There might not be a food that gets picked on more than red meat. “I don’t eat red meat” is almost like a badge of nutritional honor, in some circles.
The World Health Organization spent a couple of years reviewing over 800 studies before releasing, in October of 2015, a fairly brief summary that linked red meat to colorectal cancer. So this wasn’t new evidence, it was just a new summary of past evidence, and it didn’t link red meat to all cancers, only to colorectal cancer.
Anyhow, based on animal evidence and human observational studies (not human randomized trials), the report classified red meat as a carcinogen. To be more precise, processed red meat (like lunch meat and hot dogs) was classified as “causes cancer”, whereas non-processed red meat (like steak) was classified one level lower as “probably causes cancer”.
The report didn’t really show anything new. Red meat is indeed strongly linked to cancer in observational studies, especially prostate cancer … because people who have unhealthy lifestyles tend to eat more red meat (especially the processed kind). But red meat doesn’t cause them to have unhealthy lifestyles.
Still, there are reasons why eating a lot of red meat on a regular basis may increase the risk of prostate and colorectal cancer: the effect of heme iron on intestinal cells, for instance, or compounds created by high-heat cooking, such as heterocyclic amines. Yet red meat isn’t likely to be a major contributor to colorectal cancer in the context of a healthy diet — not only because a healthy diet promotes healthy tissue in general, but also because some vegetables (e.g., broccoli) contain compounds that counteract some of the gut-related effects of red meat.