Meat is regularly accused to be a direct cause of cancer. Recently, the largest prospective population study on over half a million people has been published with the conclusion that red and processed meat intakes were associated with modest increases in total, cancer, and CVD (cardiovascular disease) mortality (1). When looking closer into that study it can be noticed that "modest" refers to an increased risk of somewhere between +11% and +38%. Considering that total cancer death rate is usually around 0.2% the enhanced risk seems rather weak to negligible than modest in practical terms and only of academical interest. Furthermore, when looking at meat one should concentrate only on large bowel cancer, since meat intake hardly would lower the incidences of breast, lung, prostate, or pancreatic cancer as a report of the Committee on Medical Aspects of Food (2005) concluded.
Of a dozen previous prospective studies which reported meat intake and subsequent large bowel cancer, only two - both from the US - found a significant association. Even in those the association was weak and only seen in people with the highest quintile of meat intake. As well as this accumulation of mostly negative prospective studies, a multinational combined report of 5 follow up studies of vegetarians and socially matched omnivore controls (total 76 000 subjects) found the relative risk of colorectal cancer in the vegetarians to be 0.99 (indistinguishable from 1.00). Furthermore, the bunch of existing observation studies is poorly suitable for the causal prove of correlations because of its retrospective nature and concomitant memory biases, as well as the long development time of cancer. But such studies may have contributed a great deal to public awareness of meat and cancer, as well as to the so-called publication bias; Obviously, when undertaking a study on the association of meat intake and cancer a researcher will postulate the hypothesis that there is a causal correlation. If the results do not prove the hypothesis, he is likely to have problems to find a willing publisher for such a "negative" study result or even unwilling himself to publish it. Such practices may lead to the publication of only positive outcomes to a certain hypothesis and falsify the picture.
However, the outcome and the relevance of the actual study on Meat Intake and Mortality is further compromised because subjects who consumed more red meat tended also to be a current smoker, have a higher body mass, have a higher intake of fat and energy, have lower education and physical activity and lower fruit, vegetables, fibres, and vitamin intakes. Certainly, it is possible to correct study results for various confounders like smoking and body mass. Still, also in this very study a positive association for processed meat intake and cancer mortality could be found for former/current smokers but not among never smokers. But how does an increased risk for death from injuries and sudden death, which was demonstrated for males in the study, causally fit with eating red meat? May be there was some dangerous slaughtering and grilling activities involved when treating red meat in contrast to buying processed meat at the supermarket? Because there was no association for processed meat intake and death from injuries and sudden death in both sexes.
Finally, there is very good evidence about the health advantages of omega-3 fatty acids, mainly occurring in fish, regarding blood lipid profile, CVD and also cancer. Now, this may explain the stated "small decrease in total and cancer mortality" with high white meat intake, seen that fish was counted as white meat in the dietary profile assessment of the study. Following that root it should be mentioned that contemporary cattle show disadvantageous lipid profiles due to grain concentrate feeding strategies. Cattle feeding on grass or game deliver a very advantageous omega-3 to omega-6 fatty acids ratio. In that respect the reverse conclusion is also possible that nowadays the unhealthy fatty acid profile of "red and processed meat might fail to play a protective role against the development of cancer" rather than to promote cancer. But whether meat is a direct cause of enhanced cancer risk or not remains uncertain. More plausible seems the role of the proven carcinogenic substances deriving from heavily "black" grilled meat (PAHC: polycyclic aromatic hydro-carbons) - and from the overly heating carbohydrate-containing foods and coffee for that matter (acrylamide)! Noteworthy, red and processed meat is probably more likely to be grilled than fish and also chicken. At least the latter two are not grilled as dark as a beef steak or a cured bacon from an experienced barbecue master. This may constitute an important difference and a bias in the individual exposition to carcinogenic PAHC for which one cannot correct in the statistics of a study!
In a British study looking at the blood lipid profiles in meat-eaters, vegetarians, and vegans it was seen that eating meat caused a much higher plasma content of CLA (conjugated linoleic acid) compared to vegetarians (-33%) and vegans (-62%). Besides, vegetarians and vegans showed also 30-60% lower contents of the health promoting omega-3 and mono-unsaturated fatty acids. What one might claim a healthier fatty acid profile in meat-eaters stands in contrast to the widely accepted assumption that vegetarianism constitutes a healthier regimen. Interestingly, the considered disadvantageous arachidonic acid was similar in all three groups, whereas the ratio of linoleic acid to alpha-linolenic acid again was more advantageous, i.e. lower, in similarly health-conscious meat-eaters than both vegetarians and vegans. Recent studies have also shown higher plasma homocysteine (a CVD risk factor) concentrations than in non-vegetarians. Vegetarian diets are usually rich in carbohydrates and fibres. However, diets rich in protein, good fat, and lower in carbs are linked to even better heart health than the so-called DASH diet (Dietary Approaches to Stop Hypertension).
How these data add to a thinking-over of the actual nutritional fat - especially of animal origin - and meat intake recommendations has still to be discussed, but it certainly cannot be neglected, and must not be equated with the predominating meat and fatty acid profile of nowadays' nutrition. Meat is the major source of available iron, vitamin B12, zinc, and protein. There is of course no need to char or heavily brown meat, poultry, or fish when frying or grilling, and is generally accepted and recommended not to. But nutrition is not black and white! Rather than to worry and skip meat from the dishes it is recommended to pay attention to a sufficient, i.e. high, intake of vegetables and salad which will provide you with enough antioxidative capacity to handle carcinogenic substances from all food sources.

Literatur:

(1) Meat intake and mortality. Sinha R. et al, Arch Intern Med, 169(6), 2009