Red Meat Bashing: Facts vs. Dogma
This article has been written by our guest author, Dr Mark JS Miller, who is President of Marketing and Chief Science Officer at Healthy Directions. He has a PhD from the University of Adelaide and a MBA from La Trobe University. Dr Miller has previously worked as a professor at Albany Medical College and at LSU Medical Center New Orleans.
It seems that it is now popular, even amongst the scientific community, to find ways to bash red meat as a health detractor. In these campaigns the supportive science is vague at best, not well designed (largely association studies) and alternative explanations for the observations not given due notice. Let me help sort through the issues so you can make better decisions for your health.
Production of TMA/TMAO & Atherosclerosis
The Hazen group in Cleveland kicked it off a few years ago, with discussions that red meat drove cardiovascular disease (1). At least they proposed a mechanism of action, which was the production of TMA (trimethylamine) in the gut and its subsequent conversion to TMAO (trimethylamine oxide) in the liver. With TMAO being pro-atherosclerotic it was touted as being the link between a meat diet to cardiovascular disease. The publicity around the study and its author made lots of press and helped cement the notion of red meat being bad for you.
However, if you dig into the data there were flaws in the conclusion, which I discussed at length in an editorial in the Journal of the American College of Nutrition (2). In essence, TMA was generated via gut flora, as aptly shown when antibiotic treatment eliminated TMA production. So it is a bacterial product not inherent to a specific diet. Numerous nutritional substrates can be used by gut bacteria to make TMA. Furthermore, there was the large overlap of TMA levels in vegetarians & meat eaters. Indeed, 75% of the TMA levels in meat eaters were identical to 90% of all vegetarians. If red meat were the culprit there would not be ANY overlap. Explanation, TMA levels reflect how the diet interacts with gut flora. If you have the wrong gut flora you make excess TMA (2), it is not a red meat thing.
A core issues is not the science per se but is a headline thing. A publication just recently showed there was no impact of red meat consumption on metrics for cardiovascular health (3). This publication did not get the same reactions in the press as the scare tactics. Over time the sensational headlines get embedded in recommendations from healthcare experts.
Cancer: Cooking Methods and Processed Meats
Here the attack includes BBQs or very high heat cooking, to create a class of chemicals, aryl hydrocarbons, which when studied in isolation can cause cancer. But there is a big difference between injecting mice with these chemicals and slapping a steak or burger on the grille. Nevertheless the IARC keeps commenting on it and pushing the WHO with this agenda. But guess what in their last report they noted there was no effect of cooking method on the incidence of colon cancer (4). Yes these chemicals can be formed but the dose is not enough to make any difference. However, they still kept the recommendations. I guess they were really wedded to the concept.
In the same report (4) processed meats were placed in the same class of carcinogens as plutonium, tobacco and asbestos. That is an excellent way to establish a total loss of credibility with the public. They just do not believe it, and for good reason. The proposed mechanism of action here is the formation of nitrosamines, chemicals that are carcinogenic, from dietary nitrite/nitrate.
This is a case of terrible chemistry. It just does not happen. Let me explain. The reaction requires a positively charged NO+ group replacing the H+ on an amine to form the nitrosamine. The problem is that nitrite (NO2 -) is negatively charged, not positively charged. Remember the term “chemical equation”, it means both side are equal, so here we have lost 2 electrons without explanation. In simple terms the reaction just does not occur. Dreadful science.
Furthermore, if dietary nitrate/nitrite were the key culprit then ANY food with high levels would show the same pattern. Here it just becomes silly, because leafy green vegetables and beets have very high levels of nitrate, much more than processed meats, and are associated with a reduced incidence of colon cancer not a higher level. The entire argument that red and processed meats cause colon cancer falls apart without a single viable mechanism of action. What they may have been observing was what was absent from the diet (fiber and fruit) rather than what was present in the diet (red meat). That changes the recommendations away form do not eat red meat to please eat more fiber, vegetables and fruit. Far less controversial but yet meaningful for the public.
Diverticulitis & Red Meat Consumption
Diverticuli are pouches in the large intestine and in some people that can become swollen, inflamed (diverticulitis) and very painful. These pouches can swell to the point of bursting with the colonic contents released into the abdomen. Not a good thing. A recent report linked an increase incidence of diverticulitis to red meat consumption (5) but this report did try to sort through other potential contributors.
The subjects with the highest incidence of diverticulitis were obese, did not exercise, smoked, had a low dietary fiber intake, displayed inflammation and took high levels of NSAIDs. These drugs which limit the cytoprotective actions of prostaglandins in the gut, which is why they cause ulcers. Despite these factors it was red meat that was singled out as the primary culprit.
To help sort through this let’s look at what is happening in the disease of diverticulitis. Here the lining of the colon wall is ballooning out and essentially thinning to the point of busting liked a popped balloon. There are enzymes, called MMPs, that are activated during inflammation that breakdown the matrix, the collagen, that holds the tissue together. Normally they are dormant, their genes turned off, but during inflammation they breakdown this matrix and in this case leads to swelling & perforation. Fiber can manage this process; the byproducts of bacterial fermentation can help keep these enzymes dormant.
The authors did acknowledge that a disturbance in the profile of gut bacteria may be a factor in the inflammation and diverticulitis but did not test for it. Low fiber diets, disturbed gut flora and NSAIDs are far more likely to be the explanation. If meat is involved it may be due to antibiotics present in the meat as growth promoters, which in turn creates a disturbed gut flora or dysbiosis and colon inflammation. However, that is not the take home message, rather we are told that red meat causes this colon disease.
Telomere Length & Red Meat
While controversial the length of telomeres – the caps on the ends of chromosomes – are used to reflect longevity both cellular and whole body. When telomeres become too short the chromosome and its DNA unravels and the cell dies. In other words in the world of telomeres longer is better. In a recent study (6) 9 different food groups (cereal, fruits, vegetables, diary, red meat, poultry, fish, sweets and salty snacks) and 8 different beverages (juices, coffee, tea, mineral water, alcoholic- and sweetened carbonated beverages) were used as challenges/strata and then determine the impact on telomere length.
Of all of the interventions ONLY red meat was associated with an increase in telomere length. Does that mean that eating red meat will make you live longer? I think that too is an overstatement but at least this observation not compatible with the current dogma and the headlines associated with that belief system that red meat is bad.
All in all everyone should be encouraged to have a balanced diet. Red and processed meats are not the sinister beasts that are trying to run you into poor health. Be skeptical, look at the details and sort the propaganda from the data. I suggest that the headlines are superseding the message and recommendations for public health, which is sad day for science. We need to do better.
Links to Citations
- Heart disease and redmeat correlation may not be about saturated fat
- Islow-fat milk really better for you?
- UK obesity forum criticiseslow-fat diets