What to Tell Patients about Vitamin D

By Annette Boyle, MDalert.com contributing writer.

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  • According to Institute of Medicine report, vitamin D supplementation does have some health benefits in adults.
  • Serum levels too high and too low are associated with increased mortality.
  • Deficiency associated with significantly increased risk of stroke or myocardial infarction.
  • Problems have been identified with tested supplements often not containing any vitamin D.

A Great Deal of Mixed Data about Vitamin D

If your patients are asking you about taking vitamin D supplements, this article can help formulate answers.

Vitamin D (See Figure.) refers to a class of fat-soluble secosteroids that have a wide range of effects in humans. The most important compounds in this group are vitamin D3, cholecalciferol, and vitamin D2, ergocalciferol. Both are essential to normal development in humans. The natural sources for these nutrients are diet and exposure of the skin to sunlight.

Figure. Cholecaliferol.
Source: Sbrools.
Licensed under CC BY-SA 3.0 via Wikimedia Commons



The clinical thinking regarding supplementation hinges on the controversy and the reality of sun exposure. While moderate supplementation is beneficial, for instance, for people in northern climates who often get very little sun exposure in winter. If they are not getting vitamin D in their diet, they can be deficient.

On the other hand, in the summer, exposure to the sun in northern climes can be harmful to unprotected skin. Repeated exposure puts people at significantly increased risk of melanoma. Best practices seem to suggest that you tell patients to make sure they get 400IU/d to 800IU/d and to protect their skin if they are in the sun.

Clinicians at Cleveland Clinic, for instance, recommend 1000IU to 3000IU supplementation per day, throughout the year. They also discourage exposure to the sun. The IOM’s recommended daily allowance (RDA) ranges from 400IU/d in individuals aged <70 years and 800IU in older people. Deficiency has been associated with significantly increased risk of stroke or myocardial infarction.

Questions remain regarding the association of vitamin D with reduced risk of influenza, seizures, autism, Alzheimer disease, arthritis, asthma, hypertension, multiple sclerosis, and a host of other conditions.

All Things in Moderation

A recent study of nearly 250,000 Danes indicated that if serum levels of vitamin D get too high (above 100 nmol/L or 40 ng/mL), patients have a 30% increased risk of cardiovascular mortality. If levels are too low (below 50 nmol/L or 20 ng/mL), the risk of death from stroke or myocardial infarction doubles.

The National Institutes of Health note that other studies have reported an association between serum levels of 75-120 nmol/L or 30-48 ng/mL and increased risk of all-cause mortality, pancreatic cancer, cardiovascular events, and fall and fractures. A serum level of about 50 nmol/L (20 ng/mL) reflects a vitamin D intake level consistent with the recommended daily allowance.

If your patients need to increase their vitamin D consumption, recommend more salmon, which has more than 100% of the estimated average requirement in each serving. Tuna and foods fortified with vitamin D such as orange juice, milk, almond milk, and yogurt can contribute 20% to 40% of the daily requirement, while eggs and fortified cereal can provide 10% or more.

Supplements can provide a boost, too, if they actually contain vitamin D. A number of Updated Meta-Analysis

In 2010, the Institute of Medicine (IOM) conducted a systematic review of 1000 studies and reports on the efficacy of vitamin D. “This thorough review found that information about the health benefits beyond bone health—benefits often reported in the media—were from studies that provided often mixed and inconclusive results and could not be considered reliable.” An Agency for Healthcare Research and Quality update in 2014 generally supported the 2010 report, but did find some evidence that vitamin D supplementation may reduce the risk of preeclampsia.

Vitamin D promotes absorption of calcium and enables normal mineralization of bone, bone growth and bone remodeling and the two nutrients are generally taken (and studied) together. Sufficient levels of vitamin D in the first few years of life prevent rickets in children. Sufficient levels later in life can prevent osteomalacia in adults and reduce the risk of osteopenia and osteoporosis.

The IOM also noted that the RDAs assume that individuals obtain all of their vitamin D through diet. While national surveys show that most Americans do not consume the RDA for vitamin D, average blood serum levels of the vitamin have been found to be above the 20 ng/mL minimum recommended for good bone health. The likely explanation for this disparity is that most people get an appreciable percentage of vitamin D from cutaneous synthesis through exposure to sunlight.

If your patients live in a nursing home or other institution, or northern climate (like Cleveland, Ohio, home of the Cleveland Clinic, or Rochester, Minnesota, where many patients of the Mayo Clinic are located), they may not receive enough sunlight in the winter to synthesize the necessary amounts of vitamin D. Over the course of the winter, these people can become vitamin D deficient. Older patients in any climate can be expected to have trouble synthesizing vitamin D.

Studies have shown that steroids, orlistat, phenobarbital, phenytoin, and cholestyramine inhibit the absorption of vitamin D. Obese individuals, including those who have had gastric bypass surgery, those with inflammatory bowel disease, and those with darker skin may also require greater vitamin D supplementation, according to the National Institutes of Health.

Supplements can provide a boost, too, if they actually contain vitamin D. A number of recent reports, however, have found that many supplements sold in North America do not contain the stated ingredients, so maybe it’s best to stick with a tuna sandwich and a glass of milk.


Based on systematic reviews by the
Institute of Medicine and the Agency for Healthcare Research and Quality.


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