Diet and breast cancer in Shanghai and Tianjin, China

Abstract

Suimary Various aspects of adult diet have been linked to breast cancer development. These include intake of fat (risk factor), and intake of fibre, soy protein and vitamins A, C and E (protective factors). Results of previous studies have been inconsistent. We examined the possible associations between breast cancer and various indices of nutrient and food intake in two Chinese populations who are at relatively low risk for breast cancer (one-fifth the rate in US white women). Two case-control studies of breast cancer were conducted in the cities of Shanghai and Tianjin, China. In Shanghai, 534 women aged 20-69 years with histologically confirmed breast cancer were recruited, whereas in Tianjin 300 women aged 20-55 years with histologically confirmed breast cancer were interviewed. All controls were community controls who were individually matched to the cases by sex and age (case-control ratio= 1:1). All interviews were conducted in person. Findings from the two studies were similar, although the diets in Shanghai and Tianjin were different in many respects. Cases and controls were similar in their consumption of soy protein, measured either in absolute levels or as percentages of total protein. Overall, all components of dietary fat (saturated fat, monounsaturated fat. polyunsaturated fat) showed a modest, non-significant association with breast cancer after adjustment for energy intake and other non-dietary risk factors for breast cancer. Intake of crude fibre, carotene and vitamin C. on the other hand, exhibited strong, statistically significant inverse associations with breast cancer risk. The last three indices were highly correlated, rendering it impossible to disentangle their individual effects; they were closely associated with intake of green vegetables in the two study populations. Vitamin E intake was unrelated to breast cancer risk in Shanghai and Tianjin. In the multivariate logistic regression model which included all non-dietary risk factors for breast cancer and energy intake, Shanghai women in the lowest tertile of crude fibre intake and highest tertile of fat intake had a 2.9-fold increased risk for breast cancer relative to those in the highest tertile of crude fibre intake and lowest tertile of fat intake. The comparable relative risk in Tianjin women was 2.4. Our data indicate a strong protective effect against breast cancer development with intake of foods rich in fibre, vitamin C and carotene. Our results are also compatible with dietary fat having a modest, positive effect on breast cancer risk within the range of exposure experienced by women in China. Our study does not support the hypothesis that high intake of soy protein protects against breast cancer.

Lifelong vegetarianism and risk of breast cancer: A population‐based case‐control study among South Asian migrant women living in England

“…The inverse trend between NSP intake (a marker of fruit and vegetable consumption) and the odds of breast cancer observed in the present study is also consistent with that from a meta-analysis of case-control studies, 35 which reported a weak, but statistically significant, protective association. Several recent studies, not included in the meta-analysis, have found similar statistically significant protective associations with various components of fibre, 36 -38 crude fibre 39 and fibre from vegetables and fruit, but not cereals. 40 No association between total dietary fibre intake and subsequent incidence of breast cancer was reported by 2 prospective studies conducted in the US, 41,42 but a weak protective effect was found in a prospective study conducted in Canada.…”

Vitamins C and E, retinol, beta-carotene and dietary fibre in relation to breast cancer risk: a prospective cohort study

“…In other epidemiological studies, there was some evidence for an inverse association between consumption of vegetables and fruit and risk of breast cancer, although this was not very consistent (reviewed by Steinmetz and Potter, 1991). Yuan (1995) Per unit intake 0.9 (per 1753 IU) 0.6a,b (per 7269 IU) 0.3b (per 179 mg) 0.7 (per 30 mg) 0.4b (per 6 g) Freudenheim (1996) Highest vs lowest quartile 0.46b 0.53b 0.55b 0.52b alntake of carotene. b Significant association.…”

Epidemiology of soy exposures and breast cancer risk

“…Specifically, two studies (Wu et al, 1996;Ho et al, 2006) examined only about intake of tofu. Four other studies (Yuan et al, 1995;Key et al, 1999;Hirose et al, 2003;Nishio et al, 2007) asked about intake of several soy foods that captured between 40 and 60% of total soy intake in those populations.…”

“…We also examined the results of the six excluded studies (due to incomplete soy assessment) (Yuan et al, 1995;Wu et al, 1996;Key (2007). We calculated ORs associated with soy products (in g) for pre-and postmenopausal women combined in the study by Lee et al (1991); the results in postmenopausal women in this study were published in a 1992 paper.…”