AGEs (advanced glycation end products) are found in our body and in the food we eat. In our body AGEs contribute to the stiffening of tissues that occurs with age. Joints, blood vessels, the heart and lungs are some of the tissues of most concern, leading to decreased flexibility, higher than recommended blood pressure, cardiac insufficiency, and reduced breathing capacity.
Previously it was thought that AGEs in food were not absorbed. But now we know about 30% of the AGEs in food are absorbed, and elevated levels in our blood stream are associated with worse health. AGEs in food have been long known, and have been sought after by chefs. It gives the “browning” so often sought after.
However, the browning of certain foods does not raise the AGE level of the food very much, while some foods that are not “browned” have high levels to start with. And even the AGE level does not tell the whole story concerning the premature crosslinking in proteins that occurs in diabetics, one of Maillard's original hopes. High blood sugar is a big part of protein crosslinking in our bodies. But AGEs may help to explain some of the increased crosslinking even when the blood sugar has been closely controlled, or when the individual is not diabetic.
Tests For AGEs
The main tests for AGEs are the tests for carboxymethyllysine (CML) and methylglyoxal (MG). However these tests have cross reactivity with ALEs (advanced lipoxidation end-products), and for some foods the tests may be measuring ALEs more than AGEs. This may not matter, since ALEs may be as harmful as or even more harmful than AGEs. So CML levels may be more indicative of harm in our bodies than a pure test for AGEs that had no cross reactivity.
An extensive table of over 500 foods and their AGE content has been published recently. It is mostly designed for the use of researchers, but it can provide insight into the nature of AGEs for non-researchers.
Table Of CML Levels
For today's post we took a small sample from the larger table in this article (1). It measured the CML level in multiple common foods. The foods we chose were to point out the large differences between the AGE level in certain food groups that have “browning” and other food groups. The highest AGE levels are in those foods that have a high fat content, especially if there is a large combination of fat and protein, such as in bacon and beef.
“Browned” grain and other plant products are not as high, such as toast, pop tarts, pancakes and grilled vegetables. But products that are “browned” in fat are quite high, such as bacon, beef and french fries. Next post we will discuss how different methods of food preparation lead to different levels of AGEs in the same basic dish.
The AGE value is not the only or even the main consideration in choosing healthy foods. As mentioned in prior posts, the research on AGEs is in its early stages. But there are some high potassium foods that have high AGE levels. It may be wise to limit eating those foods, and get more of those low in AGE.
How food is prepared is very important in determining the AGE level of food. The original idea was that dry heat that leads to browning is the main factor in causing AGEs in food. Next post we will discuss the various methods of food preparation and how they influence AGE level.
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