Cooking red meats using high temperature and open-flame cooking methods, such as grilling (broiling) and barbecuing, increase the risk of type 2 diabetes among persons who consume red meat regularly. Why might this be so and how can you consume red meat safely?
In a recently published long-term study more than 59,000 females aged 30 to 55 years were monitored from 1986 to 2012 (26 years).
The study Cooking Methods for Red Meats and Risk of Type 2 Diabetes: A Prospective Study of U.S. Women was published in Diabetes Care, the journal of the American Diabetes Association, in June 2017.
All the women consumed at least two servings of red meats a week. In addition, they were all free of diabetes, cardiovascular disease and cancer at the start of the project.
Information on how often the subjects used various methods of cooking red meat … including broiling (grilling from the top down), barbequing, roasting, pan-frying, stewing and boiling … was also gathered at the start.
Just over 10.5% of the women developed type 2 diabetes (T2D) over the two-and-a-half decades of the study, more than the average for the population as a whole. Both total red meat and processed red meat were associated with an increased risk of T2D.
But the increase in risk varied depending on the cooking method used.
Compared to persons who ate red meat once a month or less often, those who ate two or more servings a week had:
- a 29% increased risk of developing T2D if the meat was broiled (under flame),
- a 23% increased risk if the meat was barbequed, and
- a 11% increased risk of T2D if the meat was roasted.
In addition, when meat was stewed or boiled there was no higher risk of developing T2D. And, strangely, when meat was pan-fried (a high heat method of cooking), the risk was reduced.
But what causes the increased risks when red meat is broiled, barbequed or roasted?
You can blame three chemicals:
- Heterocyclic amines (HCAs)
- Polycyclic aromatic hydrocarbons (PAHs)
- Advanced glycation end products (AGEs)
These chemicals have been linked to inflammation, diabetes, obesity and cancer.
Heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs)
HCAs and PAHs are chemicals that are formed when muscle meat … beef, pork, fish or poultry … is cooked at high temperatures, over or under open flames.
HCAs are produced when amino acids (the building blocks of proteins), sugars and the creatine found in muscle react at high temperatures. HCAs are only found in foods that have been cooked at high temperatures.
PAHs are made when fat and juices from meat grilled directly over an open fire (ie, barbeque) drip onto the fire causing flames. The flames carry the newly created PAHs back up and they adhere to the meat.
PAHs can also be formed when meat is being smoked. They can also be found in cigarette smoke and car exhaust fumes.
The formation of HCAs and PAHs during cooking varies depending on the type of meat, the cooking method used, and how well cooked (rare, medium or well done) the meat becomes.
Whatever the type of meat, cooking it at a high temperature (over 300 degrees F), or cooking it for a long time, tends to form more HCAs. Well done steak or chicken, whether barbequed or grilled, contains high concentrations of HCAs. Exposing meat to smoke or charring also forms PAHs.
HCAs and PAHs have been found, under laboratory conditions, to be mutagenic … ie, they cause changes in DNA.
Advanced glycation end products (AGEs)
Glycation is the bonding of a sugar molecule, such as glucose or fructose, to a protein or lipid molecule without the bonding being controlled by an enzyme.
Glycation impairs the functioning of biomolecules. A biomolecule is a molecule that is involved in the maintenance and metabolic processes of living organisms.
Advanced glycation end products (AGEs) are proteins or lipids that have become glycated by being exposed to sugars. AGEs affect nearly every type of cell and molecule in the body.
They can be a factor in aging and in the development or worsening of many degenerative diseases, such as diabetes, atherosclerosis, chronic kidney disease, and Alzheimer’s disease. They are also believed to play a causative role in the vascular complications of T2D.
Most foodstuffs contain small quantities of AGEs.
Dry heat promotes the formation of AGEs across most food categories … in some food stuffs this can be up to a 100 times more than the food in its uncooked state.
Foods derived from animals that are high in fat and protein are generally AGE-rich and prone to the formation of new AGE during cooking. By contrast, carbohydrate-rich foods such as vegetables, fruits, whole grains, and milk contain relatively few AGEs, even after cooking.
How can you reduce the risk from red meat?
The World Cancer Research Fund and the American Institute for Cancer Research issued a joint report in 2007 that recommended limiting the consumption of red, processed and smoked meats.
Nevertheless there are no official guidelines as to how meat eaters can reduce the formation of HCAs, PAHs and AGEs.
Here are some common sense measures you can use to reduce your exposure to these chemicals:
- Use a variety of cooking methods
- Use moist heat … braising (stewing slowly in a closed container), steaming or poaching … as often as possible
- Avoid direct exposing meat to an open flame or a hot metal surface
- Avoid prolonged cooking times (especially at high temperatures)
- Cook as slowly as possible (at lower temperatures)
- Use acidic ingredients … lemon juice or vinegar … in marinades
- Use a microwave oven to cook meat before finishing off with high heat
- Turn meat that is on a high heat source over continuously
- Don’t eat charred portions of meat
- Don’t make gravy from meat drippings