The current study was designed to examine the association between adolescent fiber intake and proliferative benign breast disease, an indicator of increased breast cancer risk. The study included 29,480 women in the Nurses’ Health Study II who completed a high school diet questionnaire in 1998. A centralized pathology review was used to identify 682 proliferative benign breast disease cases in this group between 1991 and 2001. Multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using multivariate-adjusted Cox proportional hazards regression. Women in the highest fifth of adolescent fiber intake were found to have a 25% lower risk of proliferative benign breast disease than women in the lowest quintile (HR = 0.75, 95% CI = 0.59 - 0.96, p-trend = 0.01). High school intake of nuts was also found to be associated with significantly reduced risk of benign breast disease. Women consuming at least two servings of nuts per week had a 36% lower risk than women consuming fewer than one serving per month (HR = 0.64, 95% CI = 0.48 - 0.85, p-trend < 0.01). The results held when the analysis was restricted to the 142 prospective cases who had been diagnosed after having completed the high school diet questionnaire. The authors conclude that dietary intake of fiber and nuts during adolescence influences subsequent risk of benign breast disease and may be a means to prevent breast cancer.

The present study was designed to determine the optimal dietary omega-6 to omega-3 (n-6/n-3) fatty acid ratio for breast cancer prevention in an animal model. Although consumption of omega-3 fatty acids has been reported to be beneficial in preventing breast cancer, the optimal n-6/n-3 ratio has not been established. Both n-6 and n-3 fatty acids are essential for normal development and biological functioning. However, both also have metabolizing enzymes in common and have the potential to antagonize each other’s metabolism thereby. In the study, experiments were performed to determine the ratio or ratios of dietary n-6/n-3 that are optimal for chemoprevention while at the same time avoiding adverse effects on normal development. Mammographic density was used as a surrogate marker for breast cancer risk. Groups of nine 32-day old female Sprague Dawley rats were randomly assigned to one of seven dietary regimens with n-6/n-3 ratios as follows: 25:1, 10:1, 5:1, 1:1, 1:5, 1:10, and 1:25. The overall proportion of calories from fat was fixed at 30% across all seven diets. Rat mammary gland density was measured using digital analyses of abdominal-inguinal mammary gland whole mounts stained with alum carmine. Density was estimated using either area or integrated optical density and reported as percentage of the mammary gland fat pad occupied by mammary epithelium. Density was found to be unaffected in the high n-6 group of the study; in other words, a high omega-6 diet did not induce any increase in density. However, mammary gland density was found to be significantly reduced in the high omega-3 group (16%, p<0.03). The authors comment that they are in the process of determining (1) whether reduced mammary gland density is accounted for by effects on the cell cycle or by induction of a pro-apoptotic environment; (2) the extent to which these effects are influenced by altered signaling via activated protein kinase B (Akt); and (3) the mechanism of action by which the n-6/n-3 ratio alters eicosanoid-mediated bioactivity.

Walnuts contain essential omega-3 fatty acids, antioxidants and phytosterols that have previously been shown to reduce the risk of breast cancer. The present study was designed to determine the impact of consuming walnuts on the risk of breast cancer. One group of laboratory mice were fed a diet containing the approximate human equivalent of two ounces of walnuts per day. A separate group were fed a control diet. Walnut consumption was shown to significantly decrease breast tumor incidence, the number of glands with tumors, and tumor size. Walnut consumption delayed the development of tumors by at least three weeks. Molecular analysis showed that increased consumption of omega-3 fatty acids contributed to the decline in tumor incidence, but other parts of the walnut contributed as well.

In the present study, nine types of tree nuts commonly available in the United States and peanuts were evaluated for total phenolic and flavonoid contents, as well as antioxidant and antiproliferative activities. Phytochemicals (especially phenolics) are considered to be the major bioactive compounds for health benefits in nuts. Frequent nut consumption has been linked to lower risk of cardiovascular disease. Total phenolics and flavonoids, including both soluble free and bound forms, were estimated. Of the nuts studied, walnuts were found to have the highest total phenolic and flavonoid contents, as well as the highest total antioxidant activity. Both soluble phenolic and flavonoid contents were found to be positively correlated with total antioxidant activity. Exposure to the extracts of nuts significantly inhibited the proliferation of HepG2 liver cancer and Caco-2 colon cancer cells in a dose-dependent manner, with walnuts and pecans having the highest antiproliferative activity.

This pilot study was performed to determine whether consumption of walnuts could affect the growth of MDA-MB 231 human breast cancers implanted into nude mice. After the tumors grew to three to five mm in diameter, the diet of one group of mice was modified to include ground walnuts, equivalent to 2 oz per day in humans. In the group that consumed walnuts, the tumor growth rate from Day 10 (when tumor sizes in the two groups began to diverge) until the end of the study of was significantly lower than that of the mice that did not consume walnuts. The eicosapentaenoic and docosahexaenoic acid fractions of the livers of the walnut-fed group were also found to be significantly higher than that of the control group. Tumor cell proliferation declined, but apoptosis was not changed due to walnut consumption.

Numerous studies have shown that consumption of long chain omega 3 fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) can retard cancer growth. Dietary phytosterols and antioxidants (e.g., vitamin E and melatonin) can also slow the growth of cancer. The present study was designed to determine the effect of consumption of walnuts on the growth of MDA-MB 231 human breast cancer tumors implanted into nude mice. One million MDA-MB 231 cells were injected subcutaneously into 40 nude mice that were consuming a diet containing 10% corn oil to promote tumor growth. After the tumors reached 3-5 mm in size, the mice were divided into two groups so that the average tumor size of each group was equal and had equal numbers of larger and smaller tumors. The diet of one group of mice was modified to include ground walnuts; each of these mice consumed the human equivalent of one ounce of walnuts per day. The diets of both groups were balanced to contain equal amounts of protein, carbohydrate, fat and fiber. The tumors were measured and the mice were weighed three times per week. At about Day 10 after the diet change, tumor sizes in the two groups began to diverge. The growth rate of tumors of the walnut diet group was found to be significantly lower than that of the control group from day 10 until the end of the study. The eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content of the liver and fat of the walnut diet group was significantly higher than that of the non-walnut group, indicating that the ALA was efficiently converted to EPA and DHA.