Regularly eating meat and cooked foods changed our anatomy. Our teeth became smaller and less pointy, our colons shrank and our small intestines grew, all of which improved our ability to chew and digest soft, cooked foods. Calorie-dense meats likely enabled the tripling of our brain size as well. These and other adaptations helped our ancestors survive in a time very different from our own. The pertinent questions for today are whether the diets of our evolutionary past have any bearing on our current situation and how our modern approaches to preparing and consuming meat change our health.
Reservations about Preservation
In trying to answer these questions, it is important to note right away that nutrition research is notoriously difficult to conduct. After all, scientists cannot ethically force some people to dine exclusively on red meat while others munch on lettuce to demonstrate the long-term health effects once and for all. But researchers have done the next best thing: surveying large groups of people about their diets.
Two studies from different teams of Harvard researchers exemplify the growing recognition that not all types of meat are equally unhealthy. This past spring Frank Hu and his colleagues concluded that eating red meat was indeed linked to a greater risk of cardiovascular disease, cancer and death from any cause. Specifically, each additional daily serving of unprocessed red meat (a serving is about the size of a deck of cards) increased the chances that someone would die by 13 percent; processed meat bumped up the death risk to 20 percent. These risks were calculated over a 22-year period for men and 28 years for women.
Translating those numbers into everyday terms requires some sophisticated math. Statistician David Spiegelhalter of the University of Cambridge used Hu's results to calculate that an adult who eats an extra serving of red meat each day would lose one year of life expectancy. Consider what that means for a healthy 40-year-old male, who can be expected to live another 36.2 years, according to FindtheData.org's analysis of the relevant Social Security data. Instead of making it just past his 76th birthday, he instead lives to 75.2 years. Nothing to shrug off—but certainly not the most deadly habit. Men and women who smoke, for example, lose an average of 13.2 and 14.5 years of life, respectively according to the Centers for Disease Control and Prevention.
Hu's study was not without limitations. It relied on self-reported surveys, which can skew the results in several ways. Equally problematic, it turns out that the participants who ate the most red meat were also more likely to smoke, drink alcohol in excess and exercise less often, making meat consumption seem unhealthier than it may truly be.
An alternative to Hu's conclusions emerged from another team at Harvard, led by Mozaffarian, who compiled and reviewed the results of 20 studies on eating meat. These 20 studies included data from more than 1.2 million people, whereas Hu's study looked at data from just over 120,000. The meta-analysis found no greater risk of death or disease tied to red meat in general; instead it singled out the dangers of processed red meat, such as bacon, salami and hot dogs. Mozaffarian and his colleagues associated each daily 50-gram serving of processed red meat with a 42 percent higher risk of heart disease and a 19 percent higher risk of diabetes.
As in Hu's study, people who eat a lot of hot dogs and cold cuts might be less healthy overall. But such strong associations from a large review are nonetheless intriguing. Why would processed red meat be so much worse than unprocessed red meat? Both have fairly similar levels of saturated and unsaturated fats. In every 50-gram serving, however, processed meats contain more calories and less cholesterol, protein and iron than red meat.
See what we're tweeting about
24 Comments
Add CommentColon = large intestine. "our colons shrank and our large intestines grew" should probably be "our colons shrank and our small intestines grew".
Reply | Report Abuse | Link to this"increased the chances that someone would die by 13 percent"
Reply | Report Abuse | Link to thisThe chances anyone will die is of course 100 per cent.
it's all about balance. You cant have any pudding if you don't eat your meat.
Reply | Report Abuse | Link to thisThe problem is excess. We are very adaptable omnivores, and a balanced omnivore diet is the best thing for our organism. Start abusing any aspect of it for too long and you run into trouble. Start abusing non-natural stuff that our metabolism is not prepared for, and you run into trouble much faster.
Reply | Report Abuse | Link to thisJust be smart. No need to juggle details so much...
"he stores his meat in a large white freezer chest in his shared Manhattan apartment"
Reply | Report Abuse | Link to thisThat is precisely the reason believed for the increased death rate , the ability to have meat on hand all the time , refrigeration.
