Macrobiotic Diet Reduces Risk of Breast Cancer

By Alex Jack

In a random case control study involving 104 middle-aged women, Italian researchers reported this year that a macrobiotic diet could substantially reduce hormonal levels associated with higher risk of breast cancer. Known as the DIANA (Diet and Androgens) Trial, the study was conducted by the National Tumor Institute in Milan, funded by Cancer Program of the European Union, the Italian Association for Research on Cancer, and the CARLIPO Foundation, and published in Cancer Epidemiology, Biomarkers & Prevention, a major research journal in the United States.

The post-menopausal women were selected from a pool of volunteers living in the Milan area in north Italy who were at high risk for breast cancer on the basis of their hormonal and metabolic values. Half were assigned to the control group and half to the intervention group that received intensive dietary instruction and ate together twice a week over 4 1/2 months.

The researchers cited accumulating medical evidence that modern dietary habits, especially foods that contribute to hormonal imbalance, raise the risk of breast cancer, an epidemic disease that will afflict one in every eight women in America and Europe. Among Asian women who regularly consume soy products and other traditional foods, the rates of breast cancer are substantially lower than in Western women. However, the efficacy of dietary changes in reducing the availability of sex hormones in high risk women had not been sufficiently investigated.

The women in the study, aged 50 to 65 years, had testosterone levels that were two-thirds or more higher than average and hence put them at elevated risk for breast cancer. All had been postmenopausal for at least 2 years, had at least one ovary, had not taken hormonal replacement therapy for at least the previous 6 months, and were not diabetic. None of the women was following a vegetarian, macrobiotic, or other medically prescribed diet. The 52 women in the control group were not given any information about the diet but were advised to increase their consumption of fruit and vegetables according to the cancer prevention guidelines of the European cancer program, a leaflet available to the public.

The 52 women in the intervention group attended macrobiotic cooking classes twice a week for 18 weeks and were encouraged to cook and eat macrobiotically at home, especially one soy product daily such as miso soup, tofu, or tempeh. Every week, the women received whole grains and other products donated by local natural foods manufacturers. During the first month, the women were advised to make dietary changes gradually, but later no advice was given to reduce total food intake or to count calories.

Prior to the trial, both groups of women received about 37% of calories from fat (mainly meat, dairy, and olive oil) and 42% from carbohydrate (bread and pasta). The intervention group shifted from animal to vegetable sources, reducing their meat consumption from daily to 1-2 times a week, dairy was halved, and butter virtually eliminated. Soy products were consumed on average 1.7 times daily and sea vegetables used every other day. Brown rice and other whole grains were consumed 2.5 times per day compared to 0.5 times by controls, and intake of legumes, cruciferous vegetables, and berries were 4-8 times higher.

Total cholesterol decreased from 240 to 206 mg/dl compared to 230 in the control group. The intervention group lost more weight, 4.06 kg compared to 0.54 kg, and underwent statistically significant improvements in the five major hormonal and metabolic values associated with breast cancer risk: sex hormone-binding globulin, testosterone, estradiol, fasting insulin, and fasting glycemia. Serum sex hormone-binding globulin levels increased 25.2%, while testosterone and estradiol decreased 19.5% and 18%.

"We observed significant and favorable changes in hormonal indicators of breast cancer risk in a group of postmenopausal women living in northern Italy," the researchers concluded. "These results suggest that the multifactorial dietary intervention applied in this study may prevent breast cancer if continued in the long term." "Compared with the usual Western microflora, the gut of macrobiotic or vegetarian subjects may be richer in lactobacilli and bifidobacteria," the scientists further noted.

Compared to previous studies that involved a single factor, the DIANA trial involved a multifactorial approach that produced stronger results. "We suggest that these favorable changes are to be attributed to the cumulative effects of a comprehensive dietary strategy that combines lowered total fat intake, lowered proportion of saturated fatty acids, and lowered consumption of high-glycemic-index foods with increased intake of dietary fibers from cereals, legumes, and vegetables, and a high cumulative dose of diverse phytoestrogens from various food sources."

Source: Franco Berrino et al., "Reducing Bioavailable Sex Hormones through a Comprehensive Change in Diet: the Diet and Androgens (DIANA) Randomized Trial," Cancer Epidemiology, Biomarkers, & Prevention 10: 25-33, January 2001.

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