Rowan T. Chlebowski, M.D., Ph.D., of the Los Angeles Biomedical Research Institute at the Harbor-University of California, Los Angeles Medical Center in Torrance, Calif., and his colleagues set out to determine whether a low-fat diet could prolong relapse-free survival in women with early-stage breast cancer.
Between February 1994 and January 2001, 2,437 women who had been treated for early-stage breast cancer were recruited from the Women’s Intervention Nutrition Study (WINS). They were randomly assigned to a dietary intervention group (40%), or a control group (60%).
At the beginning of the study, both groups consumed similar amounts of calories from fat—56 to 57 grams of fat per day (about 30% of total calories). After 1 year, the women in the dietary intervention group were consuming an average of 33 g/day (20.3% of total calories) compared with 51 g/day (29.2% of total calories) in the control group. The difference between the two groups was maintained throughout the trial. Average body weight was similar before the trial started, but 5 years later, the women in the intervention group weighed an average of 6 pounds less than the women in the control group.
So the women in the intervention group ate less food total and less calories total. How much of their reduction in fats consumed came as a reduction in animal fats?
The odds of recurrence of breast cancer was low in both groups because they were caught at an early stage.
Ninety-six of 975 women (9.8%) in the intervention group had some form of relapse, compared with 181 of 1462 women (12.4%) in the control group. The researchers calculate that 38 women would need to adopt such a dietary fat reduction plan to prevent one breast cancer recurrence. "Women in the dietary intervention group had a 24% lower risk of relapse than those in the control group," the authors write.
Their data also suggest that women with hormone receptor–negative breast cancers may have had the most benefit from the dietary fat reduction, but those results weren’t statistically significant and will require further confirmation. The authors plan to address these and other questions in ongoing follow-up studies of the women.
The reduction in calories consumed might have been the real cause of the difference. Or maybe something else about the difference in diets caused the difference in risks.
They caution that the study relied on self-reports of dietary fat intake. Also, the reduction in body weight in the dietary intervention group may have had an effect on breast cancer recurrence, rather than dietary fat intake on its own.
What I'd like to know: Is the risk reduction due to lower total calories consumed? Or perhaps due to a reduction in saturated fats? In other words, do all fats put women at equal risk of recurrence or perhaps does a particular saturated fat increarse the risk of recurrence? Or did the reduction of fatty foods in the diet increase the consumption of vegetables and fruits that have compounds that reduce breast cancer recurrence?
A diet that reduces the amount of fat in it also reduces and increases the amounts of many other things. Therefore even if the women on the lower fat diet had a real reduction in their risk of recurrence of breast cancer that does not begin to tell us why.
If the women on the lower fat diets ate more vegetables then compounds in the vegetables might have reduced the rate of breast cancer recurrence. Compounds in cruciferous vegetables called isothiocyanates (ITCs) have anti-cancer effects.
"The contribution of diet and nutrition to cancer risk, prevention and treatment have been a major focus of research in recent years because certain nutrients in vegetables and dietary agents appear to protect the body against diseases such as cancer," said Shivendra Singh, PhD, lead investigator and professor of pharmacology and urology at the University of Pittsburgh School of Medicine. "From epidemiologic data, we know that increased consumption of vegetables reduces the risk for certain types of cancer, but now we are beginning to understand the mechanisms by which certain edible vegetables like broccoli help our bodies fight cancer and other diseases."
Dr. Singh's study is based on phytochemicals found in several cruciferous vegetables called isothiocyanates (ITCs), which are generated when vegetables are either cut or chewed. His laboratory has found that phenethyl-ITC, or PEITC, is highly effective in suppressing the growth of human prostate cancer cells at concentrations achievable through dietary intake of cruciferous vegetables.
In seeking to further define the mechanisms by which PEITC induces apoptosis, or programmed cell death, mice were grafted with human prostate tumors and orally administered a small amount of PEITC daily. After 31 days of treatment, the average tumor volume in the control group that did not receive PEITC was 1.9 times higher than that of the treatment group. In addition, a pro-apoptotic protein called Bax appeared to play a role in bringing about apoptosis by PEITC.
While digging for the information to write this post I felt compelled to make and eat a big bowl of cole slaw made with non-fat mayo and some canola oil. An analogue of cruciferous vegetable compound sulfurophane also has anti-cancer effects.
It is pretty easy to make a scientifically informed argument for eating a lot more fruits and vegetables. In particular, for reduction of cancer risk cruciferous vegetables such as kale, broccoli, cabbage, and arugula have compounds in them that have anti-cancer properties. The relative value of fat avoidance is harder to discern. The various fatty acids vary considerably in their metabolic roles and the generally bad reputation given to fat is too broad. Most people need more omega 3 fatty acids, not less. Also, it is not clear to me that a diet high in monounsaturated fats is a net harm.
|Share |||Randall Parker, 2006 December 17 01:26 PM Aging Diet Cancer Studies|