The problem being the increased uncontrolled iron absorption from meat.
Evidenced in a few different studies in which they showed the highest iron levels in those who consumed meat.
"Participants who frequently consumed reindeer meat had higher levels of s-ferritin (P < 0·0001) than did individuals with other dietary patterns. This pattern was highly represented by subjects with three generations of Sami language (Sami I). Further, mean transferrin saturation in the reindeer group was higher compared with the other dietary clusters for men (P < 0·04) and women (P < 0·02)."
PLUS the fact meat enhances other iron , so the iron added to the bread in your roast beef sandwich is absorbed too , at a higher rate , as in , it wouldn't even BE absorbed if you didn't eat meat.
"Iron: Minerals and Electrolytes: Merck Manual Home Edition
Eating small amounts of meat, which contains the easily absorbed form of iron (heme iron), enhances the absorption of the poorly absorbed form of iron "
"Meat Protein Fractions Enhance Nonheme Iron Absorption in Humans"
"Beef and chicken muscle increased iron absorption 180%"
Normally we downregulate the amount of iron we absorb but the meat iron doesn't seem to listen and is absorbed.
"Adapted to absorb less nonheme iron (3.2% at week 12 compared with 5.0% at week 0, P:<0.001) but not less heme iron from a beef-based meal"
This buildup of iron explains the increased heart disease found in women when they reach menopause.
Reply | Report Abuse | Link to thisThey no longer are protected FROM the iron because they have lost their menses which are thought to lower the iron levels in women , compared to men , who manifest heart disease earlier , due to the iron buildup.
This is again evidenced in diabetes.
"Consuming red meat and other foods high in "heme" iron, such as chicken liver, clams and oysters, appears to increase the risk of heart disease in diabetics, researchers report in the journal Diabetes Care"
"It might be advisable that "patients with type 2 diabetes may limit consumption of heme iron and red meat,"
Which seems to reiterate the fact in Unmmannaq , Greenland , they found the highest iron levels and later found also to have the highest diabetes rate , and the difference , the higher iron was attributed to heme iron / meat iron .
"The observed differences in estimated body iron
stores in Greenlanders from the three residential areas can be explained by differences in the dietary intake of haem iron"
"Diabetes in Unmmannaq was higher than that in the towns of Nuuk and Qasigiannguit"
When one considers the increased iron stores , one has to wonder whether it IS the iron from meat which causes disease in man , as evidenced here , tuberculosis ?
Reply | Report Abuse | Link to this"A full blown proliferation of the mycobacteria
population can be activated as soon as the levels of free iron are elevated within the host tissues"
Reply | Report Abuse | Link to thisI am glad the article distinguishes between preserved and non-preserved red meats, but dismayed that no finer distinction was made in the latter category.
As your Paleo diet adherent John Durant is obviously well aware, the meat consumed by our ancestors did NOT come from factory-farmed livestock raised in horribly crowded, unclean and inhumanely stressful environments, and forced to live on a diet it did not evolve to eat -- i.e., predominantly or exclusively grains (genetically-modified at that, and perhaps supplemented with antibiotics and hormones). Such environments and such diets are anything but healthful for the animals, so how can meat from such unhealthy, unnaturally-raised animals possibly be healthful for us?
As your Harvard epidemiologist says, “Not all meats are the same. We have choices.” Besides largely eschewing processed, preserved meats, omnivores who are serious about a healthful lifestyle, such as Mr. Durant, choose meat from animals living closer to the way they evolved to live. Ruminants -- cattle and bison, sheep, goats, deer, etc. -- evolved to eat mainly GRASS (and whatever insects they might take in along with it), NOT pesticide-dosed "Round-up Ready" corn or soybeans. The meat -- and the fat -- from wild animals and from organically "pasture-raised" livestock is believed to be far more wholesome for us. I hope someday these not-insignificant distinctions will be recognized, and studied, in the ongoing debate about the proper role of red -- and other -- meats in our diets.
