What Is the Cross-Linking Theory of Aging?

How Sugar Makes Us Age

A senior couple living in a nursing home.
A senior couple living in a nursing home.. FangXiaNuo/Getty Images

Did you know that your sweet tooth could make you age faster? Here's what you need to know about a process called the cross-linking theory of aging— and how sugar makes us age.

What Is Cross-Linking?

When you heat onions or toast bread, the sugar molecules in the foods bond to protein molecules. This bonding, which in cooking is called caramelization, is a result of the sugar molecules attaching to protein molecules.

When this happens, a series of reactions occur, called glycation, that result in protein molecules bonding to each other.

This cross-linking theory is the idea that chemical changes like this happen in your body and can lead to aging. The process is slow and complicated, but over time, more and more proteins, DNA and other structural molecules in the body develop inappropriate attachments, called cross-links, to one another. These cross-linked molecules don't function properly, and when enough cross-linked molecules accumulate in a specific tissue — such as cartilage, lungs, arteries and tendons — it can cause problems.

Results of Cross-Linking

When cross-linking occurs, tissues become stiffer, and when tissues stiffen they don't function as efficiently. Many of the symptoms of aging have to do with the stiffening of tissues. Cataracts, for example, are a stiffening of your eyes' lenses. Cross-linking of skin protein collagen has been found to be partially responsible for wrinkles and other age-related skin changes, and researchers believe that cross-linking of protein the walls of the arteries account for atherosclerosis, or the hardening of arteries that increases your risk for heart attack and stroke, among other conditions.

In addition, cross-linking of brain proteins occurs naturally with age, supporting the cross-linking theory of aging.

Slow It Down

While you can't stop cross-linking, you can slow it down. Researchers believe that if the concentration of sugar in the blood is high, then more cross-linking occurs. Foods with a high glycemic index, such as sugary sodas and juices, release sugar into the body quickly.

These foods have been associated with cardiovascular disease, possibly because of protein cross-linking. Everyone could benefit from keeping their blood sugar from spiking. And it could keep you looking and feeling young!


Aging Under the Microscope; National Institutes of Health, National Institute of Aging.

American Federation of Aging Research. (2011). Theories of Aging. Retrieved February 12, 2016.

Sugar and Cardiovascular Disease. Circulation. 2002;106:523.

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