We have been discussing AGEs (advanced glycation end-products) in food in the past few posts. In our body they contribute to premature aging of the tissues in our bodies and lead to the early onset of diseases associated with aging. The traditional thoughts about AGEs are changing as we learn more about them. A recent study (1) of over 500 foods gives new insight into what contributes to AGEs in food. Today we will look at the cooking and preparation methods that affect AGEs in foods.
Factors Affecting AGE In Food
What the food is composed of is the main determinant of the AGE level in food. There are three main factors that change the AGE level from what the AGE level in the raw food is. They are the temperature the food is cooked at, what the food is cooked in, and how it is prepared before cooking.
The foods lowest in AGEs, as measured by the CML test, are most beverages, such as tea, coffee, and nonfat milk. Next lowest are most vegetables and fruits, followed by some grains and grain products. The highest are most meats and oils.
This may seem strange since there are minimal to no sugars in meat and oils. But the main test for AGEs has cross reactivity with ALEs. ALEs may contribute to the high values of meats and oils. Since this test for AGEs has shown that high levels of AGEs in our blood are bad for our health, it makes sense to use it to measure AGEs in food. But the research is early and much more work needs to be done before using AGE level as anything but a rough guide.
How Cooking Affects AGE
The three factors that change the AGE level in food are cooking temperature, food preparation, and cooking method.
The higher the temperature of cooking, the more AGEs are formed. Several studies have shown this relation to temperature. In this table we included the temperature in some of the foods, for example scrambled eggs, so you can compare. Of course, some food needs to be cooked to be safe from bacterial and parasite involvement. But once the temperature reaches that level it does not have to go higher. Generally, lower temperature and slower cooking is better.
The preparation before cooking can affect AGEs greatly. Adding lemon or lime juice or vinegar as a marinade can reduce the AGEs that form by interfering with the chemical bonding between the amino acid and the sugar or fat. Some foods are included that have been marinated, such as ground beef and chicken.
The final factor is what method is used to cook the food. The two major types of methods are dry and wet. Dry methods do not put the food in contact with hot water. The different types of cooking are none (raw), steaming, boiling, stewing, poaching, microwaving, baking, roasting, broiling, grilling, and frying, including pan-fried, stir-fried and deep fried. The first methods mentioned are wet methods and those mentioned after microwaving are dry methods. We won't explain what each of these methods entails. There is a good chart explaining cooking methods here.
Method Adding Most AGEs
Frying increases AGEs most. It entails cooking in fat. It may be the fat that drips off the food or it may be cooked on a surface of added fat or immersed in fat. Cooking in fat allows more fat (lipid) to combine with the amino acids.
Adding fat worsens the AGE level. Cooking meat or other foods with fat in its various forms markedly increases AGES. For comparison of different fats, eggs that have been cooked in different fats are in the table. Notice that different heat levels put the cooking fats in a different order.
Method Adding Least AGEs
Eating raw foods results in the least amount of AGEs. This is possible with many fruits, vegetables, nuts and seeds. These foods are mostly low in AGEs, so that even if some of the dry cooking methods are used, not much is added to the AGE level. Your daily total of AGE intake is not affected much.
Low heat, such as used in pasteurization, also does not add much to the AGE level. Liquids such as milk or yogurt are low in AGEs. Removal of water, though, as is done with cheese, increases the AGE level. Many cheeses have extremely high levels.
Steaming adds water to the cooking process. The temperature of the water does not get above 212 degrees unless in a pressure cooker. The lower temperature results in a slower reaction of sugar or fat with amino acid.
Microwaving cooks food by heating the water in the food itself or by heating water added externally to the food. This makes it a method similar to steaming. Because it does not rely on penetration of the food by the heated water, it is quicker than steaming.
Other methods that involve using heated water, such as boiling or stewing, perform like steaming also, but they also leach potassium from the food, which is a disadvantage for those who do not get enough potassium in their diet. A good way around the potential potassium loss is to consume the liquid, as is usual with a stew, soup or chili.
Baking, roasting, broiling, and grilling do not add water or use heated water, but instead remove water from the food by evaporation. The higher the temperature, the quicker the water removal and the quicker and more extensively the sugar and amino acid combine.
Table Of Selected Foods
In the table we have included examples of the effects of each of these cooking methods so you can compare and decide what methods are worth the trade off. You cannot eliminate AGEs in your diet, but you can reduce them by choosing what you eat and how you prepare it. For tables of high potassium foods and low potassium foods go to the list of posts page to locate foods by food groups.
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1. Advanced glycation end products in foods and a practical guide to their reduction in the diet. Uribarri J, Woodruff S, Goodman S, Cai W, Chen X, Pyzik R, Yong A, Striker GE, Vlassara H. J Am Diet Assoc. 2010 Jun;110(6):911-16.e12. PMID: 20497781