AGEs are present in virtually all foods, even the high potassium foods. When advanced glycation end products (AGEs) occur in our bodies they contribute to many of the signs of aging, and appear to contribute to several diseases. How much AGEs (and ALEs, advanced lipoxidation end products) in our food contribute to AGEs in our bodies is being studied more and more. The research is too early to make any strong statements, though.
Old View Of AGEs
In the past a sign of AGEs being formed in food was the browning of food that occurs with cooking. However as methods have developed to measure some of the AGEs, simple browning has not proved as reliable as once thought. Using browning as an indicator, raw meat would be thought low in AGEs and bread crust would be thought high. But raw meat is much higher, and cooked meat higher still, using one of the most common methods of determining levels of AGEs.
In fact many of the prior ideas about AGEs are changing. The earlier idea that AGES were not absorbed has been found false. About 30% of the AGEs produced in a meal are absorbed.
Meats were thought to produce AGEs when combined with sugar in the cooking process, but they have been found to have AGEs even before cooking. Vegetables, fruits, and grains have sugar and protein. So they were thought to produce a large amount of AGEs with cooking. They do produce AGEs with cooking, but the amount is much lower than previously thought.
Maillard Reaction Is Not Just From Cooking
The Maillard reaction is the reaction that leads to the browning of food. It is a direct reaction between an amino acid and a reducing sugar.
The earliest discovery that the Maillard reaction occurs in the human body was the discovery of HbA1c in the 1960s. The test for HbA1c has been a major discovery. It has made the management of diabetes much better for doctors.
Before the discovery of HbA1c, the crosslinking that occurs in proteins in our bodies from sugar and amino acids was thought to be only by the indirect action of enzymes. When HbA1c was shown to be from the Maillard reaction, it started research into other places in the body that the reaction occurs. Even though it has been more than 40 years since the HbA1c discovery, only recently has the amount of research concerning AGEs in food begun to rapidly expand.
There are many different AGEs that form in the body, such as glucosepane, argpyrimidine, and pentosidine, with the most common being glucosepane. Many are derived from carboxymethyllysine (CML) and methylglyoxal (MG). Levels of CML and MG in the blood have been shown to correlate with the amount of AGE formation in our bodies.
Measuring CML and MG with their immunoassays has become the major way of determining AGEs. They have been used extensively to measure levels in the bloodstream. Recently they have been used to measure the level of AGEs in over 500 foods. Some of the results are surprisingly different than what you would think if you used the old way of thinking about AGEs.
There is more to AGEs than the browning of food. Cooking with dry heat does increase the dietary AGEs in a food, but the differences in AGE level in various uncooked foods is striking.
Some of the unexpected results may be due to the cross reaction between ALEs and AGEs in the immunoassays. But both AGEs and ALEs cause damage to our tissues, so how much cross reaction is present may not be important.
Although you shouldn't base your choice of foods only on the amount of AGEs in the food, it can be used as a tentative guide. It can help you choose some foods and some methods of preparation.
Next time we will provide a link to a table of foods with their AGE values. The post after that we will discuss some ways to reduce dietary AGEs by changing the cooking process.