Previous epidemiological studies have investigated the relationship between individual nutrients such as vitamin D and vitamin B12 and mammographic density, a strong marker of breast cancer risk , with varied results. There has been limited research on overall dietary patterns and most studies have focused on adult dietary patterns . We examine prospective data to determine whether dietary patterns from childhood to adult life affect mammographic density.
The Medical Research Council National Survey of Health and Development is a national representative sample of 2,815 men and 2,547 women followed since their birth in March 1946 . A wealth of medical and social data has been collected in over 25 follow-ups by home visits, medical examinations and postal questionnaires. Dietary intakes at age 4 years were determined by 24-hour recalls and in adulthood (ages 36, 43 years) by 5-day food records. Copies of the mammograms (two views for each breast) taken when the women were closest to age 50 years were obtained from the relevant NHS centres. A total of 1,319 women were followed up since birth in 1946 for whom a mammogram at age 50 years was retrieved, and the percentage mammographic density was measured using the computer-assisted threshold method for all 1,161 women. Breast cancer incidence for the whole cohort is being ascertained through the National Health Service Central Register.
Reduced rank regression analysis, a relatively new approach to dietary pattern analysis, is being used to identify dietary patterns associated with mammographic density . This approach identifies patterns in food intake that are predictive of an intermediate outcome of the disease process, such as mammographic density, and subsequently examines the relationship between the identified dietary patterns and breast cancer risk.
Preliminary analyses so far suggest that variations in dietary patterns in adulthood might explain more than 10% of the variation in percentage mammographic density at age 50 years (age 36 years: 13%; age 43 years: 14%), with variations in patterns in childhood explaining slightly less. Further work is being carried out on the characteristics of these dietary patterns and their effects on percentage mammographic density and its two components (that is, absolute areas of dense and nondense tissues) and on breast cancer risk, after adjusting for socioeconomic status, anthropometric variables and reproductive factors.
The present study will provide for the first time information on the relationship between dietary patterns across the life course and mammographic density, and will help to clarify the pathways through which diet may affect breast cancer risk.
Breast Cancer Campaign UK–World Cancer Research Fund International and the Medical Research Council fund this project. IdSS and VM are members of the Cancer Research UK Epidemiology and Genetics Group; VM is funded by a Cancer Research UK training fellowship.