It is still unclear whether it is the fat in meat that solicit these harmful effects. Carcinogens could form during cooking, especially by grilling, cooking over a flame, or frying. Then there are nitrosamines, suspected source of all our troubles, were first identified in burned meat and can induce tumors in laboratory animals. It seems, however, that these substances are not responsible for tumors in humans. Hence, the mechanisms that underlie carcinogen-mediated tumor initiation after a rich meat diet remain a mystery.
Meat contains little fiber and has no natural antioxidants.
Eating meat on a daily basis frequently means that you eat fewer vegetables, which are rich in antioxidants. Red meat is also the leading source of methionine in the diet. This amino acid is the direct metabolic precursor of homocysteine, another amino acid, which does not become a building block of protein, but is harmful to arteries. It is also plausible, through not demonstrated, that a high intake of meat can raise levels of homocysteine in the bloodstream. Bearing this in mind, the dietary guidelines established by the American Department of Agriculture in recent years is unconvincing.