Friday, May 07, 2010

High-Heat-Treated Meat Linked To Cancer, Diabetes, and Heart Disease

I usually don't double dip with my diabetes work, but since I was on the topic of meat-eating from yesterday... To recap:

The President's Cancer Panel's upcoming report advises against eating meat that was cooked at high temperatures, e.g. grilled, seared, broiled, charred, fried, or well-done.

Compounds formed during high-heat cooking raise the risk for gastrointestinal cancers.* Since these chemicals are always formed in meat - beef, poultry, fish, and other animal tissue - that has been cooked, just eating cooked meat more often, regardless of its form of preparation, raises cancer risk.

*From the National Cancer Institute's Fact Sheet on Heterocyclic Amines:
  • "[People] who ate their beef medium-well or well-done had more than three times the risk of stomach cancer than those who ate their beef rare or medium-rare."
  • "People who ate beef four or more times a week had more than twice the risk of stomach cancer than those consuming beef less frequently."
  • "An increased risk of developing colorectal, pancreatic, and breast cancer is associated with high intakes of well-done, fried, or barbequed meats."
How does this relate to diabetes? High-heat-treated foods are increasingly being linked to insulin resistance. A study in this month's American Journal of Clinical Nutrition...

A Diet Based On High-Heat-Treated Foods Promotes Risk Factors For Diabetes Mellitus And Cardiovascular Diseases

... found that those who consumed more high-heat-treated foods (compared to mild steam cooking) had:
  • Decreased insulin sensitivity
  • Decreased blood levels of omega-3
  • Decreased blood levels of vitamin C
  • Decreased blood levels of vitamin E
  • Increased cholesterol levels
  • Increased triglyceride levels
Another support for eating the Paleo Vegetarian diet.


Perovskia said...

I don't understand; 'cause humans have been cooking meat over fires for thousands of years, have we not?

Bix said...

Humans have been eating cooked meat for thousands of years, yes.

What I don't know is ... how much meat the majority of humans ate, and what impact that had on their health.

caulfieldkid said...

This is actually one of the questions I was going to ask on your paleo blog. It was my guess that high heat applications to meat caused carcinogens. Would never have guessed it was linked to diabetes though.


Matthew said...

I have wondered for a while if the negetive effects of meat consumption that appear in population research are caused by the cooking methods rather than the meat itself. Grilling, searing, broiling and frying are almost universal ways of cooking meat in the western diet now. These techniques are hard to do without metal, a quite recent invention.

Our ancestors have been cooking for a very long time. I would speculate that cooking with wood camp fires may produce less of the harmful compounds. Intense heat is formed where the meat is in contact with the metal of the grill or frying pan. Ancient cooking may have involved more use of indirect heat or baking, wrapped in leaves, under the embers of the fire. Spit roasting next to a camp fire is unlikly to reach the temperatures as under an electric grill.

I expect some of the more tender bits of meat like liver would have been eaten raw when fresh.

MermaidLilli said...

I have a hard time believing many studies that are not very well controlled. If they had separated groups....1. Meat eaters who do not overcook their meat and who do not eat processed carbs. 2. Meat eaters who do not overcook their meat and who do eat processed carbs. 3. & 4. The above but overcooking their meats. And these groups have to be followed by decades. I am sure there needs to be even more groups. ie. North Americans who eat nothing but meat and fat with a little bit of other foraged foods, another few groups who also consume fast foods, fried foods and excess sugars... see what I mean?

Bix said...

It's true. You can always design a better study. You can always conduct a better study. No study has proven that smoking causes lung cancer yet.

ElDoubleVee said...

Our ancestors died young before most cancers had a chance to kill them. Cooking methods didn't matter nor did their diets matter since they would probably die of injury, infectious disease or animal attack way before the accumulative effects of bad diets had a chance kill them. You don't care what your cholesterol count is when you are trying to avoid having your skull crushed by a saber-toothed tiger. We live longer and the accumulative effects of bad diets show up in cancers and heart disease.

Anonymous said...

This is old, but people who eat "well done" meat, tend to be lower-economic class (I suspect). Meat that tastes good medium to rare, tends to be higher, more expensive cuts of meat. Once you factor in economic class, all of this makes sense.

Also, people who eat meat multiple times per week -- as opposed to seafood and a good cancer-preventing whole grain diet -- probably do not exercise, etc. This study makes some very blanket claims.....

Bix said...

People keep making this point about controlling and confounding. This was not an epidemiological study. Those types of studies can be confounded by the things described, such as 'people who eat meat may not exercise, how do you know it's not the lack of exercise.'

This study was a randomized, crossover, diet-controlled, intervention trial. 'Crossover' means both groups ate both types of food, the mild-steamed as well as the high-heat. They switch halfway through, with a washout period between. These types of studies virtually eliminate confounding.