| In this first issue of Abreast and the Rest, we've turned our attention to cancer affecting women. A simple but important message is that all women can benefit from eating well and maintaining a healthy body weight. While one size doesn't necessarily fit all, the early evidence does suggest that there are likely to be more similarities than differences when it comes to diet and cancer prevention in women. At present the majority of studies have focused on breast cancer but it appears that what is recommended for breast cancer can also be encouraged for other types of cancer that affect women. That is, in some cases, the same factors that increase or decrease the risk of breast cancer also affect the risk of other cancers diagnosed in women.
The evidence comes from an expert report from the American Institute for Cancer Research1, which is recognized as the most comprehensive summary on diet and cancer available today. This report examined the effect of diet on the risk of developing cancer including breast cancer and cancer of the endometrium (uterus), cervix and ovary. Several diet and lifestyle factors were reported to be related to the risk of developing breast cancer.
Evidence suggests that the risk of breast cancer is lowered by physical activity and increased by alcohol consumption and a number of factors associated with body weight. This includes body as well as body fatness, abdominal fatness and adult weight gain. Other cancers that affect women share these same risk factors. For example, the risk of endometrial cancer is also decreased by physical activity and increased by body fatness and abdominal fatness. For other less common cancers of the cervix and ovary there is limited research available to determine what effect these factors have on cancer risk. Where there is data, the evidence is often too low in quality, too inconsistent or the number of studies is too few to allow conclusions to be reached1.
Diet and lifestyle factors are known to affect the risk of cancer in women in part by their relationship to hormones and reproductive factors. It is well established that estrogen (commonly known as a hormone), along with reproductive factors, are related to the development cancer in women. Cancer of the breast, ovary, endometrium and cervix are included in these types and as such are often referred to as hormone sensitive cancers.
|Modifiable Factors Associated with|
Cancer Risk in Women:
|LEVEL OF EVIDENCE||FACTORS INCREASING|
|TYPE OF CANCER|
|CONVINCING||Body fatness||Endometrial Cancer|
|Alcoholic Drinks||Breast Cancer|
|PROBABLE||Abdominal fatness||Endometrial Cancer|
|Adult Weight Gain||Breast Cancer|
Excess body weight and body fatness and to some degree the amount of fat consumed in the diet can directly affect many of the circulating hormones such as estrogen, insulin and insulin-like growth factors. This can create an environment that over time encourages cancer development and inhibits the body's mechanisms against cancer. It can also stimulate the body's inflammatory response, which can contribute to the initiation and progression of several cancers1.
While most of the estrogen produced in a women's body is made in the ovaries, fat cells are also able to produce estrogen by converting other hormones into estrogen. Collectively, these factors help to explain why in comparison with women who maintain a healthy weight, cancer risk is higher in overweight and obese women. In the example of endometrial cancer, cancer is twice as common in overweight women, and more than three times as common in obese women2.
Keeping perspective is important and in fact, the benefits of lifestyle factors go well beyond cancer and also contribute to vitality and well-being and protect against many common conditions such as diabetes and heart disease.
1. Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective (2007), American Institute for Cancer Research (www.aicr.org)
2. Detailed Guide: Endometrial Cancer. What are the Risk Factors for Endometrial Cancer? American Cancer Society website (as viewed December 10, 2009) http://www.cancer.org