These researchers think , iron damages a gene AND iron causes cancer.
Reply | Report Abuse | Link to this"Scientists discover how iron levels and a faulty gene cause bowel cancer"
"Iron could be raising the risk of bowel cancer by increasing the number of cells in the bowel with APC faults"
That is what he said in the article. "our colons shrank and our small intestines grew"
Reply | Report Abuse | Link to this"Hu's study is not without it's limitations" is a polite way of saying it is embarrassingly bad! The quintiles show no progression; the quintiles are clearly very different in many, many ways. Read Gary Taubes review for full night into this deeply flawed study.
Reply | Report Abuse | Link to thisI would highly recommend the documentary : Meet Your Meat.org. for all carnivores. Bon appetit!
Reply | Report Abuse | Link to thisAs to the Palaeo Diet: It does not really deserve the term palaeo, 'old', as does not hold water in evolutionary terms, as those Neandertalian times with their ice age meat from the 'permafrost freezer' were only the blink of time, compared with millions of African vegan nutrition years that went into our primate genome before!
Read 'The China Study' for the health hazards of animal protein, and weigh your own risks.
Physicians for Responsible Medicine are a good information source when it comes to latest research- clearly not sponsored by the meat industry.
No, read the editor's note.
Reply | Report Abuse | Link to thisVilifying salt is without merit. Studies have been so unable to demonstrate a problem that even the anti-salt faction has been forced to explain lack of confirmation by saying "only some people are 'salt sensitive'", and "the reason salt reduction didn't show benefit is that even the reduced amount is too much."
Reply | Report Abuse | Link to thisTrouble is, even studies that down-selected to "salt sensitives" have been unable to confirm an effect.
The other alternative is that salt isn't harmful.
Another odd thing, is the approach to studying the effect of sodium reduction. Invariably, studies rely on self-reported ingestion rather than direct measurement of sodium levels. Self-reporting is very inaccurate. Direct measuring techniques exist and can accurately demonstrate salt ingestion. But the larger question, also never answered, is what is the change in serum sodium concentration from ingesting lots of salt? Sodium concentrations are tightly controlled of necessity by the kidneys; does anyone believe that ingesting an additional gram or two of salt results in significantly higher serum sodium concentrations? If there is no increase, then what is the harm? It isn't magic; if serum concentrations aren't elevated then the rest of the body, apart from the kidneys, doesn't even "know" that there is excess salt.
The statement "Some processed meats also contain nitrosamines, which form nitrites when meat is cooked at high temperatures or exposed to the acidity of the human stomach." is incorrect. Nitrites are used to preserve many processed meats, such as hot dogs. In the gut they are converted to nitrosamines which are known carcinogens. This is a plausible explanation for at least part of the reduced lifespan associated with regularly eating processed meats.
Reply | Report Abuse | Link to thisThe page now shows that this error got corrected.
Reply | Report Abuse | Link to thisYou know what it really boils down to? Don't worry too much about eating meat. Just live your life. You're going to die sooner or later, and it just might be tomorrow. Take reasonable care of yourself, but enjoy what you enjoy while you can. You won't get a second crack at it.
Reply | Report Abuse | Link to thisIf you buy beef or lamb from New Zealand, you get meat from animals that live out in fields and eat grass. What you might call solar powered farming. That is why meat and milk and cheese from New Zealand is so cheap and without subsidy.
Reply | Report Abuse | Link to thisEat you meat, but not alone! Successful diets of healthy traditional societies incorporate many nutrients that cooperate with one another to produce excellent health; muscle meat together with organ meats and gelatinous materials such as bones, gristle and connective tissue provides a balance between the methionine found in muscle meat, the B vitamins in organs, and the glycine in connective tissues in a synergy we are only just starting to understand.
