Vitamin D: Critically Important For Health – How Much is Enough?
By Nathan Wei
Our ancient ancestors probably didn’t require vitamin D in food because they got sufficient D through skin exposure to ultraviolet rays from the sun. However, with gradual migration from areas near the equator to more distant areas where sunlight exposure become more problematic, the adaptation that allowed people to live in more temperate climates was to develop lighter skin in order to absorb vitamin D more efficiently. An exception would be Eskimos who get vitamin D from their diet.
Unfortunately, this adaptation has had its shortcomings. Today, unless they spend a great deal of time outdoors, people need supplemental vitamin D. (The flip side of this is the recent concern regarding sun exposure and the development of skin cancers).
So what does vitamin D do?
In the bones, vitamin D helps the body to absorb calcium. Sufficient vitamin D can build bone density. About 1,000 International Units (IU) of vitamin D per day can lower the risk of fracture in older people.
Vitamin D also lowers the risk of falling by improving balance and muscle strength. Specific vitamin D receptors in muscle indicate that this vitamin has an important role in muscle function.
Periodontal disease is the leading cause of tooth loss and is due to chronic inflammation. This leads to receding gums and the tooth starts to wear away. Vitamin D suppresses inflammation and therefore wards off gum disease. People with low vitamin D levels have an increased level of periodontal disease.
Vitamin D has an important effect on maintenance of immune function. Vitamin D inhibits angiogenesis which is the formation of new blood vessels, an important factor in tumor growth. Vitamin D also appears to prevent tumor cells from metastasizing. Vitamin D may have an important role in reducing the risk of colorectal cancer and possibly pancreatic cancer.
Research exists that supports the notion that vitamin D promotes insulin secretion from beta islet cells in the pancreas and has influence on insulin resistance. People who are overweight have an increased need for vitamin D.
Vitamin D supports the immune system. It decreases the production of T-1 cells responsible for autoimmunity and increases the production of T-2 cells which help keep T-1 cells in check. This immune effect may explain why vitamin D may help prevent the development of Type 1 diabetes.
Vitamin D levels are often low in patients with rheumatoid arthritis. This could be explained by the hyperactivity of the immune system that accompanies vitamin D deficiency.
There is tantalizing evidence that vitamin D helps not only with bone growth but also with cartilage nutrition. This means that it may be essential for preventing or slowing down osteoarthritis.
So how much vitamin D is needed? At the very minimum, a person should shoot for 1,000 IU a day. Vitamin D supplements are best if they are vitamin D3 (cholecalciferol) rather than vitamin D 2 (ergocalciferol) which is less potent.
One caveat: too much vitamin D could possibly lead to more kidney stone formation so if you are prone to kidney stones you should check with your physician before taking more than 1,000 IU per day. Otherwise, a person could probably safely take 2,000IU – 4,000 IU a day.
Monitoring of vitamin D levels is probably a very good idea.
One area where people are almost always very vitamin D deficient is the nursing home. The lack of sun exposure coupled with diets inadequate in vitamin D make for a terrible combination.
Nathan Wei, MD, FACP, FACR is a rheumatologist and Director of the Arthritis and Osteoporosis Center of Maryland (http://www.aocm.org). He is a Clinical Assistant Professor of Medicine at the University of Maryland School of Medicine and consultant to the National Institutes of Health. For more info: Arthritis Treatment