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Vitamin D May Lower Risk of Ovarian, Breast, Kidney, and Colon Cancers
2/26/2009
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New analyses affirm vitamin’s anti-cancer clout, and expand list of preventive benefits to stealthy, deadly ovarian tumors

by Craig Weatherby


The evidence for vitamin D as a powerful cancer-preventer continues to grow at a rapid rate.


The results of two new data analyses indicate that high dietary intake of the “sunshine-and-seafood” vitamin can cut the risk of colon and breast cancers by 50 percent.


And these results follow the findings of two studies by the same team, which indicate that greater sun exposure cuts the risk of ovarian cancerone of the most deadly kindsand the risk of kidney cancer.


Sun exposure produces vitamin D in the body, which is why greater sun exposure yields reduced cancer risks, overall: benefits that outweigh greatly the possible increase in skin cancer risk produced by over exposure to sunespecially in fair-skinned peopleand sun burn.


The research team responsible for the new data analysis and related prior investigations included the world’s leading vitamin D scientists:

  • Professor Edward Giovannucci, M.D., Sc.D., of Harvard University.
  • Professor Michael F. Holick, M.D., Ph.D. of Boston University.
  • Professors Edward Gorham, Ph.D., Frank C. Garland, Ph.D., and Cedric F. Garland, Dr. P.H. of the University of California San Diego.
  • William B. Grant, Ph.D., founder of the Sunlight, Nutrition and Health Research Center in San Francisco (SUNARC).

The encouraging new findings fit with the same team’s prior analysis of 63 studies of vitamin D status and cancer risk.


That 2005 meta-analysis found that if people consumed more vitamin D, it could reduce their risks of breast, colon, and ovarian cancers by half (see “Higher Vitamin D Intake Could Cut Cancer Risk in Half”).


And last December, the same group published studies showing that low exposure to sunlight is linked to higher risk of ovarian and kidney cancer (Garland CF et al Am J Prev Med 2006; Mohr SB et al 2006). Both analyses employed previously unavailable data from a new World Health Organization database of cancer incidence, mortality and prevalence in 175 countries (GLOBOCAN).


Vitamin D and breast cancer risk

The UCAL San Diego team examined data from two large epidemiological studiesthe Nurses’ Health Study and the St. George's Hospital Studywhich included 1,760 women (Gorham ED et al 2007).


Their analysis showed that the women with the highest blood levels of vitamin D127 nanomoles per liter (nmol/l)— were 50 percent less likely to have breast cancer, when compared with women with the lowest blood levels (25 nmol/l or less).


As lead author Cedric Garland elaborated in a press release from the University of California: “The data were very clear, showing that individuals in the group with the lowest blood levels had the highest rates of breast cancer, and the breast cancer rates dropped as the blood levels of vitamin D increased” (UCalSanDiego, 2/7/2007).


Dr. Garland’s team noted that women could achieve a protective blood level (80 nmol/l) by taking two steps:

  • Consume 2000 IU or vitamin D per day.
  • Spend about 12 minutes a day in the noontime sun (longer on cloudy days), with 50 percent of their skin exposed to the sun

Vitamin D versus colon cancer

The multi-university team’s second meta-analysis, which looked for links between colorectal cancer and vitamin D status, encompassed five studies in which blood was drawn from 1,448 participants (all Caucasian).


The volunteers’ blood samples were divided into five equal groups, from the lowest blood levels of vitamin D to the highest. The people with the highest blood levels had half the incidence of colon cancer, compared with those measuring the lowest vitamin D levels.


Testing your vitamin D status

There are two forms of vitamin D: 1,25(OH)D and 25(OH)D. Researchers agree that 25(OH)D is the best measure of overall D status, and this form is the one most strongly associated with overall health.


It makes sense to have your vitamin D levels tested once a yearespecially during your region’s least sunny season.


Just be sure that the doctor orders the test for the 25(OH)D form.

And as lead author Edward Gorham said, “We project a two-thirds reduction in incidence with serum levels of 46 nanograms per milliliter [117 nmol/l], which corresponds to a daily intake of 2,000 IU of vitamin D3.”


The meta-analysis included data from the Women's Health Initiative, which found no preventive benefit from low levels of vitamin D intake. However, the new meta-analysis indicates that higher doses can do the trick.


How much D do we need?

The current recommended daily allowance set by the US government is 400 IU of vitamin D per day: a consumption level that bears no relation to needs or safety concerns, and puts many people at risk.


Vitamin D experts like Dr. Michael F. Holick of Boston Universitywho co-authored both of the new studiesbelieve the evidence shows that the minimum blood level for cancer-prevention and bone-strengthening is 80 nanomoles per liter (nmol/l), and that optimal vitamin D levels range from 115-128 nmol/l.


Vitamin D levels below 50 nmol/l may raise the risk of osteoporosis, major cancers, and autoimmune diseases like MS and rheumatoid arthritis.


