I currently receive more questions about vitamin D than any other nutrient. Vitamin D is not only in the news, but many physicians are now routinely screening their patients for vitamin D deficiency. The attention being paid to vitamin D is encouraging, but there has been no sign that American medicine is willing to accept the need to support levels of other important nutrients. I addressed the challenge of single nutrient supplementation in a 2006 editorial Don’t Take a Lone Ranger Approach to Nutrition. It is available in the blog archive at drdalepeterson.com.

Vitamin D is an important nutrient. It has been called “the sunshine vitamin” because the body can synthesize it when the skin is exposed to adequate amounts of ultraviolet light. Unfortunately, almost no one over the age of twenty-one gets enough sun exposure to manufacture optimum amounts of vitamin D. This is compounded by the sun being too low on the horizon during the winter months to generate the necessary reaction in people living above the 35^th parallel. (In the United States the 35^th parallel defines the southern border of Tennessee.)

The primary reason vitamin D has received recognition among medical doctors is that optimum blood levels have been determined. Numbers motivate physicians to take action, so the ability to screen for vitamin D deficiency with a blood test has captured their interest.

The human body is capable of manufacturing two forms of Vitamin D. They are ergocalciferol or D₂ and cholecalciferol or D₃. D₃ is converted to D₂ in the liver. Neither form is active. When vitamin D activity is needed D₂ is changed to a hormonal form known as calcitriol. Calcitriol levels are tightly controlled by the parathyroid gland. Calcitriol levels also rise in response to low levels of calcium and high levels of phosphorus. It is ironic that physicians who are becoming concerned about low levels of vitamin D continue to prescribe medications to lower cholesterol, a substance that is required for the manufacture of vitamin D.

Vitamin D blood tests measure the level of D₂ in the bloodstream. It has been determined that a level of 30 ng/mL is needed if an individual is to experience the many health benefits of vitamin D. Some argue that the level should be above 40 ng/mL. Levels above 55 ng/mL are recommended for individuals who have multiple sclerosis, heart disease, diabetes, autism, or cancer.

Since blood tests measure D₂ levels it is not surprising that a prescription form of D₂ exists. I have seen several people who had been given a prescription of vitamin D₂, which is known as Drisdol. Studies have shown, however, that when taken orally the D₃ form of vitamin D is up to ten times more effective than D₂ in maintaining adequate stores of vitamin D. Therefore D₃ is the preferred form of vitamin D supplementation.

The interest in vitamin D has been driven in part by the ability to test for deficiency and in part by the recognition of the many roles it plays in the body. Traditionally viewed solely as a bone support nutrient, vitamin D is now being promoted as a key to solving a wide range of health challenges.

Over 95 % of people with osteoporotic bone fractures have been found to be deficient in Vitamin D. Supplementation has been shown to significantly decrease the risk of those fractures. This was initially believed to be due to the vitamin’s affect on bone calcium absorption, but it has been learned that optimum vitamin D levels also increase muscle strength and lessen the risk of falling. One study found that a group of elderly women given a combination of calcium and vitamin D experienced 49 % fewer falls than a control group that was given calcium alone. A review of available studies found a 25 % reduction in fractures in persons taking 700 – 800 IU of vitamin D daily. The reduction occurred with or without concurrent calcium supplementation leading researchers to conclude that supplementation of calcium above 800 mg. daily is unnecessary provided vitamin D is also provided.

Vitamin D appears to promote improved longevity. In 2007 researchers pooled the results of 18 vitamin D studies. The average supplemental amount of vitamin D in the studies had been 500 IU daily and the average length of the studies had been nearly six years. They found that the mortality rate in those supplementing vitamin D was 7 % less than that of people who were not taking supplemental vitamin D.

Vitamin D appears to protect against heart attacks and strokes. The benefit appears to be due to vitamin D’s ability to calm inflammation in the body. Inflammation in arterial walls is the trigger for plaque development. Vitamin D supplementation has also been shown to lower blood pressure, another risk factor for heart disease and stroke.

The anti-inflammatory effects of vitamin D are believed to be responsible for an observed decrease in type-1 diabetes in children given vitamin D supplementation early in life. Infants who were given 2000 IU of vitamin D daily during their first year of life were found to be 80 % less likely to develop diabetes than non-supplemented infants. Conversely, children who were found to have rickets, a softness of the bone related to vitamin D deficiency, were three times more likely to develop type-1 diabetes.

A strong correlation between vitamin D deficiency and multiple sclerosis exists. In 2006 a report of the analysis of the vitamin D levels of over 7 million U.S. military personnel found that the risk of developing multiple sclerosis dropped 40 % for each 20 ng/mL rise in circulating vitamin D₂. Individuals found to have a vitamin D₂ level above 40 ng/mL prior to age twenty were an incredible 91 % less likely than their peers to develop the disease! Another large study found that women taking 400 IU of vitamin D daily were 41 % less likely to develop MS than women not taking vitamin D supplements. Vitamin D may also offer hope to those who already have MS. One study found that the MS patients tended to relapse when vitamin D₂ levels fell below 19 ng/mL, but to go into remission when levels reached 24 ng/mL.

The connection between vitamin D levels and cancer susceptibility dates back to at least 1940, when an article observing that individuals with sun-related skin cancers were less likely to develop internal cancers was published. The author of the article suggested that it might be possible to prevent many cancers by regular sun exposure that was not intense enough to trigger skin cancer, but was sufficient to increase the amount of vitamin D being manufactured. The theory lay dormant for nearly seventy years, but in 2008 a review of studies involving women in 107 countries confirmed that sun exposure and higher vitamin D levels were associated with a decreased risk of breast cancer.

It has subsequently been learned that over 200 genes are responsive to vitamin D. Genetic expression plays a significant role in cancer development. Vitamin D appears to play key roles in regulating cell growth and cell death. These effects go far to explain the observed decrease in cancer risk with higher vitamin D blood levels. Cancers that have been shown to occur less frequently when vitamin D levels are high include those of the breast, colon, lung, prostate, and Hodgkin’s lymphoma.

Vitamin D has a remarkable ability to reduce pain, especially musculoskeletal pain. A high percentage of patients presenting with unexplained muscle or bone pain are deficient in vitamin D, and one study found that supplementation of vitamin D at levels of 5,000 to 10,000 IU daily for three months resolved the pain in 95 % of patients with unexplained chronic low back pain. A pain clinic found that chronic pain patients with vitamin D₂ levels below 20 ng/mL needed nearly twice the amount of pain relieving medication than those with levels above 20 ng/mL.

With so many benefits being reported, what can be said about the need for vitamin D supplementation? First of all, it is important to restate that vitamin D₃ (cholecalciferol) is the preferred form of supplementation. Secondly, most of the available studies have shown benefits with supplementation in the 400 – 800 IU daily range. Vitamin D has a half-life of 62 days in the body, so blood levels obtained from any particular dosage should be quite stable. If monitoring blood levels aim for a level of 35 – 40 ng/mL; if you have a chronic disease shoot for a level closer to 55 ng/mL. Remember, however, that the recommended levels were developed in a vacuum, without evaluating levels of other nutrients. It is not known what levels of vitamin D provide optimum benefits when the body is being given comprehensive support.

Vitamin D has a low toxicity risk. Supplementation in the range of 1,000 – 2000 IU daily should be adequate for most people. If necessary, doses up to 10,000 IU daily should be safe. Vitamin D may be the current superstar nutrient, but superstars rarely succeed as solo acts. When supplementing vitamin D don’t forget to provide a strong supporting cast.