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Ultimate Nutrition Column
Is The Barbecue Putting You In Danger?
Susan M. Kleiner, PhD, RD, FACN, CNS, FISSN Let's get this out of the way right up front. Is the barbecue putting your health in danger? It might be. Does that mean you should trade in your grill for a stew pot? Not yet.For years nutritionists have been watching the research about the chemical changes that happen in foods when protein and fat are cooked at very high temperatures. We have read about the production of potentially carcinogenic molecules when the fat from meats drip onto the hot coals of the grill. More recent reports point to the production of a new class of toxins, advanced glycation endproducts (AGEs), which develop during cooking and accelerate aging and serious chronic conditions such as diabetes, heart disease, and hypertension. While it sounds like a barbecued burger could do you in as quickly as a pack of cigarettes, the comparison isn't even close. When it comes to grilling, broiling and even oven frying, moderation and variety are the keys to good food and good health. Increasing Oxidative Stress Oxidative stress is caused by an imbalance in the cellular systems that are charged with detoxifying molecules that can cause damaging chemical reactions or in the systems that easily repair the resulting damage. This imbalance can produce reactive oxygen species including free radicals and peroxides, and even cell death. The causes of increased oxidative stress in aging are not fully understood, but it is clear that a high production of reactive oxygen species plays a significant role in chronic diseases such as cardiovascular disease, renal disease, and diabetes. AGEs are triggers of reactive oxygen species. They also stimulate the inflammatory response and the systemic immune response that has been linked to instigation of arterial plaques in the development of cardiovascular disease, and they are often elevated in diabetic subjects. AGEs may be associated with Alzheimer's Disease. While AGEs are produced as a normal part of metabolism, they have also been identified in food, especially in foods with significant protein and fat content that have been processed using high heat, such as grilling, roasting and broiling. A recent study has linked the amount of AGEs in the diet with the level of AGEs and markers of oxidative stress in the bloodstream.1 The study also demonstrated that blood levels of AGEs are elevated in older individuals. However, independent of age, as the level of dietary AGEs increased so did blood levels of AGEs. These increases were correlated with parallel increases in markers of oxidative stress and inflammation. According to the researchers, "these findings point to the potential role of dietary and circulating AGEs in age-related diseases, especially of older adults." Decreasing AGEs in Your Diet The process of heating foods increases the amount of AGEs in the food, but not all heating affects AGE production similarly. At Mount Sinai Hospital in New York City researchers prepared foods and then measured the amount of AGEs produced. Foods were prepared for standard cooking times with commonly used cooking methods: boiled in water (100oC), broiled (grilled) (225oC) deep fried (180oC), oven fried (230oC), and roasted (177oC).2 AGEs are also naturally found in raw foods. When foods were classified into food groups and measured before cooking, the fat group contained the highest mean AGE food values. Butter and processed cream cheese, margarine and mayonnaise showed the highest amounts, followed by oils and nuts. The meat and protein group followed with the next highest AGE values. From highest to lowest were cheeses, beef and poultry, tofu, fish and whole eggs. Once these were cooked, exposure to the highest temperatures created the greatest AGE content: oven frying>deep frying and broiling (grilling) >roasting>boiling. While it may seem surprising that oven frying results in a higher, and more unhealthy AGE content compared to deep frying, it is due to the very high temperatures. Deep fried foods are cooked for a shorter time at a lower temperature. According to the researchers, although the data were not presented, microwaving was similar to boiling in the production of AGEs. Carbohydrate-based foods contain the lowest amounts of AGEs. Within the category the foods with the highest AGE content were processed items, due to both high temperature cooking and high-pressure extrusion to create the shapes and textures of processed cereals, crackers, pretzels, and other processed foods. Grains, legumes, and starchy vegetables and breads were much lower. The lowest AGE values were measured in the milk group, then vegetables and fruits. If you are already following the recommendations for a healthy diet you are automatically selecting foods that are generally lower in AGEs. A diet low in processed foods and abundant in fruits and vegetables, with several daily servings of dairy, including eggs, fish, poultry and vegetable proteins as your major protein sources is going to be low on the AGE scale. How you prepare your foods on a regular basis is also important. According to Karen Friedman-Kester, MS, RD, LDN, a faculty member in the Culinary Arts Program at Harrisburg Area Community College, poaching fish and braising meats, along with stewing and microwaving are the cooking techniques that produce the fewest AGEs. Stir frying would likely follow next on the list. "Braising is a form of poaching for meat," says Friedman-Kester. "Sear it lightly and then add liquid and simmer to break down the tough connective tissue of the meat." Meats that work best for braising include sliced turkey, veal, pork and low fat meats that can't be tenderized with dry heat. Don't Give Away Your Grill It's probably clear by now that the key to a diet low in AGEs is to include the great variety of foods naturally low in AGEs, and to include smaller amounts of foods that are high in AGEs, using high heat cooking methods like grilling and broiling on an occasional basis. The effect of grilling, broiling and oven frying becomes even more pronounced with foods already high in AGEs, particularly red meat. And frankly there doesn't seem to be a big advantage to oven frying at all. The health gain from the lower fat content may be overridden by the very high levels of AGEs produced in the high heat of the oven. As you age, if you already have a diagnosis of heart disease, diabetes or renal disease, or you know that you are at high risk of developing those diseases, controlling AGEs in your diet may have an even greater impact on your health. It's what you do day in and day out that matters. So if you live in the sunbelt (or not) and use your grill every day, it's probably prudent to get out of the sun and use your indoor stovetop and oven more regularly. When you do grill or broil, stick with fish and vegetables most of the time. But when it comes to opening day at the ballpark, Memorial Day, Fourth of July, and Labor Day holidays, a burger or steak on the grill can still be part of the celebration. Low AGE Recipe Easiest Salmon ½ pound wild salmon filet 1 ½ teaspoons olive oil juice from ½ lemon ½ teaspoon dill pinch of kosher salt
References Uribarri J, Cai W, Peppa M, Goodman S, Ferrucci L, Striker G, Vlassara H. Circulating glycotoxins and dietary advanced glycation endproducts: Two links to inflammatory response, oxidative stress, and aging. J Geronotology 2007;62A:427-433 Goldberg T, Cai W, Peppa M, Cardane V, Baliga BS, Uribarri J, Vlassara H. Advanced glycoxidation end products in commonly consumed foods. J Am Dietet Assoc 2004;104:1287-1291
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