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Does red meat cause colorectal cancer?

Published by Arnold Page in Food and fitness · 9/2/2016 15:55:00
Tags: red_meat_and_bowel_cancerred_meat_and_colorectal_cancerred_meat_cancer
Last October we were once again threatened with the dire consequences of eating red meat. ‘Red meat cancer risk to be revealed by World Health Organization’ the BBC announced on its web site, hurriedly retracting this a few hours later and substituting, ‘Processed meats do cause cancer’. The same stories about red and processed meat surface every few years.
The particular report that the BBC and all the newspapers referred to was a press release (no. 240) issued by the World Health Organization’s International Agency for Research on Cancer headed ‘IARC Monographs evaluate consumption of red meat and processed meat’. ‘Red meat’ means the muscular parts of beef, veal, pork, lamb, mutton, horse, and goat. (It’s important to understand that when such reports talk about ‘red meat’ they do not mean only beef.) ‘Processed meat’ means meat that has been transformed through salting, curing, fermentation, smoking, or by the addition of chemical preservatives such as pink sodium nitrite. Examples of processed meats are bacon, sausages (unless freshly prepared in-store), frankfurters, ham, salami, luncheon meat and corned beef.
After reviewing the accumulated scientific evidence, the 22 experts comprising the IARC committee classified
(i)  red meat as probably carcinogenic (cancer-producing) to humans, and
(ii) processed meat as carcinogenic to humans. (This put it in the same class as tobacco, smoking and asbestos.)

“Aha! Another lovely scare-mongering headline,” the so-called science correspondents of our national newspapers cried gleefully. “Processed meat is as bad as smoking,” the Daily Express announced. “Processed meat ranks alongside smoking as major cause of cancer,” the Daily Telegraph reported.

Such headlines blatantly ignored the IARC’s own statement that assigning processed meat to the same class as smoking and asbestos does not mean that it is equally dangerous. While eating a lot of processed meat appears to increase the risk of colorectal cancer by 20%, smoking increases the chance of contracting lung cancer by 600%. Once again the media distorted facts simply to attract attention and increase sales.
But back to red meat. After examining as many relevant existing research papers as possible, the IARC report concluded that people who eat around 130 gm of unprocessed red meat a day are 17% more likely to contract colorectal cancer than those who eat about 30 gm a day. Hence it is ‘probably carcinogenic’. I regard this conclusion as misleading, unscientific, irresponsible and immoral. It was probably motivated by a desire to discourage the eating of meat for reasons unrelated to health, in particular environmental considerations, over which there is considerable argument. So what is my justification for this indictment?
  1. Statistical links between two facts do not prove that one causes the other. If 99% of deaths occur in bed, then it could be argued that our chance of dying is increased by 9900% if we get into bed, but that doesn’t mean that beds kill us or that we should sleep on the floor.
  2. The authors of the report themselves stated that their conclusion was ‘based on limited evidence of positive associations’ and that ‘other explanations could not be ruled out’.
  3. The data on which this conclusion was based came from a wide range of ‘countries, ethnicities and diets’, among whom those who ate most meat would generally also have been those who also ate most processed food of all kinds including sugar- and salt-loaded products. It is quite likely that such groups also drank more alcohol and took less exercise than other population groups. Some of these other factors could well have been responsible for the increased prevalence of cancer among those groups. For example a study carried out in 2015 at a university in Shanghai found that regular beer drinkers had a 20% greater risk of bowel cancer compared with non-drinkers or occasional drinkers. A correlation between meat and alcohol consumption would mean that the increased prevalence of bowel cancer among larger meat eaters was nothing to do with eating meat but entirely due to the fact that they drank more alcohol.  
  4. A review of all relevant studies has shown that Asian meat eaters are actually healthier than vegetarian Asians. Asians with a vegetarian orientation seem to get more heart disease and more cancer than others. Years ago Dr Weston Price found that the Inuit (Eskimo) people ate nothing but meat and fish for 9 months of the year and had no cancer or heart disease. Since meat did not cause cancer in these populations, something other than meat may be responsible for the association of colorectal cancer with diets relatively high in meat in other populations.
  5. No distinction was made in the report between the various kinds of meat that people ate – beef, lamb, pork, chicken, etc. It might be that beef is unhealthy and chicken is perfectly healthy, or vice versa. Without such a breakdown in the data the conclusion that all meat is probably carcenogenic could be very misleading.
  6. No attention was given to the quality of the meat people ate. Many animals nowadays are raised on artificial diets high in grain and seed-oils. Even grass may be treated with pesticides, biocides and nitrates. Organically farmed meat might not be linked even statistically with an increased risk of cancer. The study should not have lumped naturally and unnaturally grown meat together.
  7. No attention was given to other dietary constituents. One contributing report found no link between colectoral cancer and red meat intake except among large meat eaters who also ate very few vegetables.

