Thursday, July 9, 2009

How 'age' (instead of 'old') are you?

The Maillard Reaction

Here is a summary of some articles I read in the internet. One written by Will Block: How and why to prevent AGE damage, is recommended for your reading.

In 1912, Louis Camille Maillard, a French physician and chemist, investigated what happened when sugars (such as glucose and fructose) were combined with amino acids, the building blocks of proteins.

Maillard heated aqueous (water) solutions of sugars and amino acids for a few hours. They turned into a yellow-brown color, the result of a series of reactions that yielded a brew of products collectively called AGEs, advanced glycation end-products.

AGEs are implicated in the development or exacerbation of numerous degenerative diseases associated with aging, notably type 2 diabetes, atherosclerosis, cardiovascular disease, Alzheimer’s and other dementias, cataracts, retinal dysfunction, kidney failure, nerve damage, arthritis, and cancer.

Most AGEs Are Yummy

If you’re the kind of person who likes food, you would probably love dietary AGEs because they happen to be among the tastiest compounds known. They are responsible for many colors and flavors in foods. They form the brown crusts of bakery products, biscuits, roasted coffee, malted barley as in malt whiskey or beer, and in meats or vegetables that have been baked, roasted, broiled, grilled, fried, sautéed, etc. Many AGEs are found in commercial food flavorings designed to make all kinds of foods taste even better, as though they’d been browned. In fact, the Maillard reactions form the basis of the flavoring industry and are portrayed in a good light because of the gustatory wonders they produce. Chefs love them.

AGEs In the Body

The Maillard reaction also occurs in the human body. It is a step in the formation of AGES, advanced glycation end-products.

In 1971, scientists investigating the blood of diabetic patients discovered that some of the hemoglobin was glycated. Glycation is the first step in the Maillard reactions. In this reaction a sugar molecule is attached to an amino acid. As the ensuing reactions advance through numerous complex stages, they can lead to formation of a great variety of end-products, collectively known as AGEs, most of which are harmful to us. AGEs are the caramel-like sticky substances that get jammed within and between our cells and contribute to feeling old and tiredness.
The sugar of greatest importance to us is glucose. Fortunately, glucose is among the least reactive of the nutrient sugars in the Maillard reactions. The glycation reactivity of fructose (fruit sugar) is about ten times higher than that of glucose. Unlike most biologically important reactions, which are catalyzed by enzymes, glycation is not catalyzed. The lack of enzymatic control over the glycation process means that this reaction can occur haphazardly—anytime, anywhere, to an extent limited only by the availability of the reactants. Thus there’s nothing to restrain glucose from reacting with amino acids and proteins, which are everywhere in the body. Since we can’t live without glucose, we can’t avoid AGEs—but we can slow down their formation.

The Maillard Reaction happens within our bodies when certain conditions exist. The most common trigger for this is high blood sugar.

v High blood sugar exists in the following conditions: diabetes (both types), when eating more carbohydrates than our metabolism can handle.

v In the initial phase of hypoglycemia when our blood sugar spikes before dropping too low to deal with this elevated sugar in our blood, our body uses the Maillard Reaction to "cook" the sugar down into AGE.
Dietary Sources of AGE

The other source of AGE is our diet. Some foods are naturally high in AGE. Others create AGE when they are prepared in certain ways. Foods that are high in AGE are:

pasteurized milk, chocolate, margarine, sugar and other concentrated sweeteners, white flour (bread, bagels, cookies, cakes, etc.), regular salt (unrefined sea salt is okay). In addition, foods cooked over 112° F typically contain AGE. The higher the cooking temperature is the more AGEs are being created.

AGEs Come in Large and Small Sizes

There are hundreds of known AGEs produced by the Maillard reactions in our bodies. Some of these are very large molecules produced by the chemical linkage between sugars and proteins that were never intended to be linked. As a result of such cross-linking loss of tissue elasticity can occur in the heart, blood vessels, skin, eyes, kidneys, joints, etc. We see such problems in elderly people.

Many other AGEs are relatively small degradation products of the Maillard reactions, and some of these contain a reactive chemical group called the carbonyl group. The spectrum of damage caused by carbonyl compounds is called carbonyl stress. It’s analogous to the oxidative stress caused by reactive oxygen species, including free radicals.

AGEs can also be formed by the reactions of sugars (or other reactive carbonyl compounds) with lipids (fats) and nucleic acids (DNA and RNA). These AGEs too are deleterious to our health.

How To Avoid AGE
Here are some tips to help us avoid AGE:

* Reduce or eliminate refined, simple sugars in your diet. This will reduce the high blood sugar spikes that can trigger AGE formation.
* Reduce or eliminate refined grains (especially white flour), and the products made from them.
* Chew our food thoroughly. This reduces the effects of AGE in our foods.
* Avoid charred, fried, pasteurized, dried and processed foods. Many prepared foods have been exposed to high temperatures to lengthen shelf life, so they may have high AGE contents.
* Eat more raw and lightly cooked foods. By eating raw vegetables and lightly cooked meats, the enzyme levels are higher and you don't draw on your body's own enzymes as much. Do this by preparing your foods the following ways: light steaming, baking, stewing, stir-frying and slow crock cooking.
* Eat enough fresh vegetables and fruits.

Unfortunately, our body’s mechanisms for removing waste products cannot keep up with the production of AGEs. And also AGEs are resistant to this elimination process.

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