The complex process of
carcinogenesis is mainly due to environmental factors and therefore preventable. Diet may account for about 35% of
cancer. This review presents the nutritional evidence for the development of the four most common
cancers in Switzerland. The clearest risk factors for
breast cancer are those associated with hormonal and reproductive factors. In relation to dietary factors, high alcohol intake,
weight gain and adipositas (postmenopausal
breast cancer) probably increase the risk of
breast cancer. The evidence is less clear for the consumption of (animal) fat, meat, fruit and vegetables (inverse association).
Hormones may also play an important role in the development of
prostate cancer. There is no convincing evidence that any dietary factors modify the risk of
prostate cancer. Diets high in vegetables are possibly protective, regular consumption of fat and meat possibly increase the risk. Intervention trials revealed protective effects of supplementation with selen or
alpha-tocopherol. The main cause of
lung cancer is cigarette smoking, and smokers whose diet is protective nevertheless remain at high risk. The evidence that diets high in vegetables and fruit protect against
lung cancer is convincing, but it is not clear what constitutents are responsible for this effect. Intervention trials revealed no protective effect of
beta-carotene, and in high risk groups,
lung cancer risk was even increased. There is convincing evidence that diets high in vegetables decrease the risk of
colorectal cancer. The same is true for regular physical activity. Alcohol and consumption of diets high in (red) meat, probably increase the risk of
colorectal cancer. For
cancer prevention it is recommended to choose a predominantly
plant-based diet, to avoid
obesity, to reduce the intake of
fat, (red) meat, alcohol and
salt, not to
smoke and to be physically active. The main aim of nutritional
therapy of
cancer patients is to improve quality of life, whereas the effect on life expectancy is very limited.