The February, 2009 issue of the American Association for Cancer Research journal Cancer Epidemiology, Biomarkers & Prevention published the discovery of researchers from the University of California, San Diego, the University of Arizona, and other research centers of a positive effect of high carotenoid intake on recurrence-free survival in breast cancer patients. Carotenoids, such as beta-carotene, occur in most fruits and vegetables. Diets high in these plant foods have been linked with a protective effect against various cancers in a number of studies.
The current study included 3,043 participants in the Women's Healthy Eating and Living Study which was designed to evaluate the effect of a high plant food, low fat diet on breast cancer recurrence and survival in women diagnosed and treated for early-stage disease. Participants were assigned to a group that had as its goal consumption of 5 vegetable servings per day, 3 fruit servings, 30 grams fiber, and 15 to 20 percent of calories from fat, or to a group that received instructions on achieving a daily intake of 5 servings of combined vegetables and fruit, at least 20 grams of fiber, and less than 30 percent of energy intake from fat. Blood samples collected upon enrollment and at one, two or three, four and six years were analyzed for plasma carotenoids, including alpha-carotene, beta-carotene, lutein, lycopene, and beta-cryptoxanthin. Average carotenoid concentration over time, reflecting dietary intake, was estimated for each participant, and those with low, medium and high concentrations were compared.
Over the 7.12 median follow-up period, 508 cases of breast cancer occurred. Compared with women whose carotenoid levels were among the lowest one-third of participants, subjects whose levels were in the top two-thirds experienced a 33 percent lower risk of a recurrence or new primary breast cancer.
The study's results suggest that carotenoids or their metabolites could affect cancer progression, although the authors admit that other food components provided by a diet associated with higher plasma carotenoids could be responsible. "Although negative findings from the beta-carotene supplement trials have dampened the enthusiasm for the potential role of carotenoids in chemoprevention, laboratory evidence relating to the possibility of a specific role for dietary carotenoids in reducing the risk and progression of breast cancer continues to be very supportive," they note.
"Higher biological exposure to carotenoids, when assessed over the time frame of the study, was associated with greater likelihood of breast cancer–free survival regardless of study group assignment," the authors conclude. "These results suggest that longer-term exposure to a high vegetable and fruit dietary pattern that promotes higher plasma carotenoid concentration may improve prognosis and survival."
Related Health Concern: Breast cancer
A wide variety of factors may influence an individual's likelihood of developing breast cancer; these factors are referred to as risk factors. The established risk factors for breast cancer include: female gender, age, previous breast cancer, benign breast disease, hereditary factors (family history of breast cancer), early age at menarche (first menstrual period), late age at menopause, late age at first full-term pregnancy, obesity, low physical activity, use of postmenopausal hormone replacement therapy, use of oral contraceptives, exposure to low-dose ionizing radiation in midlife and exposure to high-dose ionizing radiation early in life.
Correlated risk factors for breast cancer include never having been pregnant, having only one pregnancy rather than many, not breast feeding after pregnancy, diethylstilbestrol (DES), certain dietary practices (high intake of fat and low intakes of fiber, fruits, and vegetables), tobacco, smoking, abortion, breast trauma, large breast size, synthetic estrogens, electromagnetic fields, use of nonsteroidal anti-inflammatory drugs (NSAIDs), and alcohol consumption. Alcohol is known to increase estrogen levels. Alcohol use appears to be more strongly associated with risk of lobular carcinomas and hormone receptor-positive tumors than it is with other types of breast cancer (Li et al. 2003).
A novel growth inhibitor recently identified as estrogen down-regulated gene 1 (EDG1) was found to be switched off (down-regulated) by estrogens. Inhibiting EDG1 expression in breast cells resulted in increased breast cell growth, whereas over-expression of EDG1 protein in breast cells resulted in decreased cell growth and decreased anchorage-independent growth, supporting the role of EDG1 in breast cancer (Wittmann et al. 2003).
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