By Karen Collins, RD

The effect of dietary fat on breast cancer recurrence is not clear, but at least for now, the best advice seems to include limiting fat consumption to reduce risk of the cancer returning.

Yet, how a low-fat diet is put into practice may influence its benefits.

In the Women's Intervention Nutrition Study, researchers evaluated more than 2,400 post-menopausal women with early-stage breast cancer who were being treated by usual methods.

Forty percent of the women were assigned to a program of intensive nutrition counseling to lower fat consumption. The rest, a "comparison" group, received modest information about meeting nutritional needs.

Both groups began by eating about 56 grams of fat a day, about 30 percent of their calories. A year later, the low-fat diet group averaged 33 grams of fat a day; the comparison group averaged 51 grams.

After five years, the low-fat diet group had 24 percent less recurrence of breast cancer than women in the comparison group. The risk of cancerous tumors fueled by estrogen dropped only slightly, but the risk of non-estrogen breast cancer was 42 percent less in the low-fat group.

Reducing estrogen 

The difference between the two groups was somewhat surprising because research has suggested that part of a low-fat diet's protection against breast cancer involves reducing estrogen levels.

This study fits with work suggesting that reduced fat intake can lower levels of other apparent promoters of breast cancer, such as insulin and insulin-like growth factors. 

However, you can use many strategies to cut fat in your diet, and all may not have the same effect.

For example, a small number of women in the nutrition study's low-fat group who met fat targets chose lower-fat versions of cheese, meat, poultry, salad dressing and sweets. The biggest difference between those women who met their low-fat goals and those who didn't, however, was what they ate: less high-fat muffins, cookies, snack foods, cheese, eggs and red meat.

The type of fat you cut may also be significant. Some studies have found saturated fat in meats and dairy products most likely will raise insulin levels and promote inflammation. In the women's nutrition study, the low-fat group reduced saturated fat from about 19 grams a day to about 10 grams.

But in the Women's Health Initiative, a study examining whether decreasing dietary fat could reduce initial cases of breast cancer, a lower-fat group enjoyed a nine-percent less incidence of cancer, which was not statistically significant.

Role of weight loss

Part of a low-fat diet's protection against breast cancer could stem from weight loss. During a follow-up of almost 15 years among 4,000 pre- and post-menopausal women with breast cancer, women who suffered from obesity were 34 percent more likely to die of breast cancer than lean women.

In the Women's Intervention Nutrition Study, the low-fat diet group lost about between four and five pounds after one year and maintained their loss throughout the study. We don't know if their reduced cancer recurrence was helped by even this small weight loss or if the diet itself provided most of the benefit.

Another possible protective effect of a low-fat diet is connected with eating more foods with naturally occurring, disease-fighting compounds called phytochemicals - foods like vegetables, fruits, whole grains and beans.

Reducing fat consumption should be just one part of a strategy for protection from breast cancer. Research now links physical activity with lower risk of initial occurrence of breast cancer and also seems to support activity's link with reduced risk of recurrence.

All these changes need to be part of a healthful lifestyle, not a temporary fix.

Role of physical activity

Speaking of physical activity, a new study shows that engaging in six or more hours a week of strenuous recreational exercise may reduce your risk of invasive breast cancer by 23 percent, according to the American Association for Cancer Research.

Invasive cancer has spread outside the milk duct or milk-making glands and into normal tissue inside the breast. Whether a woman's cancer is invasive will determine her treatment choices and how she might respond to them.

The findings from the study of 15,000 women by  University of Wisconsin cancer experts show that the risk reduction came whether women exercised early in life or after menopause. Generally, postmenopausal women who are physically active have lower levels of estrogen, which may explain their reduced risk, the researchers said. 

"A woman's hormone levels naturally fluctuate throughout her life, and we have found that exercise likely offers protection against breast cancer regardless of a woman's stage in life," said Brian Sprague, the study's lead author. "The take-home message for women should be that it is never too late to begin exercising."

Most of this article was written by Karen Collins, a registered dietitian whose work appears on  Nubella News, MSNBC.com and in newspapers throughout the country. She is nutrition adviser to the American Institute for Cancer Research in Washington, D.C.

Collins' organization is not affiliated with the Philadelphia-based American Association for Cancer Research.

Source: American Institute for Cancer Research/American Association for Cancer Research
Reference: Nutrition Notes/Cancer Epidemiology Biomarkers & Prevention

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