ETIOLOGIC STUDIES OF DIET AND CANCER

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The Nutritional Epidemiology Branch conducts research on the role of diet and nutritional status in cancer etiology. The majority of research is focused on observational studies, both case-control and prospective. Biochemical and molecular components are commonly incorporated into these investigations and methodologic studies designed to assess and/or improve exposure assessment continue to be an active area of research. The role of nutrition is currently being evaluated in studies of lung, oral/pharyngeal, esophageal, stomach, colorectal, breast, endometrial, cervical, prostate, and brain cancers; non-Hodgkin's lymphoma; and malignant melanoma. Major research efforts continue to focus on the role of 1) diet, body size, endogenous hormones, and lifestyle including alcohol consumption, smoking, and physical activity; 2) vegetables, fruits, micronutrients, carotenoids, and phytochemicals; 3) food preparation practices; and 4) diet-gene interactions. Recent findings include the following: 1) In a large case-control study of breast cancer in Asian-American women, frequent intake of soy products rich in phytoestrogens was found to be protective; 2) In a nested case-control analysis of stored sera from the Honolulu Heart Program cohort, low serum levels of alpha-carotene, beta-carotene, beta-cryptoxanthin, and lycopene were associated with increased lung cancer risk, and risk of oral-pharyngeal, esophageal, and laryngeal cancer was elevated for low levels of alpha-carotene, beta-carotene, and beta-cryptoxanthin; 3) Increased consumption of heterocyclic aromatic amines (HCAs), found in meat products cooked at high temperatures have been linked to increase risk of colorectal adenomas, adenocarcinoma of the stomach and esophagus, and lung cancer; 4) In a study of breast cancer among young women in the U.S., breast cancer risk was lower among heavy compared with thin women. High compared with low body mass index was also related to lower circulating estrogen concentrations. In the same study, alcohol intake was directly associated with risk of the disease; 5) Post-diagnostic influences on dietary assessment were evaluated in a case-control study of young women. Cases on chemotherapy reported higher intake of calories and all energy providing nutrients compared with controls, whereas cases of similar stage not receiving this treatment did not show this effect, suggesting that chemotherapy itself was related to altered reporting of usual dietary intake; 6) In an evaluation of the influence of early-life exposures on subsequent breast cancer risk, having been a twin was associated with increased risk, while having been breast-fed as an infant was associated with lower risk of the disease; 7) In a retrospective study, endometrial cancer associated with obesity was shown not to be mediated through either the elevated estrogen concentrations or increased insulin secretion associated with obesity.