What Is a Free Radical?

Free radicals are highly unstable, reactive molecules in your body. Your body has antioxidants to help neutralize them.

Small amounts of free radicals help your body with some of its processes. However, if there are too many free radicals for antioxidants to defend against, they can build up in your body. This can harm your DNA and cells, leading to diseases.

Free radicals are highly unstable molecules with unpaired electrons (negatively charged particles within an atom, the basic unit of matter). They seek an electron to become stable.

To do so, they may bond with or steal electrons from other molecules in your cells, such as DNA, proteins, or lipids (fats). This can change the structure of these other molecules, damaging them. Damage to these molecules can lead to inflammation, aging, and diseases.

Free radicals may come from internal and external sources. They vary in type and reactivity. Some are potentially more harmful than others. The most reactive free radicals are called reactive oxygen species (ROS), which come from oxygen.

Your body produces free radicals as a normal part of helping with some bodily functions. For example, your immune system (your body’s defenses) uses free radicals to kill germs.

Sometimes, though, free radicals may outpace your body’s ability to use and get rid of them. This imbalance results in oxidative stress, which can cause tissue damage and contribute to several diseases. Oxidizing is a chemical process in which a molecule loses an electron.

Cardiovascular Diseases

Healthy blood vessels are vital for a healthy heart. Atherosclerosis (a disease where fat builds up within blood vessels, narrowing them) is the main cause of heart disease.

Oxidative stress is one contributor to this disease. Free radicals play a role in oxidizing low-density lipoprotein (LDL, or “bad”) cholesterol. Oxidized LDL triggers an immune response that changes the LDL molecules, which build up and narrow blood vessels.

Neurodegenerative Diseases

Oxidative stress can lead to neurological diseases, such as memory loss, Parkinson’s disease, and Alzheimer’s disease.

For example, Parkinson’s disease is caused by a loss of neurons (nerve cells) called dopaminergic neurons. Scientists believe oxidative stress causes this loss. It damages the DNA, lipids, and proteins of the neurons. It also disrupts their repair system.

In Alzheimer’s disease, certain proteins accumulate in the brain. This buildup is thought to increase oxidative stress and contribute to brain cell damage.

Skin Diseases

The sun is a major source of ultraviolet radiation, exposure to which can create free radicals. You need sunlight, but too much ultraviolet radiation can burn your skin. The damage is oxidative stress, which ages your skin and can lead to various conditions, including skin cancer and psoriasis.

Diabetes 

Oxidative stress is linked to diabetes and its complications, like nerve, eye, and kidney damage. High blood sugar levels increase the production of certain molecules that cause oxidative stress. The increased free radicals can also damage your pancreas (the organ that secretes insulin and other hormones), further disrupting insulin production.

Cancer 

Free radicals not only damage cell components but also your genetic material. When free radicals damage your DNA, it can lead to the development of cancer.

Other Diseases

Many other diseases stem from chronic inflammation due to oxidative stress. These include:

Free radicals may come from internal and external sources.

Internal Sources

Your body regularly produces free radicals through several processes. These include:

• Energy production: Metabolism (the chemical process that turns food into energy) naturally produces free radicals. 
• Immune response: Some immune cells make free radicals and use them to kill germs and clear up inflammation.
• Exercise: Exercise can lead to the production of free radicals; it’s one of the reasons you may be fatigued after intense exercise. Exercise-induced oxidative stress can affect your health positively or negatively, depending on the type, intensity, and duration of the exercise. Individual differences also matter.

External Sources

Many external sources contribute to free radical production. These include:

• Environmental pollution: Air, soil, and water pollution can increase oxidative stress. For example, air pollution is linked to higher oxidative stress in people with respiratory issues.
• Heavy metals: Heavy metals (like lead, mercury, and arsenic) can sometimes contaminate the air, soil, and water. They’re toxic to your cells and increase oxidative stress in your body, which further increases the immune cells’ production of free radicals.
• Smoking: Tobacco smoke contains many harmful chemicals that activate the inflammatory response. This causes immune cells to create free radicals.
• Medications: Some drugs can increase oxidative stress by producing free radicals or suppressing the body’s antioxidants. This includes some cancer drugs, nonsteroidal anti-inflammatory drugs (NSAIDs), and painkillers, among others.
• Pesticides: Pesticides are chemicals that kill pests. They are used in farming and other areas to protect food, homes, and gardens. Exposure can increase oxidative stress, and continuous or high doses of exposure are likely to cause health problems.
• Ionizing radiation: The two main types of radiation are non-ionizing (like microwave radiation, which is generally safe) and ionizing. Ionizing radiation can remove electrons from atoms or molecules, making them unstable and reactive. This type of radiation is powerful and can cause cell death. You may be exposed if you come into contact with certain elements, like uranium, or radiation from cancer treatments.

Antioxidants are substances that protect us from free radicals. They do this by donating electrons to free radicals, making them stable so they are no longer damaging to cells. 

Your body makes some antioxidants, such as enzymes (proteins that speed up reactions), certain molecules, and nutrients. Other antioxidants must come from your diet. These include:

• Vitamins A, C, and E
• Selenium
• Zinc
• Phytochemicals, which are plant compounds found in fruits, vegetables, whole grains, legumes, herbs, and spices

Research on whether antioxidant supplements can help prevent or treat cancer and other diseases is mixed. However, some research suggests that eating foods high in antioxidants lowers the risk of chronic diseases.

Scientists think the difference may be due to the source and dosage of the antioxidant. These nutrients work differently as supplements compared to when they are part of whole foods. Eating foods high in antioxidants can help support your body’s antioxidant system.

Free radicals are unstable molecules that can harm your body. Your body produces free radicals that, in small amounts, can help with bodily functions. However, exposure to toxins, radiation, and other substances can lead to too many free radicals, making them harmful.

Free radicals may contribute to diseases like cancer, metabolic disorders, heart disease, and autoimmune disease. Antioxidants are molecules that help get rid of free radicals. Consuming antioxidant-rich foods may help lower your risk of chronic diseases.