Those are the reasons I regard the conclusion as misleading and unscientific, and that is why I think that it was motivated by factors other than pure science or an honest desire to improve the world’s health. One might as well conclude that since 99% of people who paint their nails are women it must be painting one's nails that turns someone into a woman.
I also regard the conclusion as irresponsible because red meat is the best source of protein for a given number of calories, it is a major source or iron, zinc and vitamin B12, and it helps to maintain a healthy omega3:6 balance. Many people who reduced their meat intake in response to reports like this would eat more carbohydrates instead, thereby increasing their weight and worsening the imbalance in their omega fatty acids. Discouraging meat eating could actually worsen a nation's health.
Furthermore I regard the conclusion as immoral because by putting people off meat eating it unnecessarily harms the livelihood of primary meat producers.

Finally I regard it as unduly alarmist. The NHS reports that 1 in 20 people will contract bowel cancer during their lifetime. If you are an average meat eater this is your chance of contracting bowel cancer. A large meat eater with an 8.5% increased risk would have a 1 in 18.4 chance of contracting bowel cancer, and a small meat eater with an 8.5% decreased risk would still have a 1 in 21.8 chance. Those are fairly small changes! Yet even these changes depend on there being a 100% causal link between eating meat and contracting cancer, whereas as we have seen the association between the two may be due to other factors altogether.
Having said all this, the fact remains that among many populations there is a small but statistical association between eating red meat and bowel cancer, and it must be due to something. There are four obvious possibilities, and all four may contribute to the association.
1.  High consumers of red meat tend to belong to population groups who eat a lot of factory-produced food, which nowadays is usually high in temperate seed oils (bad for the omega 3:6 balance and free radical production), carbohydrates (leading to obesity and excess sugar production by the liver), sugar and salt. The same population groups probably drink relatively high quantities of alcohol and eat relatively few fresh vegetables and fruit. All of these habits are associated with cancerous growths. The way to eliminate such causes is to adopt a healthy diet such as the 25:45:30 Natural Health Diet I recommend in my book ‘Twenty-First Century Nutrition and Family Health’. About twenty years ago I developed polyps, often a precursor to bowel cancer, which were removed under anaesthetic. Since I adopted a healthier diet there has been no recurrence of them so far as I know, and my 5-yearly checkups were stopped.
2.  A lot of red meat, whether factory- or home-cooked, is cooked nowadays in temperate seed oils such as sunflower oil, rapeseed oil or maize (‘corn’) oil. These largely polyunsaturated fats oxidise when heated producing harmful free radicals that cause internal inflammation which is responsible for all kinds of disease. Before seed oils replaced animal fats such as dripping and lard for cooking, bowel cancer was significantly less common than it is today. For the sake of your health, as well as your taste buds, cook with beef dripping, pork lard, butter or goose fat, or else tropical oils like virgin olive oil, coconut oil or palm oil from sustainable sources, for these contain higher proportions of saturated fat and can therefore withstand higher temperatures than temperate oils can, without decomposing.
3.  Some meats, particularly when barbecued, fried or grilled, reach very high temperatures and can even char. It is known that carcinogenic substances are produced at high temperatures, particularly in processed meat treated with the pink-coloured preservative sodium nitrite. So avoid over-cooking meat, bacon, sausages and similar products, and never eat any parts that are blackened or charred.
4.  Intensively-farmed cattle graze on grass treated with artificial fertilizers, pesticides and biocides, and are fattened on maize and other cereals for which their digestive systems are not designed. In the USA in particular the animals are treated with antibiotics and growth hormones which might have further health implications for human beings. It is certainly possible that the kind of meat we are eating is partly a cause of cancerous growths. If you can afford it, buy organically produced meat and poultry to avoid any possibility of cancers caused by artificial feedstuffs and chemicals.
  1. The statistical link between eating a lot of red meat and contracting cancer of the colon or rectum is significant, but so small that even if it were a 100% cause-and-effect link, reducing one's meat intake would not alter very much one's chance of contracting bowel cancer, and the resulting change in diet might produce other health problems instead.
  2. For organically produced meat at least the link is almost certainly due to factors other than the meat itself.
  3. Even for non-organically produced meat the link is probably mainly due to other dietary or lifestyle factors or cooking methods, which can and should be corrected.
  4. Meat is a good source of some essential dietary components, and if it is cooked in a healthy manner and eaten in reasonable quantities as part of a healthy diet it is unlikely to be harmful, particularly if it is produced organically and naturally.

What are 'reasonable quantities'? Many of the reports studied assigned people to one of five groups depending on how much meat they ate. One typical report defined the middle group of average meat eaters as men who ate 35 gm of meat per 1000 kcals and women who ate 26 gm per 1000 kcals. If we assume that the average total daily food consumption in this study was 3000 kcals for men and 2500 kcals for women, then an average or (presumably) reasonable meat consumption would be 105 gm per day for men and 67 gm per day for women.

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