Research is showing that Vitamin D, a hormone made in our skin after sun exposure, is both important and essential for our health.
According to Dr. Holick, 30 ng/ml is the minimum amount needed to get vitamin D’s benefits. Various experts recommend that optimal levels be between 50 to 100 ng/ml for disease prevention. Dr. Holick has found that blood levels up 100 ng/ml can “be both therapeutic and preventative of chronic diseases including common cancers”. Toxicity is not usually seen until levels exceed 150 ng/ml.
During the winter months, the average American has levels between 15 to 18 ng/ml. It's not surprising why so many people suffer from colds and flues in the winter. Vitamin D plays a powerful role in regulating our immune systems.
Are you at risk for Vitamin D deficiency?
If you live in northern latitudes, above the 37th parallel (which in the United States, extends from San Francisco, CA over to Newport News, Virginia), the angle of the sun is so low that hardly any Vitamin D can be produced in the skin between November and February, with other experts saying that October to April, is probably more accurate.
Sunscreen is another risk factor. A sunscreen with an SPF of 8 can reduce your skin’s ability to make Vitamin D by 90% and an SPF of 30 by about 99%. Holick's recommendation for sun exposure varies by location and skin type. The typical recommendation for the New England states is between 5 to 15 minutes of sunlight exposure to your arms and legs 2 to 3 times per week. If you continue sun exposure after this amount of time, you can use sunscreen or put on more clothing to prevent the damaging effects from excessive exposure to sunlight.
Another risk factor is relying on a multiple vitamin for your daily dose of D. Most only have 400 IU and even supplementing with 1000 IU of vitamin D a day will not raise blood levels above 30 ng/ml.
For adults who need to take a Vitamin D3 supplement, Holick recommends 2,000 IU per day with a safe upper limit of 10,000 IU/day depending on individual need. To consume the recommended 2,000 IU of Vitamin D in your diet, you would need to drink 20 glasses of fortified milk, eat 6 cans of sardines, 100 egg yokes, 7 oz of wild salmon or 20 bowls of fortified cereal each day. This is clearly a nutrient we were meant to get from the sunshine.
Holick feels that vitamin D is the missing “ingredient that could apply to prevention—and treatment, in many cases—of heart disease, common cancers, stroke, infectious diseases from influenza to tuberculosis, type 1 and 2 diabetes, dementia, depression, insomnia, muscle weakness, joint pain, fibromyalgia, osteoarthritis, rheumatoid arthritis, osteoporosis, psoriasis, multiple sclerosis and hypertension.”
Vitamin D has been found to reduce the risk of:
- Heart attacks by 50%
- Common cancer (colon, prostate and breast) by as much as 50%
- Infectious disease, including influenza by as much as 90%
- Type 1 diabetes by 78% if a child gets 2,000 IU of vitamin D/day in the first year of life.
Vitamin D can influence if a cell will become cancerous or not. If it does become cancerous, not only can it prevent the malignant cells from reproducing, but it can also help kill the cell or cut off the blood supply to the tumor. Holick believes that “anytime you become vitamin D-deficient, you put yourself at increased risk of potentially developing a malignancy because you’ve lost the policing ability of vitamin D to help keep cell growth in check.”
Holick reminds us that Vitamin D is not a cure-all, but obviously we can no longer ignore the benefits of having healthy levels—and the dangers of having too little. To find out your vitamin D status, ask your doctor to order a 25-hydroxy vitamin D test.
An excellent lecture by Dr. Michael Holick and a short clip that gives a brief overview of the book
- Holick, Michael F., Ph.D, M.D. The Vitamin D Solution. New York: Hudson Street Press, 2010.
- Adams, John S., Hewison, Martin. Update in Vitamin D. Journal of Clinical Endocrinol Metabolism. February 2010, 95(2);471-478.
- Autier, Philippe MD, Gandini, Sara PhD. Vitamin D Supplementation and Total Mortality: A Meta-analysis of Randomized Controlled
- Trials. Archives of internal Medicine. 2007;167(16):1730-1737