The Cancer Research UK funded study examined how levels of sex hormones* – known to affect breast cancer risk varied among post menopausal women. Some types of breast cancer are fuelled by the female sex hormone oestrogen. The analysis combined the records of nearly 6,300 post menopausal women from 13 different studies.
Age, type of menopause (natural or caused by surgery to remove ovaries), body mass index (BMI – the measure indicating normal weight, overweight or obesity), smoking, alcohol and reproductive factors were all examined by the researchers based at the University of Oxford.
The findings suggested that the biggest influence on sex hormone levels was BMI scores. The biggest increases were for oestrogens, and this increase in oestrogen may explain why post menopausal, obese women are at higher risk for breast cancer.
Women who drank 20g of alcohol or more per day (around two and a half units) had higher levels of all hormones. One alcohol unit is measured as 10ml or 8g of pure alcohol. A large 250ml glass of wine (12 per cent) is 3 units of alcohol. The higher oestrogen levels may contribute to the increased risk of breast cancer in regular drinkers.
Women who smoked 15 cigarettes a day also had moderately higher levels of all hormones than non-smokers, with the largest difference for testosterone.