High intake of milk may raise ovarian cancer risk
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Could a lot of dairy be too much of a good thing? An analysis of 21 studies that investigated ties between ovarian cancer and the consumption of milk products and lactose provides some support for the notion that a high intake is associated with increased ovarian cancer risk.
“The important observation,” said Dr. Susanna C. Larsson, “is that a high intake of milk and milk sugar (lactose) was associated with increased risk of ovarian cancerr in prospective studies (in which diet has been assessed before the cancer diagnosis) but not in case-control studies (in which diet has been assessed after the cancer diagnosis.”
Milk and milk products are rich in a number of nutrients, Larsson noted. However, lactose (milk sugar) might be the factor in milk that possibly increases the risk of ovarian cancer. “Perhaps lactose-free milk is safe,” she suggested. “I wasn’t really surprised of the findings because there is biologically plausibility that milk sugar may be a risk factor for ovarian cancer.”
In the International Journal of Cancer, Larsson and colleagues from the Karolinska Institute in Stockholm point out that studies that examined the association between lactose and dairy food consumption and ovarian cancer risk have yielded conflicting results. The researchers therefore summarized the available literature on this topic.
The findings of 18 case-control studies differed, the team reports, “and, except for whole milk, do not provide evidence of positive associations between dairy food and lactose intakes with risk of ovarian cancer.”
In contrast, the three prospective cohort studies were “consistent” and show significant positive associations between intakes of total dairy foods, low-fat milk, and lactose and risk of ovarian cancer.
What is going on in the body?
The ovaries are inside the woman’s pelvic area. From puberty to menopause, the ovaries produce female hormones. These hormones regulate the menstrual cycle, or menstruation. The ovary also contains eggs. The female hormones regulate the release of eggs during the cycle.
When an ovarian cell becomes cancerous, it will begin multiplying rapidly. A growth, or tumor, on the ovary forms as the cells multiply. This growth may or may not interfere with the function of the ovary. Cancer cells can break off from the tumor and spread directly to other areas inside the pelvis. Cancer cells can also metastasize through the bloodstream to other areas of the body.
For a daily increase of 10 grams in lactose intake—the approximate amount in one glass of milk—the risk of ovarian cancer increases by 13 percent, the team calculates.
“Although milk consumption might increase the risk of ovarian cancer, consumption of milk has other potential benefits,” Larsson said.
“For instance, there is strong evidence that high consumption of milk may reduce the risk of colorectal cancer. There is also limited evidence that consumption of low-fat dairy foods may lower the risk of other diseases such as cardiovascular disease and type 2 diabetes. Thus, I would not recommend women to stop drinking milk,” she said.
However, the researcher concluded, “In the future, when we know more about possible interactions between milk consumption and genetic susceptibility, it might be that some women should not drink milk because of a high risk of developing ovarian cancer.”
SOURCE: International Journal of Cancer, August 1, 2005.
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