A survey published today highlights a link between nutrition and cancer, saying that lowering calorie intake and increasing exercise can reduce a woman's chances of developing breast cancer. The study, published in the British Medical Journal, says that a woman's calorie intake affects the levels of the oestrogen and progesterone hormones produced during the menstrual cycle, high levels of which were linked to an increase in breast cancer. The Polish researchers analysed hormone levels in women from Bolivia, the Democratic Republic of Congo, Nepal, Poland and the US, and discovered that those with a lower calorie intake and more active lifestyles were less likely to develop the disease. The findings offer an explanation as to why breast cancer is more rife in the western world compared with the developing world.