Reply | Report Abuse | Link to thisMethionine contributes to cell growth and repair, cellular communication, antioxidant defense and detoxification. However! In order to perform these functions in a controlled methylation cycle methionine must be balanced with B vitamins and choline from organ meats! Without the protective nutrients found in organ meats, methionine fails to contribute properly to the methylation process and generates a toxic byproduct called homocysteine. When adequate b vitamins and choline are provided but the diet lacks adequate glycine found in bones, skin and other connective tissues, then the methylation cycle kicks into over drive leading to a excessive methylation stimulating a dangerous breakdown in cellular communication and glycine depletion which contributes to the negative consequence of cellular aging. Adequate glycine works in synergy with the protective nutrients found in ample amounts in organ meats to prevent excessive methylation and to ensure the adequate conversion of methionine to glutathione – the master antioxidant in the body, ensuring that methionine will be used for proper cellular communication and as part of the cellular defense against oxidants and environmental toxins.
Enter the modern diets, which, provides ample muscle meat, but not organs and connective tissue resulting in gross imbalances and a breakdown in cellular communication. This is clearly the reason we see so many observational studies linking chronic disease such as CVD to meat consumption.
Eat you meat, along with the liver and gristle!! Successful diets of healthy traditional societies incorporate many nutrients that cooperate with one another to produce excellent health; muscle meat together with organ meats and gelatinous materials such as bones, gristle and connective tissue provides a balance between the methionine found in muscle meat, the B vitamins in organs, and the glycine in connective tissues in a synergy we are only just starting to understand. Methionine contributes to cell growth and repair, cellular communication, antioxidant defense and detoxification,
Reply | Report Abuse | Link to thisHowever! In order to perform these functions (methylation cycle) methionine must be balanced with B vitamins and choline from organ meats! Without the protective nutrients found in organ meats, methionine fails to contribute properly to the methylation process and instead generates a toxic byproduct called homocysteine. When adequate b vitamins and choline are provided but the diet lacks adequate glycine found in bones, skin and other connective tissues, then the methylation cycle kicks into over drive leading to a dangerous breakdown in cellular communication and glycine depletion which contribute to the negative consequence of cellular aging. Adequate glycine works in synergy with the protective nutrients found in ample amounts in organ meats to prevent excessive methylation and to ensure the adequate conversion of methionine to glutathione – the master antioxidant in the body, ensuring that methionine will be used for proper cellular communication and as part of the cellular defense against oxidants and environmental toxins.
Enter the modern diets, which, provides ample muscle meat, but not organs and connective tissue resulting in gross imbalances and a breakdown in cellular communication. This is clearly the reason we see so many observational studies linking chronic disease such as CVD to meat consumption.
"In order to perform these functions (methylation cycle) methionine must be balanced with B vitamins and choline from organ meats!"
Reply | Report Abuse | Link to thisThe B vitamins are found in the grain we eat WHEN we do not overrefine the grain. The methionine is also produced from our grains WHEN they are not overrefined and the choline removed. Choline is what produces methionine.
"Supplementation with lecithin, choline, or betaine resulted in a significant increase in plasma methionine"
Salt AND detary iron COMBINED spells trouble , for the rat , at least.
Reply | Report Abuse | Link to this"Dietary Iron Restriction Prevents Hypertensive Cardiovascular Remodeling in Dahl Salt-Sensitive Rats "
Respondent no. 8, melkat: The description of "factory farms" is inaccurate. Pigs reared in confinement buildings are not stressed due to overcrowding. If so, they would not grow well. The buildings are clean, not unsanitary. Pigs reared in unsanitary conditions become sick and do not grow. Pigs in confinement are warmer, no snow, and are protected from predators such as coyotes. True, videos have captured the unacceptable conditions described by this respondent. BUT, this is not the norm. The logical view is pork producers are seeking profits; thus, those who practice such poor management can not derive a sustained profit. It is unfortunate that modern pork producers continue to be evaluated based upon videos of deplorable living conditions for pigs.
Reply | Report Abuse | Link to thisIf you're lucky enough to live in Australia Kangaroo is very tasty with almost no fat and they just haven't found a way to get skippy to take those antibiotics yet.
Reply | Report Abuse | Link to this