Vitamine D tegen borstkanker*
Uit twee studies blijkt weer eens het belang van goede bloedwaarden vitamine D tegen de kans op
borstkanker. Uit een Amerikaanse studie blijkt dat een donker gekleurde huid het risico op lagere bloedwaarden vitamine D flink verhoogd en dat lage bloedwaarden (< 20 g/ml) de kans op agressieve borstkanker met een factor 8 doet verhogen. Uit een Franse studie blijkt dat zowel blootstelling aan zon als aanvulling met
vitamine D de beste bescherming biedt tegen het krijgen van borstkanker. In deze studie onder ruim 67.000 vrouwen blijkt dat zij die in het zuiden van Frankrijk wonen wel de helft minder kans hebben op borstkanker dan zij die in het noorden wonen. Vrouwen die behalve
regelmatig blootgesteld waren aan de zon en ook nog eens extra vitamine D met voeding en supplementen namen hadden duidelijk de hoogste bescherming tegen borstkanker.
Vitamin D Levels Lower in African-Americans, Research Finds
African-American women had lower vitamin D levels than white women, and vitamin D deficiency was associated with a greater likelihood for aggressive breast cancer, according to data presented at the Third AACR Conference on the Science of Cancer Health Disparities.
"We know that darker skin pigmentation acts somewhat as a block to producing vitamin D when exposed to sunlight, which is the primary source of vitamin D in most people," said Susan Steck, Ph.D., M.P.H., associate professor of epidemiology at the University of South Carolina.
Steck and colleagues observed 107 women who were all diagnosed with breast cancer in the previous five years. Sixty of these women were African-American, while the remaining 47 were white.
All women donated a blood sample, and vitamin D status was determined using circulating 25 hydroxyvitamin D levels as a marker. The mean serum concentration of vitamin D was 29.8 ng/ml in white women and 19.3 ng/ml in African-American women.
Researchers defined vitamin D deficiency as a serum concentration less than 20 ng/ml, and found this to be the case in 60 percent of African-American women compared with 15 percent of white women. Serum levels were lowest among patients with triple-negative breast cancer, and aggressive disease was eight times more likely among patients with vitamin D deficiency.
Steck said the findings of this study provide a foundation for a possible prevention strategy, but further research would be required.
Breast cancer breakthrough: vitamin D in combination with sun exposure is key to prevention
Women with the lowest blood levels have the highest breast cancer risk and those dying of metastasized disease are the most vitamin D deficient of all. Scientists have theorized vitamin D has anti-cancer properties that influence cell growth, healthy cell differentiation and programmed cell death (apoptosis).
However, when researchers have looked only at levels of dietary vitamin D intake and breast cancer risk, their findings have been sometimes inconsistent. So what is going on here? Does vitamin D definitely have the potential to prevent breast malignancies or not? A large and potentially groundbreaking French study appears to have the answer: the key to breast cancer prevention may well be taking higher amounts of vitamin D through diet and supplements combined with regular, direct sunshine
exposure.
The new research, headed by Dr. Pierre Engel from INSERM (Institut National de la Sante et de la Recherche Medicale, which is France's equivalent to the National Institutes of Health in the U.S.), investigated data combined from a large, decade long study involving 67,721 post-menopausal French women. The analysis came up with clear, startling evidence that while vitamin D plays a role in reducing the risk of breast cancer, the addition of adequate sunshine exposure is the factor that substantially drops the risk even more.
The scientists found that women living in the sunniest places in the south of France, such as Provence, had only about half the risk of breast cancer of women residing in less sunny latitudes, such as Paris. Even women who had the lowest vitamin D intake but who got lots of sunshine had a 32 percent lower risk of breast cancer than their counterparts living in less sunny latitudes of France. What's more, the women who consumed the most dietary vitamin D from foods and supplements and who had regular, generous sun exposure had the most significant protection from developing breast
cancer.
In their research paper, which was just published in the journal Cancer Epidemiology Biomarkers and Prevention, the French team concluded that a minimum threshold of vitamin D obtained from both sunshine and diet "..is required to prevent breast cancer and this threshold is particularly difficult to reach in postmenopausal women at northern latitudes where quality of sunlight is too poor for adequate vitamin D production."
They also noted that the minimal intake of vitamin D to reduce the risk of breast cancer is likely to vary with an individual woman's ability to metabolize or synthesize the vitamin from both diet and sunshine exposure. Adding that the average American and French woman has relative low levels of vitamin D and tends to get little exposure to sunshine, the scientists recommended "...an increase in overall vitamin D intake should be encouraged by food and health agencies."
(April 2011)
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