You already know that “you are what you eat,” as the saying goes. But did you know that it’s not only what you eat that makes you healthy (or not), but how hot you cook your food. Subjecting certain foods to prolonged high heat—not only for frying, but also for grilling, roasting, broiling or baking—creates toxic inflammatory particles. These, in turn, cause the oxidation and inflammation in the body that are associated with such diseases as diabetes, heart disease, kidney disease, Alzheimer’s and others.
Called advanced glycation end products (AGEs), these toxic particles adhere to the arteries, kidneys, brain and joints, where they heighten inflammation. Our typical Western diet, heavy on meat and processed foods and light on plant-based foods, is believed by many scientists to contain at least three times more AGEs than is considered safe.
To find out how to avoid AGES, our editors turned to Helen Vlassara, MD, professor of experimental diabetes and aging and medicine at Mount Sinai School of Medicine in New York City, who conducted the research.
GOOD NEWS FROM THIS STUDY
It’s always exciting when research reveals a way toavoid a common health problem—and this new study does just that. According to Dr. Vlassara, you can achieve dramatic and quick benefit—within just days—by reducing your intake of AGE-containing foods. Doing this decreases the body’s level of inflammation and helps restore its defenses against disease.
The study divided 350-plus participants into three groups—healthy adults between the ages of 18 and 45… an older healthy group, all past age 60… and nine patients with chronic kidney disease (the kidneys are believed to be especially sensitive to AGEs). Participants were randomly assigned to eat either a regular Western diet in which foods were grilled, fried or baked—in other words, loaded with AGEs—or what the researchers called “the AGE-less diet,” which included the same foods, only poached, boiled or steamed so that they contained only about half as many AGEs. The two diets were similar in calories and nutrients. After four months, all participants on the AGE-less diet showed a 60% decline in blood levels of AGEs as well as in several other inflammation markers.
According to Dr. Vlassara, this indicates that your actual chronological age may not be as significant a factor in aging and health as the AGEs in your food. A finding that’s even more impressive: The patients with kidney disease had a similarly substantial reduction after just one month on the AGE-less diet.
THE HEAT IS ON…
We asked Dr. Vlassara to explain how the AGEs get into foods. She explained that they develop as a chemical reaction when heat is combined with protein and different sugars—and noted that meat-rich diets are especially bad, since meats contain high levels of easily oxidizable fat and protein.
There is a third point that is crucial to understand—which is that removing all visible fat when you cook meats doesn’t solve the problem. All cells in meats contain not only fat and proteins, but also sugars—some more reactive than others. Therefore, exposure to high heat will still cause AGEs to form in meat at much higher levels than in starch even if you cut away the visible fat. In fact, Dr. Vlassara explained that when you see meat brown while cooking, what you’re witnessing is the rapid reaction among proteins, fats and those reactive sugars to the heat. And because full-fat milk and cheese also are animal products, they, too, develop high levels of AGEs when they are cooked.
Even worse, manufacturers often add AGE-containing flavor enhancers or coloring (such as caramel) to processed and packaged foods. You may be surprised to learn that a major offender in this category is dark-colored soda. Generally speaking, fast foods and processed/packaged foods also tend to be high in AGEs, which gives us yet another reason to avoid them.
The good news is, it’s not all that difficult to reduce the amount of AGEs in your diet, Dr. Vlassara said. It just requires making some modest changes in the way you prepare food. Her suggestions…
- Marinate in an acid-based mixture (such as vinegar or lemon juice) before cooking, which helps reduce the amount of AGEs produced by heat. Note: Avoid marinades containing sugar, such as most barbecue and teriyaki sauces.
- Aim to serve meats rare to medium rare if possible—for instance, cooking pork to just beyond pink. This is admittedly a balancing act—you want to cook as briefly as possible to minimize development of AGEs, but undercooking carries its own set of dangers.
- To achieve a brown finish to meats, Dr. Vlassara suggested cooking on your stovetop with a cover to conserve moisture, and then placing the meat under the broiler for just a few minutes at the end.
- Use as little fat as possible—as Dr. Vlassara pointed out, even healthy olive oil oxidizes at high heat.
- Water inhibits the formation of AGEs, so poaching, stewing, steaming or even boiling proteins is best (including fish and eggs).
DAIRY AND OTHER FOODS
- Avoid bringing dairy products to high temperatures—for instance, when using milk in sauces or when melting cheese under a broiler. Dr. Vlassara said the less time these foods cook, the better. She added that lower temperatures are preferable, as is increased distance from the heat source.
- Brief microwaving produces a lower level of AGEs than broiling, grilling or stovetop cooking, so this is a great way to cook liquids.
- Plant-based proteins also create dangerous levels of AGEs when subject to very high heat for long periods—so be aware that there are dangers to even seemingly healthy foods like broiled tofu or roasted nuts.
WHAT ABOUT RESTAURANT FOOD?
Fortunately, the increasingly popular Mediterranean diet uses lots of foods with low AGEs (including fruits, vegetables, beans and whole grains), so it once again ranks among the healthiest ways that you can eat. This not only provides a good framework for eating at home, it also suggests a wide variety of delicious, healthful, low-AGE dishes that you can order in restaurants. But Dr. Vlassara noted that cooking even these foods at high heat with low hydration is problematic, so there’s no way around it. Bottom line: Cooking at high temperatures is not so hot for your health.