Although elevated cholesterol levels are most closely associated with heart disease, there is also evidence that they could raise risk for breast cancer. According to researchers from Duke University Medical School and several other institutions, a metabolite of cholesterol called 27HC turns into a potent estrogen-like molecule that could affect risk of breast cancer. Therefore, it is possible that approaches to lowering blood cholesterol may help to prevent and treat breast cancer. Consuming more soyfoods may be one of those effective approaches.
Links between elevated cholesterol and breast cancer risk have been made before. For example, it has been known that disease-free survival is improved in breast cancer patients who are taking statins, which are cholesterol-lowering drugs, before diagnosis. New research in rodents provides some clues about why this may be.
The study showed that 27HC, just like the hormone estrogen, stimulates the growth of existing breast tumors. Furthermore, it was shown that in human breast cancer specimens, levels of the enzyme responsible for producing 27HC from cholesterol were correlated with tumor grade. That is, the enzyme levels were highest with tumors that were more aggressive and deadly.
As a result of their findings, the investigators concluded that lowering circulating cholesterol levels or interfering with the conversion of cholesterol to 27HC may be a useful strategy to prevent and/or treat breast cancer.
Soyfoods may be useful in this regard because they lower cholesterol in two important ways. First, because they are high in polyunsaturated fat, they help to lower blood cholesterol levels when they replace protein-rich animal foods, which are high in saturated fat. Second, the protein in soyfoods directly lowers blood cholesterol levels. The ability of soy protein to lower cholesterol levels was formally acknowledged by the FDA in 1999 when it allowed a health claim for soyfoods and coronary heart disease.
University of Toronto researchers estimated that as a result of these two mechanisms, soyfoods have the potential to lower blood cholesterol levels by as much as eight percent. While it isn’t certain that the lowered levels will reduce breast cancer risk, that eight percent reduction is estimated to lower risk of heart disease by eight to 16 percent.