Oxidative stress is an imbalance of free radicals and antioxidants in the body, which can lead to cell and tissue damage. Oxidative stress occurs naturally and plays a role in the aging process.
A large body of scientific evidence suggests that long-term oxidative stress contributes to the development in a range of chronic conditions. Such conditions include cancer, diabetes, and heart disease.
What is oxidative stress?
Many lifestyle factors can contribute to oxidative stress.
Oxidative stress can occur when there is an imbalance of free radicals and antioxidants in the body.
The body’s cells produce free radicals during normal metabolic processes. However, cells also produce antioxidants that neutralize these free radicals. In general, the body is able to maintain a balance between antioxidants and free radicals.
Several factors contribute to oxidative stress and excess free radical production. These factors can include:
- Certain conditions
- Environmental factors such as pollution and radiation
The body’s natural immune response can also trigger oxidative stress temporarily. This type of oxidative stress causes mild inflammation that goes away after the immune system fights off an infection or repairs an injury.
Uncontrolled oxidative stress can accelerate the aging process and may contribute to the development of a number of conditions.
What are free radicals?
Free radicals, including reactive oxygen species, are molecules with one or more unpaired electrons. Examples of free radicals include:
- Hydroxyl radical
- Nitric oxide radical
Cells contain small structures called mitochondria, which work to generate energy in the form of adenosine triphosphate (ATP).
Mitochondria combine oxygen and glucose to produce carbon dioxide, water, and ATP. Free radicals arise as byproducts of this metabolic process.
External substances, such as cigarette smoke, pesticides, and ozone, can also cause the formation of free radicals in the body.
What are antioxidants?
Fresh berries and other fruits contain antioxidants.
Antioxidants are substances that neutralize or remove free radicals by donating an electron. The neutralizing effect of antioxidants helps protect the body from oxidative stress. Examples of antioxidants include vitamins A, C, and E.
Like free radicals, antioxidants come from several different sources. Cells naturally produce antioxidants such as glutathione.
A person’s diet is also an important source of antioxidants. Foods such as fruits and vegetables provide many essential antioxidants in the form of vitamins and minerals that the body cannot create on its own.
Effects of oxidative stress
The effects of oxidative stress vary and are not always harmful. For example, oxidative stress that results from physical activity may have beneficial, regulatory effects on the body.
Exercise increases free radical formation, which can cause temporary oxidative stress in the muscles. However, the free radicals formed during physical activity regulate tissue growth and stimulate the production of antioxidants.
Mild oxidative stress may also protect the body from infection and diseases. In a 2015 study, scientists found that oxidative stress limited the spread of melanoma cancer cells in mice.
However, long-term oxidative stress damages the body’s cells, proteins, and DNA. This can contribute to aging and may play an important role in the development of a range of conditions.
We discuss some of these conditions below:
Oxidative stress can cause chronic inflammation.
Infections and injuries trigger the body’s immune response. Immune cells called macrophages produce free radicals while fighting off invading germs. These free radicals can damage healthy cells, leading to inflammation.
Under normal circumstances, inflammation goes away after the immune system eliminates the infection or repairs the damaged tissue.
However, oxidative stress can also trigger the inflammatory response, which, in turn, produces more free radicals that can lead to further oxidative stress, creating a cycle.
Chronic inflammation due to oxidative stress may lead to several conditions, including diabetes, cardiovascular disease, and arthritis.
The effects of oxidative stress may contribute to several neurodegenerative conditions, such as Alzheimer’s disease and Parkinson’s disease.
The brain is particularly vulnerable to oxidative stress because brain cells require a substantial amount of oxygen. According to a 2018 review, the brain consumes 20 percent of the total amount of oxygen the body needs to fuel itself.
Brain cells use oxygen to perform intense metabolic activities that generate free radicals. These free radicals help support brain cell growth, neuroplasticity, and cognitive functioning.
During oxidative stress, excess free radicals can damage structures inside brain cells and even cause cell death, which may increase the risk of Parkinson’s disease.
Oxidative stress also alters essential proteins, such as amyloid-beta peptides. According to one 2018 systematic review, oxidative stress may modify these peptides in a way that contributes to the accumulation of amyloid plaques in the brain. This is a key marker of Alzheimer’s disease.
Conditions linked to oxidative stress
Oxidative stress may play a role in the development of a range of conditions, including:
- Alzheimer’s disease
- Parkinson’s disease
- Cardiovascular conditions such as high blood pressure, atherosclerosis, and stroke
- Inflammatory disorders
- Chronic fatigue syndrome
- Male infertility
Risk factors for oxidative stress
Pollution can increase the risk of long-term oxidative stress.
Factors that may increase a person’s risk of long-term oxidative stress include:
- Diets high in fat, sugar, and processed foods
- Exposure to radiation
- Smoking cigarettes or other tobacco products
- Alcohol consumption
- Certain medications
- Exposure to pesticides or industrial chemicals
It is important to remember that the body requires both free radicals and antioxidants. Having too many or too few of either may lead to health problems.
Lifestyle and dietary measures that may help reduce oxidative stress in the body include:
- Eating a balanced, healthful diet rich in fruits and vegetables
- Limiting the intake of processed foods, particularly those high in sugars and fats
- Exercising regularly
- Quitting smoking
- Reducing stress
- Avoiding or reducing exposure to pollution and harsh chemicals
Maintaining a healthy body weight may help reduce oxidative stress. According to a 2015 systematic review, excess fat cells produce inflammatory substances that trigger increased inflammatory activity and free radical production in immune cells.