Juvenon Health Journal Vol. 5 No. 4, April 2006
Vitamin D has long been known to have potent properties against cancer. A recent study analyzed six different determinants of vitamin D exposure: diet, supplements, skin pigmentation, adiposity, geographic residence (latitude) and leisure-time activity. Using multivariable models, the study concluded that low levels of vitamin D may be associated with increased cancer incidence and mortality in men. To read the peer-reviewed article,click here.
“Prospective Study of Predictors of Vitamin D Status and Cancer Incidence and Mortality in Men.” Journal of the National Cancer Institute, Vol. 98, No. 7, 451-459, April 5, 2006.
By Benjamin V. Treadwell, Ph.D.
Why a second successive article (third overall) on vitamin D? (See Vol.5 No.3Vitamin D: A Hormone with New Health Benefits and Vol.2 No.6 Vitamin D: A Vitamin in Need of Revision for previous Juvenon articles on vitamin D). Because startling new information keeps coming in.
A few of the diseases that may be associated with an inadequate supply of vitamin D include: cancer (prostate, breast, ovarian, bladder, digestive system), diabetes, osteoporosis, congestive heart failure, atherosclerosis, autoimmune diseases (multiple sclerosis, psoriasis, rheumatoid arthritis), and additional diseases involving inflammation. Today’s discussion will focus on cancer and diabetes.
Over 70 years ago, investigators hypothesized that sun exposure lowers the risk of cancer. Others later demonstrated an association between the latitude one lives in and incidence of cancer. Additional studies led to the discovery that skin exposure to sunlight was activating the synthesis of vitamin D. In fact, it has been demonstrated that as much as 20,000 IU of vitamin D are produced by 20-30 minutes of exposure of the skin (of a youthful individual) to the UVB rays from the sun. However, diet and other factors besides sunlight affect circulating levels of vitamin D. Fat, dark skin and aged skin are associated with lower blood-levels of vitamin D. Supplemental vitamin D may be far more important than previously realized.
What is the evidence that vitamin D can help prevent cancer?
The work I am describing today involves data taken from “The Health Professional Follow-Up Study”, initiated in 1986 to help determine the causes of cancer and other chronic diseases. The study population consists of 51,529 U.S. male medical professionals age 40-75 at the start of the study. The investigators determined each subject’s average daily vitamin D intake by estimating the amount of sun exposure, dietary D intake, and vitamin D taken in a supplement form.
The results were impressive. Those subjects determined to have the highest vitamin D levels, equivalent to at least 1,500 IU of D/day, had a 29% lower incidence of cancer mortality, compared to those determined to have the lowest level of vitamin D. If daily vitamin D levels of Americans were increased to 1,500-2,000 IU, one could project that the result would be 85,000 fewer cancer deaths in the U.S. per year!
Vitamin D is associated with a decrease in type 2 diabetes in women.
Additional benefits of high doses of vitamin D are based on “The Nurses Health Study Cohort” initiated in 1976. This study included 121,700 U.S. female nurses age 35-55 at the start of the study, who were monitored for their daily intake of vitamin D and calcium. The results demonstrated that women with a vitamin D intake of more than 800 IU/day had a 23% lower risk of developing type 2 diabetes as compared to those with less than 400 IU/day. Interestingly, a separate population of nurses taking high calcium (more than 1200 mg/day) had a 21% lower incidence of diabetes compared to those taking less than 600 mg/day. A third group of nurses, consuming more than 800 IU of vitamin D and more than 1200 mg of calcium, had the most impressive statistical result. Their incidence of diabetes was 33% lower than those with a daily intake of less than 400 IU of D and less than 600 mg of calcium.
How does Vitamin D elicit these effects?
The answer to this question is currently under intense investigation. There are a number of speculations. First, vitamin D requires the presence of its cognate receptor to elicit a biological effect.
It is now known the receptor for ‘D’ is on virtually all cells, including those of the insulin-producing beta cells of the pancreas. There is evidence to support a role for ‘D’ in regulating calcium levels, which in turn may help regulate insulin production and glucose levels. The bottom line is that if you don’t have sufficient levels of this vitamin and calcium, the beta cells of the pancreas become dysfunctional, and insulin regulation is impaired, resulting in the diabetic state.
The possible explanation for vitamin D’s effect on inhibiting cancer is even more speculative. However, recent work with cells in culture demonstrates that the vitamin inhibits the production of specific enzymes that allow cancer cells to grow and metastasize. The vitamin also has been shown to inhibit the production of a cellular protein, TNF-alpha, elevated levels of which are associated with inflammation and cancer. This can also pertain to diabetes as well as atherosclerosis, psoriasis, MS, and congestive heart failure, as this protein too has been implicated as a key player in tissue inflammation commonly associated with and contributing to these diseases. It appears that higher levels of this vitamin (1,500-2,000 IU/day compared to the current RDA of 200-400 IU/day) are required to produce the positive health responses in tissues described above. At these higher doses, the vitamin plays the role of a regulator of the immune system to bring the players of cellular immunity into balance (homeostasis).
So what are we to do?
Those who have dark skin, are over age 50, or live in areas with minimum sunlight might discuss taking higher levels of vitamin D with their health professionals. (The specific form of vitamin D is important. For example, D3 is 4 times more active D2. See our Ask Ben column for details.) How much? The government-recommended upper limit is 2,000 IU/day (equivalent to 20 glasses of milk/day). However, there is much controversy from those who are the experts in the field who state that indeed this level may be too conservative. At least 1,500 IU/day are required to have the optimum health effects observed in the research described above. For now, the decision is up to you and your health professional as to whether you should consider a daily dose comparable to what these recent studies suggest.
I have heard that there are many forms of vitamin D. What form should we be taking as a daily vitamin supplement?
F.R., via email
Benjamin V. Treadwell, Ph.D. is a member of Juvenon’s Scientific Advisory Board and formerly an associate professor at Harvard Medical School.
Send your questions to AskBen@juvenon.com.
Answers to other questions are available athttp://juvenon.com/product/qa.htm.
You are correct. There are several forms of vitamin D. Enzymes in the liver, kidney and other tissues of the body modify the vitamin by adding different chemical groups such as hydroxyl groups to the core vitamin. Some supplements contain vitamin D2 (ergocalciferol), a precursor of vitamin D3. D2 is only 1/4th as active as D3. The conversion of vitamin D2 to the more active form vitamin D3 (cholecalciferol) is a spontaneous reaction in the body. Once vitamin D3 is produced, it requires chemical conversion in the liver and kidney to form 1,25-dihydroxyvitamin D (calcitriol), the physiologically active form of vitamin D. Therefore I recommend you make sure the vitamin D you are taking on a daily basis is the D3 form.