By Shmuel Shields, Ph.D., N.Y.S. Certified Nutritionist
Have you heard the latest news on vitamin D? In recent years, media attention has focused the spotlight on this particular vitamin, with claims that low levels are linked to a host of illnesses – including osteoporosis, cancer, diabetes, gum disease, arthritis, and heart disease. Medical researchers have even found that people with the lowest vitamin D levels report having significantly more cases of flu and colds than those with higher levels.
Initial scientific research highlighted the critical role that vitamin D plays in bone health. Although usually categorized as a fat soluble vitamin, vitamin D actually functions as a hormone in the body. It helps to activate calcium and phosphorus – both known to be essential minerals for keeping bones strong – into the bloodstream. When the body is depleted of vitamin D or has an insufficient supply, it turns to the bones for replenishing these two minerals. This can then thin the bones and contribute to osteoporosis.
A diagnosis of osteoporosis – in which bones become fragile and more likely to break – is of particular concern to women. The National Osteoporosis Foundation reports that millions of women over the age of 50 will be diagnosed with this condition; one in two women (compared to one in eight men) over 50 will have an osteoporosis related fracture in their lifetime.
Recent studies further point to the important role that vitamin D plays in immune system functioning. According to Dr. Michael Holick of Boston University Medical Center, immune cells have vitamin D receptors, and these cells activate vitamin D in response to infection. Initially, immune cells use vitamin D to fight a virus; then they use it to temper the overall immune response and limit inflammation. This theory would explain the findings that people with the lowest vitamin D levels report having significantly more cases of colds and flu than those with higher levels. In addition, it has been found that Americans living in the South have lower rates of certain cancers than those living in the North. Based upon this, Consumer Reports on Health concludes that higher vitamin D levels, achieved through greater sun exposure, may also have protective effects against cancer.
Unfortunately, vitamin D is not readily found in most foods; the only significant food source is fatty fish (salmon, sardines, herring, bluefish, and mackerel). Known as the sunshine vitamin, it is also made by your skin from the ultra-violet rays in sunlight. Consequently, deficiencies are especially common in Americans living in the North, who consume little fish and tend to have very limited sun exposure.
According to the Harvard Health Letter, some experts claim that the current RDA (Recommended Daily Allowance) of 400 IU (International Units) of vitamin D is low, and that adolescents, adults, and seniors should aim for 800-1000 IU per day. Since good food sources of natural vitamin D are extremely limited, it becomes virtually impossible for many people to get optimum levels without supplementing.
You can get some idea of your daily intake by calculating vitamin D amounts in supplements and fortified foods. Keep in mind that there are two types of vitamin D; D3 (cholecalciferol) is better absorbed and found in better quality supplements, whereas D2 (ergocalciferol) does not get absorbed by the body as well. Due to the general public’s lack of knowledge about vitamin D, it is highly advisable to have your physician check your vitamin D level and give you some guidelines for safe sun exposure and proper nutritional supplementation.