VITAMIN D MAY PROVIDE BREAST CANCER PREVENTIVE EFFECT

VITAMIN D MAY PROVIDE BREAST CANCER PREVENTIVE EFFECT due to the nutrient's influence on calcium absorption, Harold Newmark, MS, Memorial Sloan-Kettering Cancer Center, suggested at a Sept. 4 conference on diet and breast cancer sponsored by the American Institute for Cancer Research. Newmark speculated that higher intakes of calcium and vitamin D during adolescence could help reduce the risk of breast cancer later in life. Based on studies using rat models, Newmark hypothesized that "high dietary fat could act as a direct increasing factor for [tumor] proliferation in the mammary epithelial" area and that dietary calcium and dietary vitamin D "could possibly . . . effect this proliferation and thereby act as protective agents." Newmark suggested that the "big risk is in the development period of the mammary gland" when high dietary fat in the diet can "magnify or amplify" the hormonally driven growth of the gland. Using data based on rodent studies, Newmark showed that an increased calcium level in rats with high fat diets "markedly" reduced the rate of tumor proliferation. The addition of vitamin D into the diet, Newmark pointed out, further decreased the number of palpable tumors in the animal models. "Vitamin D is very important in not only regulating the absorption of calcium from the [gastrointestinal] tract but absorption of calcium into the cells," Newmark explained. He suggested that "absorption of calcium into the cells would be needed to counteract the toxic effects of the free fatty acids." Newmark also referred to a study that analyzed the geographic incidence of breast cancer in the U.S. According to the study, Newmark said, the breast cancer "hot spots" occurred in the areas of the country where sunlight is less intense over the course of the year or where high levels of smog may reduce the sunlight intensity. He suggested that the incidence of breast cancer is lower in areas of the country where vitamin D is attained through sun exposure as well as diet. Other speakers at the conference who discussed the possible preventive effects of vitamins included Richard Moon, PhD, University of Illinois Specialized Cancer Center. Using animal studies as his model, Moon discussed the inhibiting effect of a particular analog of vitamin A, 4-hydroxyphenyl retinamide (4HPR), on the growth of existing tumors and on their proliferation. Moon also cited an ongoing five-year breast cancer prevention trial in Milan, Italy where 2,900 women with breast cancer have been given either 4HPR or a control. Reporting preliminary data from the trial in about 200 patients, Moon noted that 26 individuals had developed tumors in the contralateral breast in the 4HPR group compared to 20 in the control group. Moon observed that "there is no difference between the two arms [of the study] at the present time." However, he suggested that any benefit from the retinoid treatment would not statistically appear until the fourth or fifth year of the study. The Milan group conducting the 4HPR study has initiated another trial to determine whether a combination of 4HPR and tamoxifen is more effective in preventing breast cancer than either tamoxifen or 4HPR given alone.