© 2010 Nancy Appleton PhD and G.N. Jacobs
The bird or ham turns brown fat dripping into the bottom of the pan. The family gathers to eat and give thanks and gifts, but how healthy are the various cooking methods anyway? Well, the answer depends on what you cook and how you cook it, because I’m sure this is the first time you heard of Advanced Glycated End Products (AGEs).
What is an AGE? AGEs were discovered by Louis Maillard in 1912. Simply put they are a class of chemical byproducts that result from the meeting of food and excessive heat. Protein and a sugar (usually glucose) combine under high heat to create the browning that we associate with cooking.[i] Or you could just eat too much sugar and maintain elevated blood sugar levels for too long. Excessive sugar helps to form AGEs in the body because the sugar has to go somewhere.
So what is so bad about AGEs? Generally, the body evolved to eat food cooked slowly over a small open flame or raw compared to flash heating, microwaving, deep-frying and barbecuing. The AGEs that form, with these cooking methods, are toxic to the body and aren’t easily metabolized out of the body. When the body deals with foods that aren’t exactly like what it expects to find the immune system is called in to smash an invader. Our immune system can only do so much becoming exhausted further dragging down the removal process. Eventually, an allergy may form that may lead to disease. Unfortunately, AGEs taste great being sugar and protein jumbled together explaining why we like toast, ribs and blackened fish so much.
AGEs aren’t to be confused with glycoproteins, even though they share the same building blocks. A glycoprotein forms when glucose and proteins bind using the normal digestive enzymes with which we all come equipped. This process presupposes gently cooked food and moderate sugar intake from whole fruits and vegetables and very little (preferably none) refined sugar. Glycoproteins are part of how the body feeds itself. AGEs are something else entirely.
Not all cooking methods are created equal. Studies have shown that boiling, steaming, or any method involving water tends to limit greatly the number of AGEs that form. Turning down the heat and extending the cooking time can also create fewer AGEs than other methods. There are two different temperature ranges to be aware of: the heat labile point around 245° F and the much lower AGEs threshold between 120° F and 180° F. The heat labile point applies to fats and proteins that change chemically without the presence of sugar and has similar health risk as the AGEs discussed here.
Recently, studies have shown that green tea helps prevent formation of AGEs and many of the diseases they cause.[ii] We should also avoid processed foods. Food manufacturers increase the number of AGEs in food intentionally, either by adding sugar or by browning food elements. They are trading on the great taste of browned or caramelized food to sell more units. You are warned.
WHAT TO DO TO AVOID AGES
- Turn down the heat and extend the cooking time
- Stop eating sugar
- Cook with water (boil, steam and poach) as much as possible
- Green tea may prevent AGEs
- Avoid processed foods which are likely to have sugar or browned food elements
AGEs have become a worry now in the modern era compared to more primitive times because of several factors, including excessive sugar consumption. We have said above that our high sugar usage can induce the body to make its own AGEs regardless of how the food was cooked. We have quoted figures previously that the average American eats at least 140 pounds of sugar per year.[iii] Along with the other ways sugar hurts us (insulin resistance, etc.) these AGEs that are very nearly indestructible once created and deposited in the body also help cause many diseases.
AGEs spur the release of cytokines, which are part of the inflammatory process. Cytokines collect in the joints of people with arthritis. Another interesting fact about AGEs and inflammation is that free radical production is nearly five times greater with glycated protein compared to regular protein.[iv] We discuss these issues in more detail in our book Stopping Inflammation.
We will list below a small sample of diseases and conditions that can be helped by limiting AGEs either by changing how we cook or cutting out the sugar.
- Alzheimer’s disease[ix]
- Macular Degeneration[x]
- Kidney Disease[xiii]
This list is not inclusive, but is just enough for all of us to be mindful that how we cook our food is at least as important as what foods we eat. You’ll notice that we’ve said gently cooked versus raw. For many people the practice of cooking is so ingrained in human culture that eating raw food that we traditionally cook might cause a gag. In some cases, cooking is necessary for economic reasons like extending the shelf life of food. For example, toasting turns stale bread into toast, which tastes the same regardless of how fresh the bread was. Striking the balance between, killing off pathogens in poorly stored raw food and overcooking has always been delicate. Eating raw can help a person be healthier, but it can be a hard choice.
[i] Bjeldanes, L. “Effects of High Temperatures on Meats.” Food and Chemical Toxicology Apr 1985:23(12).
[ii] Rasheed, Z, et al. “Green Tea Polyphenol Epigallocatechin-3-Gallate Inhibits Advanced Glycation End Product-Induced Expression of Tunor Necrosis Factor-Alpha and Matrix Metalloproteinase-13 in Human Chondrocytes.” Arthritis Res Ther. May 2009;11(3):R71
[iv] Mullarkey, CJ., et al. “Free Radical Generation by Early Gycation Products: A Mechanism for Acceleration of Arthogenesis in Diabetes.” Biochem Biophys Res Commun Dec 31, 1990;173(3):932-939.
[v] Uribarri, J., et al. “Diet-Derived Advance Glycation End Products are Major Contributors to the Body’s AGE Pool and Induce Inflammation in Healthy Subjects.” Annals NY Acad Sci. 2005:461-466.
[vi] Semba, RD., et al. “Does Accumulation of Advanced Glycation End Products Contribute to the Aging Phenotype?” J Gerontol A Biol Sci Med Sci Apr 2010;65A(9):963-975.
[vii] Birlouez-Aragon, I., et al. “A Diet Based on High-Heat-Treated Foods Promotes Risk Factors for Diabetes Mellitus and Cardiovascular Diseases.” Am J Clin Nutr May 2010;91(5):1220-1226.
[viii] Peppa, M., et al. “Glucose, Advanced Glycation End Products and Diabetes Complications: What is New and What Works.” Clin Diabetes. 2003;21:186-187.
[ix] Tabaton, M., et al. “Is Amyloid Beta-protein Glycated in Alzheimer’s Disease?” Neuroreport. 1997;8(4):907-909.
[x] Ishibashi, T., et al. “Advanced Glycation End Products in Age-related Macular Degeneration.” Arch Ophthalmol. Dec 1998;116(12):1629-1632.
[xi] Szymanska, U. and Boratynski, J. “Protein Glycation-Clinical and Chemical Aspects.” Postepy Hig Med Dosw. 1999;53(5):689-703.
[xii] MacLennan, A., “Identification of the Advanced Glycation End Product N-Epsilon-Carboxymethyllysine in the Synovial Tissue of Patients with Rheumatoid Arthritis.” Annals of the Rheumatic Diseases (ARD Online). Sept 12, 2002.
[xiii] Dominic, SC., at al. “Advanced Glycation End Products: a Nephrologist’s Perspective.” Am J Kidney Dis. 2000;35(3):365-380.