This is why he and others recommended that people consume 1,000 to 2,000 IU of vitamin D daily, which is the amount need to achieve 80 nmol/l. And these researchers say that people 70 years old and older may need more than 100 nmol/l.


Yet, a third of the US population has less than 30 nmol/l of vitamin D in their blood during at least part of the year, and the average level through the four seasons is in the low 60s.


If 80 nmol/l is the minimum adequate blood level, then almost all Americans are vitamin D-deficient during at least part of the year.


How vitamin D fights cancer

Vitamin D appears to help inhibit development of cancer in two ways:

  • Vitamin D inhibits inappropriate cell division and enhances the anti-cancer actions of immune system chemicals (e.g., tumor necrosis factor, interleukins 1 and 6).
  • The active hormonal version of vitamin D is produced from circulating vitamin D by cells in organs prone to cancer (e.g., colon, breast, prostate, and skin), which means that it is able to influence the initiation and growth of cancers in these organs.

And vitamin D also helps once a cancer gets a toehold:

  • Vitamin D reduces blood vessel formation around tumors and inhibits metastasis: actions that become important once cancer develops.
  • Vitamin D enhances the efficacy of chemotherapy drugs (e.g., doxorubicin)

D3 versus D2: Getting more vitamin D, in the right form

Wild salmon, wild salmon oil, and cod liver oil are the best food sources of vitamin D by far, and these sources are also extremely low in contaminants like mercury or PCBs (See our companion article “Wild Salmon Affirmed as Top Vitamin D Source”).


There are two forms of vitamin D, and only onevitamin D3is recommended by the researchers, as it is the most biologically active form, and also the form that studies associate with preventive health benefits.


Fish contain vitamin D3, but most supplements contain vitamin D2: the form found in plants, whose characteristics make it much less useful to the body and much less effective for preventive health


In other works, it takes much less D3 to equal the health effects of a given amount of D2.


The distinction between vitamin D2 and vitamin D3 is analogous to the difference between the short-chain, plant-source omega-3 called ALAonly 5-15 percent of which the body can convert to the long-chain forms it needs (e.g., EPA and DHA)and long chain omega-3s, which are abundant only in fish and zooplankton.



Sources

  • Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. Optimal vitamin d status for colorectal cancer prevention a quantitative meta analysis. Am J Prev Med. 2007 Mar;32(3):210-6.
  • Garland CF, Gorham ED, Mohr SB, Grant WB, Giovannucci E, Lipkin M, Newmark HL, Holick MF, Garland FC. Vitamin D and prevention of breast cancer: Pooled analysis. J Steroid Biochem Mol Biol. Published on-line ahead of print; doi: 10.1016/j.jsbmb.2006.12.007.
  • Grant WB, Garland CF, Gorham ED. An estimate of cancer mortality rate reductions in Europe and the US with 1,000 IU of oral vitamin D per day. Recent Results Cancer Res. 2007;174:225-34.
  • Garland CF, Mohr SB, Gorham ED, Grant WB, Garland FC. Role of ultraviolet B irradiance and vitamin D in prevention of ovarian cancer. Am J Prev Med. 2006 Dec;31(6):512-4.
  • Mohr SB, Gorham ED, Garland CF, Grant WB, Garland FC. Are low ultraviolet B and high animal protein intake associated with risk of renal cancer? Int J Cancer. 2006 Dec 1;119(11):2705-9.
  • Garland CF, Garland FC, Gorham ED, Lipkin M, Newmark H, Mohr SB, Holick MF. The role of vitamin D in cancer prevention. Am J Public Health. 2006 Feb;96(2):252-61. Epub 2005 Dec 27. Review.
  • Holick MF. Vitamin D: its role in cancer prevention and treatment. Prog Biophys Mol Biol. 2006 Sep;92(1):49-59. Epub 2006 Mar 10. Review.
  • Feskanich D, Ma J, Fuchs CS, Kirkner GJ, Hankinson SE, Hollis BW, Giovannucci EL. Plasma vitamin D metabolites and risk of colorectal cancer in women. Cancer Epidemiol Biomarkers Prev. 2004 Sep;13(9):1502-8.
  • Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF. Vitamin D and prevention of colorectal cancer. J Steroid Biochem Mol Biol. 2005 Oct;97(1-2):179-94.
  • Garland CF, Mohr SB, Gorham ED, Grant WB, Garland FC. Role of ultraviolet B irradiance and vitamin D in prevention of ovarian cancer. Am J Prev Med. 2006 Dec;31(6):512-4.
  • Garland CF, Garland FC, Gorham ED, Lipkin M, Newmark H, Mohr SB, Holick MF. The role of vitamin D in cancer prevention. Am J Public Health. 2006 Feb;96(2):252-61. Epub 2005 Dec 27. Review.
  • UCalSanDiego, 2/7/2007. Two New Studies Back Vitamin D for Cancer Prevention. Accessed online February 20, 2007 at http://health.ucsd.edu/news/2007/2_07_Garland.htm



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