A vegetable to meat consumption ratio as a relevant factor determining cancer preventive diet. The Mediterranean versus other European countries

Abstract

The observed growth of cancer incidence in certain regions has been usually linked to frequent consumption of 'unhealthy' food. Such food often contains genotoxic substances as heterocyclic aromatic amines (HAAs) and/or polycyclic aromatic hydrocarbones (PAHs), occurring during food preparation, which induce DNA damage in cells. These substances are mainly formed during frying or grilling of meat and they can be removed from the body in a two-stage metabolic process of detoxification (phase 1 and phase 2). If they are not excreted, they form DNA adducts. The effectiveness of detoxification depends on the activity of enzymes encoded by polymorphic genes. A diet containing plenty of fruits and vegetables, due to the presence of biologically active polyphenols, can modulate activity of detoxifying enzymes. Such a diet can decrease the extent of DNA adducts, breaks and oxidative damage, supporting the body's enzymatic system in sufficient removal of DNA damage. The antioxidant vitamins' content in such a diet also enhances the DNA protection by increasing the scavenging of radical oxidative species that occurs during metabolic reactions. The lack of balance between the amount of 'unhealthy' and 'healthy' food leads to the accumulation of unrepaired damage, initiating DNA instability and inducing cancer development. Such damage is often used as a biomarker of cancer risk in epidemiological studies. Moreover, in in vitro studies, the amount of the DNA damage is used as indicator of the protective ability of vitamins, plant extracts and/or individual flavonoids. The incidences of certain dietaryrelated cancers in European Mediterranean countries is lower than in Central and Northern European countries; there is simultaneously variation in the habitual diet in these regions. This suggests that some features of routine nutrition in the Mediterranean countries may be responsible for this preventing effect. However, inconsistency in the epidemiological data, associating the meat and fruit and vegetable intake with cancer risk, suggests that another strategy for evaluation dietary influence on cancer risk should be undertaken. This article argues that it is not the consumption of a single food product or an individual component of diet, but rather a proper ratio of vegetable to meat consumption that is responsible for cancer prevention. This hypothesis is tested comparing the association between certain dietaryrelated cancer incidences (colon & rectum, breast and prostate cancer), registered in 2002, with the ratio between consumption of these two groups of food products in the Mediterranean region and in Central and Northern European region over the last three decades. The results clearly showed that both the ratio between vegetables and meat consumption as well as the ratio between the amount of energy from vegetables and from animal products can be used successfully to evaluate the dietary pattern related to cancer risk.