studies.

Thomas G. Wilson Jr., DDS

Editor in Chief


  1. Giustina A, Bouillon R, Binkley N, et al. Controversies in vitamin D: a statement From the Third International Conference. JBMR Plus. 2020;4:e10417.
  2. McCullough PJ, Lehrer DS, Amend J. Daily oral dosing of vitamin D3 using 5000 to 50,000 international units a day in long term hospitalized patients: insights from a seven-year experience. J Steroid Biochem Mol Biol.2019;189:228–239.

From Decisions in Dentistry. September 2023; 1(8):6

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