Red meat consumption is associated with an increased risk of certain types of cancer. In some cases this will likely be a result of contamination of the meat with carcinogenic chemicals that directly lead to an increased risk of cancer. However, in other cases this may relates to physiological changes caused by high meat intakes. One example of the latter is the upregulation of the growth hormone insulin-like growth factor (IGF) axis that may occur with consumption of red meat. Some evidence suggests that IGF I and its binding proteins may be related to the risk of developing a number of different cancers. While IGF may cause the proliferation of cells and thus increase the risk of cancer, the binding proteins are able to sequester IGF from interacting with cells, and high levels of the latter may therefore protect from cancer. Red meat may cause an increase in IGF concentrations because of the stimulatory effects certain amino acids such as arginine and lysine which can increase growth hormone production.
Therefore high intakes of animal proteins may increase IGF concentrations in human tissue and this may increase the risk of several forms of cancer. A number of studies have looked at animal protein consumption and tried to relate intakes to blood levels of IGF in the subjects. For example, in one study researchers1 analysed the nutritional diaries of adults who provided nutritional information for a previous study they had participated in during adolescence, and also analysed a stored sample of their blood for IGF and IGF binding proteins. The results of this study showed that higher intakes of animals protein during adolescence in females were associated with higher IGF I serum concentrations and to changes in the amounts of various IGF binding proteins in young adulthood. However, in males high intakes of animal protein in childhood was associated with a reduced blood concentration of IGF I in young adulthood. Animal protein may therefore have differing effects on males and females.
Increasingly, poor quality nutrition during early like, which includes time in the womb, is being shown to produce disease decades later in adult life. The results of studies investigating animal product consumption and IGF production suggest that animal proteins may be another facet to the complex picture of this long-term disease progression. That red meat and animal protein consumption are associated with cancer, does not mean that the red meat and animal protein is the cause of the cancer. Eating less animal protein and more vegetable protein may lower the risk of cancer for example, but vegetables also contain anti-cancer phytochemicals and so the role of the protein itself is not clear. However, it is generally accepted that the poor quality and chemical contaminated meat eaten in the Western diet is a likely contributor to Western lifestyle diseases. In this regard at least, recommendations are to switch from conventionally farmed animal proteins to higher quality organic meats and also to increase vegetable intake.
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