The Sunshine Vitamin
by author Deborah Cramer

Vitamin D may be one of the most important nutrients for preventing a host of diseases and improving longevity. This month’s Research Watch discusses the new research about this long-overlooked vitamin and how it may be critical to long-term health.

Most of us know that vitamin D is important for supporting bone health, preventing rickets, and tooth mineralization. However, nearly every tissue and cell in the body has a receptor for this vitamin, and it is well established that vitamin D is an important regulator for cell differentiation, programmed cell death, and the growth of new blood vessels.

Vitamin D is stored by the human body in two forms. Vitamin D2 and vitamin D3 are available from food or supplementation; D3 is also made in the skin after exposure to the sun’s UVB rays.

In 1980 epidemiologists noticed that mortality rates from colon cancer were significantly higher in the northeast United States and Canada compared to rates in the west, south, and southwest. Their work was the first to link cancer and vitamin D intake, and it sparked an explosion of studies correlating lack of vitamin D intake with a host of diseases.

Cancer Incidence and Mortality

Scientists around the world began to conclude that exposure to sunshine, and by implication, vitamin D, may help to prevent cancer. In 2001 British epidemiologists observed that patients with lower lifetime sun exposure developed prostate cancer at a younger age.

Norwegian researchers reported that sun exposure at diagnosis may affect mortality. From an analysis of more than 27,000 men and women diagnosed with colon cancer, death rates were 20 to 30 percent lower for cancers diagnosed in late summer and autumn than those diagnosed in the winter and spring. Similar findings have been reported for other cancers.

Multiple Sclerosis

Researchers also report a correlation between geography, cases of multiple sclerosis (MS), and vitamin D intake. Northern Europe and Canada have the highest MS rates in the world, with Canada’s rates four times higher than those in the southern United States. Recent work hypothesizes that vitamin D may have an immune and disease-modulating effect in MS.

Diabetes

Several studies show an inverse relationship between vitamin D and type 1 diabetes. For example, a Finnish cohort study followed a group of children from birth through adulthood. The results showed an 80 percent decline in the risk of type 1 diabetes for those children who received high doses of vitamin D. A recent meta-analysis supports the Finnish work, concluding that vitamin D supplementation in early childhood reduced significantly the risk of developing the disease.

Sunshine, Supplements, and Salmon

Dwellers north of latitude 37 degrees will probably need supplementation to maximize vitamin D intake. The Canadian Cancer Society has joined other scientists in recommending a minimum daily intake of 1,000 IU, especially in fall and winter, from a combination of sunshine, supplements, and diet. The Canadian Pediatric Society recommends that breastfeeding women get 2,000 IU daily.

Most people will need to rely on food and supplements to get reach 1,000 IU. Only a few foods contain vitamin D, and while 1 Tbsp (15 mL) of cod liver oil or a single serving of wild salmon meets the daily recommendation, many will find it easier to rely on supplements. Vitamin D is available in calcium supplements, multivitamin formulations, and as a stand-alone product. Just be sure that at least one of the supplements includes vitamin D3. Take special care when giving supplements to children; large doses can be toxic.

Although it is not a cure for cancer, MS, or childhood diabetes, vitamin D does seem to provide protective benefits against a host of diseases. What more can you ask from a sunny day?

Deborah Cramer is a long-time science and technical writer for whom happiness is a sun-warmed breeze, a hyacinth blue sky, and a gently swaying hammock.

Source: alive #310, August 2008