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Intakes of meat, eggs, or dairy products are not consistently linked to risks for breast cancer, according to the results of a prospective study reported ahead of print in the June 2 issue of the American Journal of Clinical Nutrition.

"Meat, eggs, and dairy products — prominent features of the Western diet — have been consistently associated with increased breast cancer incidence and mortality in ecological studies; moreover, there has been an ecological trend of increasing breast cancer mortality coincident with the increase in consumption of animal products that occurred after World War II," write Valeria Pala, from Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy, and colleagues. "The 2007 World Cancer Research Fund report concluded that observational epidemiologic studies do not consistently implicate consumption of any animal food in breast cancer risk."

Using data from the European Prospective Investigation into Cancer and Nutrition, the investigators studied the association of meat, egg, and dairy intake with breast cancer risk among 319,826 women who provided dietary information between 1992 and 2003. Multivariate Cox proportional hazard models allowed estimation of disease hazard ratios (HRs).

During median follow-up of 8.8 years, 7119 cases of breast cancer were diagnosed. There was no consistent association between the risk for breast cancer and dietary intake of any of the food groups studied, with use of either categoric or continuous exposure variable models.

In the categoric model, high intake of processed meat was linked to a small increase in breast cancer risk (HR for highest vs lowest quintile, 1.10; 95% confidence interval [CI], 1.00 - 1.20; P for trend = .07). In premenopausal women only, subgroup analyses suggested an association of breast cancer risk with butter consumption (HR for highest vs lowest quintile, 1.28; 95% CI, 1.06 - 1.53; P for trend = .21).

Findings for red meat intake (beef, veal, pork, and lamb) were heterogeneous between countries (Q statistic = 18.03; P = .05), which was explained (P = .023) by the proportion of meat cooked at high temperature (eg, frying, deep frying, roasting, barbecuing, and grilling).

Limitations of this study include possible errors generated by differences in the dietary assessment, collection of dietary information only at baseline, and lack of information on early-life eating habits of participants.

"We have not consistently identified intakes of meat, eggs, or dairy products as risk factors for breast cancer," the study authors write. "Future studies should investigate the possible role of high-temperature cooking in the relation of red meat intake with breast cancer risk."

Funding for this study was provided by a large number of international research foundations, as detailed in the original article. The study authors have disclosed no relevant financial relationships.

Am J Clin Nutr. Published online June 2, 2009.

Clinical Context

Study Highlights

• 319,826 women aged 20 to 70 years were recruited from Denmark, France, Germany, Greece, Italy, Norway, Spain, the Netherlands, and the United Kingdom.
• Exclusion criteria were prevalent cancer at recruitment, missing diagnosis, in situ breast cancer, incompletion of at least 1 diet and lifestyle questionnaire, first and last percentiles of total energy intake to basal metabolic rate ratio, and missing data on confounders.
• Country-specific or center-specific food questionnaires were used to assess food intake in the prior year.
• Exposure variables were total daily intake in grams per day of red meat (beef, veal, pork, and lamb), poultry, processes meat, eggs, milk, cheese, and butter.
• High-temperature cooking was defined as frying, deep frying, roasting, barbecuing, and grilling.
• Countries that cooked up to 45% of red meat by high temperature were Italy, Germany, Norway, Greece, and the United Kingdom.
• Countries that cooked more that 45% of red meat by high temperature were Spain, Sweden, France, Denmark, and the Netherlands.
• Cancer diagnoses were reported by cancer registries, social security records, pathology registries, and follow-up of participants and next-of-kin.
• Each subject was observed until cancer diagnosis, loss to follow-up, death, or end of follow-up.
• Median follow-up was 8.8 years or 2,812,610 person-years.
• 7119 women were diagnosed with invasive breast cancer.
• The UK group had the lowest intake of animal products, excluding milk and butter.
• The most variations in intake occurred for butter (<> 8 g/day for France and Germany) and for processed meat (6.2 g/day for Greece to > 39 g/day for Germany and Sweden).
• Analysis adjusted for energy intake, weight, height, alcohol intake, smoking, education, and menopause status.
• Categoric and continuous multivariate analyses showed that no food group was consistently associated with breast cancer.
• Processed meat was linked with breast cancer in the categoric model only for the last vs first quintile of intake (HR, 1.10; 95% CI, 1.00 - 1.20; P = .065 for trend).
• Semi-skim milk intake was modestly associated with breast cancer in the continuous model (HR, 1.04; 95% CI, 1.00 - 1.09 for each 150 g/day).
• Red meat intake showed significant between-country heterogeneity of HRs.
• Subanalysis showed that the link between red meat intake and breast cancer risk was significant in countries with an increased proportion of high-temperature cooking.
• Analysis stratified by menopausal status showed that high butter intake was linked with breast cancer risk in premenopausal women (HR, 1.28; 95% CI, 1.06 - 1.53).

Clinical Implications

• Intakes of eggs and dairy products are not consistently linked with an increased risk for breast cancer in women.
• Meat intake is not linked with breast cancer risk, although between-country heterogeneity in results might be explained by high-temperature cooking.

Source : http://cme.medscape.com/viewarticle/704523?src=cmenews