There is evidence to suggest that some dietary components can reduce the risk of breast cancer. In this pilot study two such components, isoflavones (compounds found in soy products) and selenium, will be given to women classed as at moderate to high risk of the disease. The aim is to determine some novel biomarkers of risk and to see the effect of supplementation on them.

The high incidence of breast cancer, its relatively long development phase and the financial burden to the NHS in relation to treatment makes it a prime target for dietary preventative strategies. Epidemiological and experimental investigations suggest several key dietary components that may reduce breast cancer, in particular isoflavones and selenium. Few dietary intervention studies have been conducted to investigate putative protective effects, but with our growing understanding of cancer biology and the application of new -omics technologies it is now possible to use early biomarkers of risk to assess the potential efficacy of intervention studies.

In this pilot project, we will employ a combination of disciplines to examine the effect of dietary intervention in a group of women defined by NICE guidelines as being at increased risk (moderate-high) of developing breast cancer, using metabolomics to assess the tractability of biomarkers in response to the dietary intervention. Such trials are urgently needed to examine the protective effects of diet in women classified at increased risk and who are still in the 'zone of reversibility'. The results of this study will be used to justify and optimise larger scale intervention trials and ultimately to develop appropriate dietary recommendations for the prevention of breast cancer.

A dietary intervention study based on a randomised double-blind parallel design will be conducted in 30 pre-menopausal women (age 35-50) at moderate to high risk of developing breast cancer. The metabolomic profiles of urine and serum samples (collected at baseline and after dietary intervention) will be assessed. Participants will be randomised into two groups; the placebo group (consuming 6g of non-supplemented chocolate per day) and the supplemented group (consuming 6g of chocolate containing both soy and selenium per day). The intervention will last for the duration of one menstrual cycle.

Inclusion Criteria:

• Pre menopausal women (age 35-50)at moderate to high risk of breast cancer based on family history (NICE guidelines)
• Attending Breast Clinic at NNUH
• Willing to consume 6g of chocolate per day for 25-35 days
• Regular menstrual cycle of 25-35 days in length

Exclusion Criteria:

• Current or previous diagnosis of breast cancer or cancer of any other site
• Diagnosis of hypertension (requiring active treatment)/diabetes/ coronary heart disease/ gastrointestinal disease/ any other systemic disease requiring treatment
• Regularly taking any prescribed medication within the last six months (including oral contraceptives)
• Fitted with a hormone releasing device
• Pregnant or lactating in the previous 12 months
• Using laxatives or antacids more than once a week
• Routinely taking soy or selenium supplements in the last twelve months
• Regularly taking any dietary or herbal supplements in the last six months
• Participation in any intervention study (soy or selenium) in the previous twelve months
• Parallel participation in another research study involving either dietary or medical intervention or sampling of biological fluids/materials
• Blood donation within sixteen weeks of study start/finish
• BMI <18.5 or >35
• Allergy to any chocolate/dairy/soy-based food products