How do free radicals affect the body?

Free radicals are unstable atoms that can damage cells, causing illness and aging.

Free radicals are linked to aging and a host of diseases, but little is known about their role in human health, or how to prevent them from making people sick.

What are free radicals?

Young woman and older woman with faces side by side.
Free radicals are thought to be responsible for age-related changes in appearance, such as wrinkles and gray hair.

Understanding free radicals requires a basic knowledge of chemistry.

Atoms are surrounded by electrons that orbit the atom in layers called shells. Each shell needs to be filled by a set number of electrons. When a shell is full; electrons begin filling the next shell.

If an atom has an outer shell that is not full, it may bond with another atom, using the electrons to complete its outer shell. These types of atoms are known as free radicals.

Atoms with a full outer shell are stable, but free radicals are unstable and in an effort to make up the number of electrons in their outer shell, they react quickly with other substances.

When oxygen molecules split into single atoms that have unpaired electrons, they become unstable free radicals that seek other atoms or molecules to bond to. If this continues to happen, it begins a process called oxidative stress.

Oxidative stress can damage the body's cells, leading to a range of diseases and causes symptoms of aging, such as wrinkles.

How do free radicals damage the body?

Free radicals.
Free radicals are unstable atoms. To become more stable, they take electrons from other atoms. This may cause diseases or signs of aging.

According to the free radical theory of aging, first outlined in 1956, free radicals break cells down over time.

As the body ages, it loses its ability to fight the effects of free radicals. The result is more free radicals, more oxidative stress, and more damage to cells, which leads to degenerative processes, as well as "normal" aging.

Various studies and theories have connected oxidative stress due to free radicals to:

The free radical theory of aging is relatively new, but numerous studies support it. Studies on rats, for example, showed significant increases in free radicals as the rats aged. These changes matched up with age-related declines in health.

Over time, researchers have tweaked the free radical theory of aging to focus on the mitochondria. Mitochondria are tiny organelles in cells that process nutrients to power the cell.

Research on rats suggests that free radicals produced in the mitochondria damage the substances that the cell needs to work properly. This damage causes mutations that produce more free radicals, thus accelerating the process of damage to the cell.

This theory helps explain aging, since aging accelerates over time. The gradual, but increasingly rapid buildup of free radicals offers one explanation for why even healthy bodies age and deteriorate over time.