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Vitamin D and Breast & Endometrial Cancer
A May 2008 Canadian study found that breast cancer patients with low levels of vitamin D are much more likely to die of the disease or have it spread than patients getting enough of the nutrient - adding to evidence the "sunshine vitamin" has anti-cancer benefits. This is additional evidence about the importance of the role of vitamin D in cancer prevention.
The skin makes vitamin D from sun light. Too much sunlight can raise the risk of skin cancer, but small amounts - 20 minutes or so a few times a week without sunscreen - is beneficial plus taking Vitamin D supplements.
Researchers show that the lower the levels of vitamin D in a woman’s blood-stream, the greater the risk of her developing breast cancer if she has passed the menopause, according to research at Creighton University in Nebraska.
Of more than 1,000 women who took part in a trial, those who were given both calcium and vitamin D supplements had less than half the chance of developing breast cancer than those given a placebo (13 cases among 446 women compared with 20 cases among 288 women.
Women who stay out of the sun are increasing their risk of developing breast cancer. The safe-tanning messages that are drummed into women each year may help to reduce their risk of skin cancer – but at the cost of increasing their risk of breast and endometrial cancer.
The majority of vitamin D comes from exposure of the skin to sunlight but many women – exposed less in winter and reluctant to bare themselves in summer because of the dangers – are deficient.
There has been anecdotal evidence to suggest that breast cancer is less common among women who live closer to the Equator, where the sunshine is stronger.
Researchers enrolled 1,179 women all 55 or older, who had no history of cancer. The women were divided randomly into groups and given either supplements of calcium alone, calcium plus vitamin D, or a placebo for four years. They were interested primarily in the risk of the women suffering from osteoporosis, but they also looked at cancer risks. The study, published in the American Journal of Clinical Nutrition, found that calcium alone also had a protective effect against cancer but it was not as strong.
When the researchers repeated the analysis for those women who were free of cancer after the first year of the study, the results were even more striking. By doing this, the team excluded any cases that would have been present, but undetected, before the trial began.
In this second analysis, the risks were reduced by more than three quarters.
“Our findings of decreased all-cancer risk with improved vitamin D status are consistent with a large and still growing body of epidemiologic and observational data showing that cancer risk, cancer mortality, or both are inversely associated with solar exposure, vitamin D status, or both,” the researchers said. The findings underscored the value of achieving and maintaining a high concentration of the vitamin, they added.
The Creighton University study follows one published in the May 2007 issue of Archives of Internal Medicine that reached similar conclusions. This earlier one used data from the Nurses’ Study at Harvard, which followed more than 30,000 women for up to 15 years. Their dietary intake of both calcium and vitamin D was calculated from dietary questionnaires. The team, from Brigham and Women’s Hospital and Harvard Medical School, found that high levels of the two nutrients were linked with a 40 per cent lower risk of breast cancer in younger women.
The difference was more marked for aggressive cancers. But this study, unlike the Creighton trial, did not find a link among older women. "Findings from this study suggest that higher intakes of calcium and vitamin D may be associated with a lower risk of developing premenopausal breast cancer,” the authors concluded.
Women in the sunniest countries seem to get endometrial cancer less often than those who live far from the equator.
Using a large WHO database, researchers have found lower rates of the cancer, which strikes the lining of the uterus, in populations with a higher exposure to UVB radiation, the ultraviolet light that causes the skin to produce vitamin D, according to the November 2007 issue of Preventive Medicine.
The researchers believe that vitamin D accounts for the finding, since the geographic distribution corresponds to that of other cancers which have been shown in studies of individuals to be related to levels of vitamin D.
Vitamin D is present in foods including milk, eggs, oily fish, green vegetables and fortified margarines. But a significant part of the vitamin D need is manufactured in the skin by exposure to sunlight.
Earlier studies have linked high levels of vitamin D to reduced risks of other cancers, including of the colon and prostate. But the advice of Cancer Research UK has long been that the risk of skin cancer from overexposure to the sun exceeds benefits achieved through higher vitamin D status.
Not all experts agree. Cedric Garland, of the University of California at San Diego, claimed in the British Medical Journal in 2003 that sun avoidance would increase the risk of cancers overall, especially among those who live in northern latitudes. He recommended 10-15 minutes a day of sun exposure, without sunscreen, to allow adequate synthesis of vitamin D. But this alone is not enough, he suggested, because vitamin D is not stored for long in the body and there is not enough sun during the winter to synthesize it.
He therefore recommends the use of supplements, as in the new trial, to boost levels of vitamin D.
Vitamin D is found principally in oily fish such as salmon, tuna, sardines and herring. Supplements are also a popular source. Foods rich in calcium include milk, yogurt, dark green vegetables such as broccoli and okra, along with tofu and almonds.
Researchers said that those who had high intake of vitamin D and calcium also appeared healthier over all: they were leaner, more physically active and consumed less fat. While most cases of breast cancer develop after menopause, pre-menopausal breast cancer is often more aggressive and deadly.
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Low vitamin D levels linked to poor physical performance
Older people with low levels of vitamin D may be at increased risk for poor physical performance and disability, according to a study released in April 2007.
With a growing older population, we need to identify better ways to reduce the risk of disability. The study showed a significant relationship between low vitamin D levels in older adults and poorer physical performance.
Calls for raising the recommended daily allowance of the vitamin have been growing after reports that higher intakes could protect against osteoporosis and certain cancers.
The study analyzed data from the InCHIANTI study, involving 976 people (average age 74.8) from two towns in the Chianti area of Italy.
Participants completed a short physical performance test of their walking speed, ability to stand from a chair and ability to maintain their balance in progressively more challenging positions. Additionally, their handgrip strength was also measured.
The researchers report that low levels of vitamin D were associated with five to 10 percent lower scores of physical performance and grip strength.
Vitamin D plays an important role in muscle function, so it is plausible that low levels of the vitamin could result in lower muscle strength and physical performance. It's also possible that those with poor physical performance had less exposure to sunlight resulting in low vitamin D levels.
Current recommendations call for people from age 50 to 69 to get 400 international units (IUs) of vitamin D per day and for those over age 70 to get 600 IUs. Many researchers, however, suggest that higher amounts may be needed.
Higher amounts of vitamin D may be needed for the preservation of muscle strength and physical function as well as other conditions such as cancer prevention. The current recommendations are based primarily on vitamin D's effects on bone health.
Calls to increase vitamin D intake have been growing. Indeed, only recently fifteen experts from universities, research institutes, and university hospitals around the world called for international agencies to "reassess as a matter of high priority" dietary recommendations for vitamin D because current advice is outdated and puts the public at risk of deficiency (The American Journal of Clinical Nutrition, Vol. 85, pp. 860-868).
A recent review of the science reported that the tolerable upper intake level for oral vitamin D3 should be increased five-fold, from the current tolerable upper intake level (UL) in Europe and the US of 2000 International Units (IU), equivalent to 50 micrograms per day, to 10,000 IU (250 micrograms per day).
Recent findings showing the importance of vitamin D status on multiple health outcomes underscore the need for more research on the effects of low vitamin D levels in elderly populations.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive. The latter is derived from plants and only enters the body via the diet.
Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
Source: Journal of Gerontology: Medical Sciences
April 2007
Authors: D. Houston, G. Schwartz, S. Kritchevsky, M. Cesari, L. Ferrucci, D. Maggio, A. Cherubini, M.A. Johnson, B. Bartali
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