When it comes to our health, we often focus on what to eat and what not to eat. But just as important is how we prepare the foods we eat. Certain cooking methods can unleash chemical by-products that have been linked to heart disease, diabetes, Alzheimer’s and other chronic diseases.
Sugar is a clingy molecule that attaches to amino acids and fats and changes their structures—a process known as glycation. This triggers a complex chemical reaction that culminates in the production of advanced glycation end products (AGEs). They’re sometimes called “glycotoxins” because they trigger inflammation and can lead to cell injury and cell death.
Almost all foods contain AGEs. They’re naturally produced by the body as well. But their number vastly increases during food preparation, particularly when you cook with dry, high heat.
Small amounts of AGEs aren’t a problem—most are excreted through the kidneys. But the foods that many people prefer—particularly those that are high in sugar and fat and are cooked certain ways—are teeming with AGEs. The body can’t cope with the excess, so the AGEs pile up over time. This leads to…
More heart disease. AGE-modified proteins and fats can accumulate in blood vessel walls and stimulate clots—the cause of most heart attacks. AGEs also form chemical “cross-links” that stiffen blood vessels and cause high blood pressure.
Uncontrolled diabetes. The high blood glucose (blood sugar) that is the hallmark of diabetes provides fuel for AGE formation. AGEs damage pancreatic cells (resulting in less insulin)…make insulin less effective…and increase diabetes complications, including nerve and blood vessel damage.
More cognitive decline. AGEs damage the protective barrier that insulates the brain from the rest of the body. This allows AGEs to damage brain-specific proteins and produce amyloid plaques—the deposits that occur with Alzheimer’s disease. In laboratory studies, animals given a high-AGE diet were much more likely to experience harmful brain changes than those given healthier foods.
More kidney disease. AGEs can injure the blood vessels and other parts of the kidneys, causing them to become scarred and shriveled and greatly reducing their ability to excrete AGEs. As kidney function declines, AGE levels rise in the blood, flooding all tissues of the body and setting the stage for even greater damage to the kidneys and all other organs as well. Studies have shown that patients with chronic kidney disease who are treated with a low-AGE diet have a decrease in circulating AGEs, as well as in levels of markers of inflammation and oxidative stress.
The inflammation from excessive AGEs has been linked to many other conditions, including arthritis, obesity, vision problems and even skin wrinkles.
CUT AGES IN HALF
You can reduce your AGE levels by 50% in as little as one month. Best steps…
Add moisture, and reduce the heat. Any form of high-heat cooking—mainly grilling, broiling, frying and roasting—greatly increases AGEs. Examples: The 500 kilounits (kU) in one serving of raw meat might increase to 5,000 kU after broiling. Moist-heat cooking methods—such as poaching, stewing and braising—are ideal. Consider one serving of chicken. It will contain 600 kU to 1,000 kU when it is stewed or braised, but up to 6,000 kU when it’s roasted or grilled.
It is fine to have roasted or grilled food now and then. What’s Thanksgiving without roast turkey! But try to limit how often you have these foods.
Marinate. This is a good solution for meat lovers. The acidic ingredients in most marinades—such as lemon juice, wine, tomato juice and vinegar—greatly inhibit AGE formation even when meat is grilled. Depending on the meat’s thickness, marinating it for one to two hours will reduce AGEs by up to 50%.
Choose lower-AGE foods. In general, this means eating less meat, cheese and fat and more produce (see below). Beef, poultry and pork have the highest levels of AGEs.
Important: Fatty meats tend to have more AGEs than leaner cuts, but even lean meats will readily produce AGEs when they’re prepared with dry heat.
Eat minimally processed cheeses. They aren’t cooked, so why are some cheeses so high in AGEs? It is because they’re heated during processing and because aging and the removal of liquids during cheese-making increase AGE formation.
My advice: Eat lower-fat cheeses with shorter aging times that undergo the least processing. Cheddar cheese made with 2% milk, for example, has about half the AGEs of cheeses made with whole milk. Avoid Parmesan cheese (2,500 kU) and American cheese (2,600 kU).
Get more flavonoids. These are naturally occurring compounds that appear to activate enzymes that deactivate AGEs, inhibit AGE-related oxidation and trap the molecules that can increase AGE formation. Good sources: Apples, chili peppers, berries, broccoli, kale and green or black tea. Spices and herbs that have similar effects include turmeric, cinnamon, parsley, rosemary and sage.
Go easy on the sweets. Even though sugar and other sweeteners don’t contain a lot of AGEs, levels increase when they’re heated—when you’re baking, for example, or during the factory production of breakfast cereals. High-sugar foods often contain fats and proteins, which increase the potential for harmful chemical reactions.
Warning: The fructose in many soft drinks and processed foods causes a 10-fold greater rate of glycation than simple glucose. Dark-colored soft drinks (such as colas) are particularly bad because the color comes from caramelized (dry-heated) sugars. Diet colas contain nearly the same amount of AGEs as their sweetened counterparts.
Very Low (100 kU/serv or less)—Bread • Eggs (poached, scrambled, boiled) • Fruits (fresh) • Grains (boiled, steamed) • Milk • Soy milk • Vegetables (fresh, steamed) • Yogurt
Low (101–500 kU/serv)—Avocado • Fruits (dried, roasted, grilled) • Legumes (cooked, canned) • Olive oil • Olives • Pasta • Soy veggie burgers • Vegetables (roasted, grilled)
Medium (501–1,000 kU/serv)—Cheese (reduced-fat) • Chicken (poached, steamed, stewed, braised) • Chocolate (dark) • Fish (poached, steamed) • Sunflower and pumpkin seeds (raw) • Tofu (raw) • Tuna or salmon (canned)
High (1,001–3,000 kU/serv)—Beef or pork (stewed, braised) • Butter • Cheese (full-fat and processed varieties) • Fish (grilled, broiled, baked) • French fries • Nuts (raw) • Sweets (donuts, pies, cakes, pastries, etc.)
Very High (3,001–5,000 kU/serv)—Chicken (skinless, broiled, grilled, roasted) • Fish (breaded and fried) • Pork chops (pan-fried) • Single cheeseburger (fast food) • Grilled cheese sandwich • Tofu (broiled, sautéed) • Turkey (roasted)
Highest (5,001 kU/serv or more)—Bacon (fried) • Beef (roasted, grilled, broiled, well-done) • Chicken with skin (broiled, grilled, roasted) • Chicken (fried, fast-food nuggets) • Double cheeseburger (fast food) • Fish sandwich (fast food) • Hot dog • Sausage • Pizza