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Red meat and chronic disease

by PAUL ROGERS

Red meat is a dietary staple in developed nations of the west — North America, Europe, Australia and much of South America in the more affluent countries and regions. In fact, eating read meat is almost a badge of affluence. In Asia, red meat is not usually the protein of choice, or availability,  although consumption is rising in countries like Japan and China.

Red meat is defined as beef, pork, lamb, veal and goat in foods like hamburgers, minced beef, pork chops and roast lamb.

Lifestyle diseases, nutrition and red meat

The problem is, individuals with the greatest consumption of red meat — and processed meats like ham, bacon, salami and hot dogs — keep showing up in health studies as having a higher incidence of chronic diseases like cancer, heart disease, diabetes and macular eye degeneration. It seems that consumers of the highest quantities of red meat are more susceptible to these diseases than those who eat the  lowest amounts. And, what makes the data more believable, is that in many studies the same risks do not show up for white meats like chicken, fish and turkey. So what’s going on with red meat?

salad.jpgMost of these investigations are prospective type observational studies where groups of individuals are followed forward in time while their disease outcomes are noted along with their diets. The link between red meat and such diseases cannot really be called “causal” because observational studies like these are not rigorous enough to provide that answer conclusively. Even so, when the same results are found in more than one study, the results become more convincing.

Here are some diseases linked to red meat and processed meat consumption, although not all conclusively.

  • Cancer – bowel (colorectal) and perhaps breast and prostate
  • Type 2 diabetes
  • Cardiovascular disease
  • Macular eye degeneration

An example of how reducing red meat consumption can improve health is demonstrated by a study in which reducing the amount of red meat in the diet improved kidney function substantially in type  2 diabetics as measured by the urinary albumin excretion rate. (de Mello et al.)

 Is it red meat or fewer plant foods?

If these correlations do turn out to be causal, then what is the mechanism of such an effect? There are several candidates.

  • Too much red meat in the diet may result in too few plant foods being ingested and a deficiency of antioxidants, vitamins and minerals that protect against free radicals and other toxic principles. Considering that vegetable protein consumption does not seem to be related to the disease states associated with red meat, this is a reasonable scenario.
  • Heme iron in excess may be toxic. Strange as it may seem, too much iron from red meats may actually cause an excess of free radicals, mutagenic compounds and consequent damage to  all sorts of tissues. This does not seem to be the case with non-heme iron, as in plant sources of iron. There’s more to come on that I’m sure, but it is a favoured causal hypothesis.
  • Burnt meat can contain known carcinogens like polycyclic aromatic hydrocarbons and heterocyclic amines, which might account for colon cancer and other possible cancers.
  • Red  meat as a product of factory farming, feed lots, and various commercial production methods may be contaminated with polychlorinated aromatics like dioxins and PCBs, which are known carcinogens and diabetogens. Free-range and organic production may produce different nutritional profiles.

What you can do to lower the risk

The World Cancer Research Fund recommends limiting consumption of red meat (such as beef, pork and lamb) and avoiding processed meats. They suggest you eat no more than 500 grams (just over a pound), cooked weight per week of red meats, like beef, pork and lamb, and avoid processed meats such as ham, bacon, salami, hot dogs and some sausages. Other sources recommend half this amount or none at all. A medium steak is about 145 grams (about one-third of a pound).

de Mello VD et al. Am J Clin Nutr. 2006 May;83(5):1032-8. Withdrawal of red meat from the usual diet reduces albuminuria and improves serum fatty acid profile in type 2 diabetes patients with macroalbuminuria.

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