What do osteoporosis, multiple sclerosis, diabetes, insulin resistance, arthritis, muscle weakness, gum disease and cancers of the colon, pancreas, prostate and breast have in common? These conditions belong to a growing list of illnesses that vitamin D may help to prevent.
Vitamin D is a hormone produced in the body by the action of sunlight on the skin. Practically every cell in the human body has receptors for vitamin D. It impacts cell growth and proliferation, how the body makes bone, muscle, and insulin, and how the immune system works. That’s a lot for one little vitamin, but it underscores the importance of vitamin D for health. We should all make sure that we are getting enough.
That’s not easy to do for most of the US from November through February. The angle at which sunlight enters the atmosphere in winter doesn’t allow for much penetration of the ultraviolet B radiation necessary for making vitamin D in the skin. When the clocks are turned back at the end of October, it is safe to assume that if you live above the 35th degree northern latitude (the line from about Los Angeles to Atlanta) you will not be able to make any vitamin D until the clocks are turned forward in March.
The evidence linking vitamin D to health problems has exploded within the past 10 years. This has led researchers to review the current recommendations for vitamin D intake, and many believe that the recommendations need to be increased considerably.
Bones:
Vitamin D helps the body absorb calcium. When vitamin D intake is adequate, less calcium is needed to improve bone density and to prevent bones from breaking.
Muscle:
Muscle tissue has receptors for vitamin D, which suggests that it is important for muscle function. Older women given vitamin D had an increase in muscle growth. Older people with high vitamin D blood values performed better on tests that require muscle strength and balance, and have a lower risk of falling.
Gums:
Many studies have identified a link between low vitamin D levels and gum disease. In one study, older people given 700 IU of vitamin D and 500 mg of calcium daily for three years had 60% less tooth loss. Vitamin D is thought to suppress the inflammation that influences gum disease.
Cancer:
Animal studies are quite remarkable in showing that vitamin D makes cancer cells less likely to multiply, and more likely to die. The evidence in people is more complex, but higher vitamin D levels are associated with decreased risk of certain cancers, and vitamin D is viewed as the most promising nutritional adjunct for the treatment of cancer.
Diabetes:
Preliminary evidence suggests that vitamin D may prevent Type 2 diabetes by promoting insulin secretion and decreasing insulin resistance. Many diabetics are overweight, which increases the body’s need for vitamin D.
Osteoarthritis:
Low blood levels of vitamin D have been associated with knee and hip arthritis. In normal bone growth, cartilage cells lose their vitamin D receptors when the bones stop growing. When a person has arthritis, the cartilage cells are stressed and vitamin D receptors reappear. It is believed that vitamin D has an importance in cartilage as well as bone.
Immune system:
Vitamin D is important for a normally functioning immune system. Immune cells use vitamin D to make proteins necessary to fight bacteria.
Vitamin D’s impact on autoimmune disease is also being studied. Children who are newly diagnosed with Type 1 diabetes were noted to have low blood values of vitamin D. In Finland, researchers are giving infants at high risk for Type 1 diabetes 2,000 IU of vitamin D daily to see if it can ward off the disease. A study on multiple sclerosis (MS) showed that women who supplemented with at least 400 IU of vitamin D daily were 40% less likely to develop MS. People with rheumatoid arthritis (RA) also often have low blood levels of vitamin D. Researchers at Penn State University are giving patients 1,000 IU of vitamin D a day to see if helps control the inflammation associated with RA.
How Much?
Consider that the skin makes thousands of units of vitamin D when exposed to the sun. The current recommendations for vitamin D (200-600 IU depending on age) were made to prevent rickets (softening of bones due to vitamin D deficiency) and to help prevent osteoporosis. A safe upper limit of 2,000 IU was set based on a study that never measured blood levels of the vitamin. Researchers are currently giving patients anywhere from 1,000 IU to 6,000 IU of vitamin D daily without adverse effects.
Very few foods contain vitamin D, and supplementation during the winter months is necessary to get an adequate amount. Supplementing with 1,000 IU of vitamin D daily seems warranted in light of new evidence supporting the importance of vitamin D for health. A typical multivitamin contains 400 IU of vitamin D. Add to that an extra individual vitamin D supplement containing 400 IU and a couple cups of low fat milk (100 IU per cup) and you’ll get 1,000 IU of vitamin D daily. Make sure that your vitamin D supplement is D3 (cholecalciferol) and not the less potent D2 (ergocalciferol). Those with special conditions should talk with their doctor about taking more.
