Diet and Breast Cancer: insights from the EPIC study

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The European Prospective Investigation into Cancer and Nutrition (EPIC) [i] study is one of the world’s largest ongoing cohort studies[ii], following over half a million people from ten European countries for almost fifteen years. Among its main objectives is to understand the influence that diet, nutrition, lifestyle and environmental factors have on the incidence of cancer and other chronic illnesses.

The study’s recent findings on breast cancer are particularly revealing, and affect younger and older women in different ways.

by Professor Luis Costa

Weight gain may increase risk

The EPIC study confirms a strong connection between excess body weight and increased incidence of breast cancer in menopausal women. Moreover, post-surgery weight gain has been found to increase the risk of cancer recurrence.

The majority of breast cancers contain hormonal receptors (oestrogens and/or progesterone receptors) and are considered hormone-dependent in some way. However, the increased incidence of breast cancer due to high BMI (body mass index) is observed both in cancers showing hormonal receptors and in those with none at all.

The challenge for scientists and doctors is to understand what exactly occurs in the body after a significant increase in BMI that causes the changes in breast tissue leading to carcinogenesis, or the growth of pre-existing cancer cells.

a photo of Professor Luis Costa

The importance of folates

Until now, our main recommendations regarding breast cancer and diet have been to maintain weight and limit alcohol. However, women often want to know what more they can do, and if they can make changes to their diet to increase their protection.

In this respect, the EPIC study is a major first step towards more focused guidelines on diet and breast cancer. The study followed 367,993 women from 35 to 70 years old, in 10 European countries, for an average period of 11.5 years. From this group, 11,575 women with breast cancer were identified. As the women were given country-specific dietary questionnaires, it was possible to estimate dietary folate intake. Folate, also known as vitamin B9, plays an important role in a number of bodily functions and is required for DNA synthesis and repair. The body cannot create its own folate, and folic acid has to be supplied through the diet to meet our daily requirements through folate-rich plants like dark green leafy vegetables. Alcohol has been proven to decrease folate levels.

When comparing younger, premenopausal women, the study found a 14% reduction in breast cancer risk (with no hormonal receptors) for those women who had a significant alcohol intake (more than 12 alcoholic drinks per week) yet who also got adequate levels of folate. The study’s authors conclude that a higher dietary folate intake may be associated with a lower risk of breast cancer with no hormonal receptors in premenopausal women.

EPIC research is ongoing, and we expect more insight in the future that will assist in the prevention of breast cancer. For now, keep your weight under control and make sure your diet is rich in folates, particularly if you drink alcohol. Good sources of folate include spinach, asparagus, Brussels sprouts, nuts, beans and peas.

Professor Luis Costa is Director of Oncology at Lisbon’s Hospital de Santa Maria and a member of the Best Doctors European Medical Advisory Board.

 

[i] Dietary folate intake and breast cancer risk: European prospective investigation into cancer and nutrition. Batlle J, et al. J Natl Cancer Inst. 2014 Dec 12;107(1):367. doi: 10.1093/jnci/dju367.

[ii] A cohort study is follows a selected group of people over a set time period, usually monitoring their response to a treatment or risk factor.

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