Oxidative stress: causes, effects, prevention

Think back to a time when you were in school, and your teacher said, “Time to break off into groups!” Do you remember the chaotic hustle that followed as you tried to find your friends to make sure you weren’t left standing alone, stressed, without a group? 

Your body experiences something called oxidative stress when it’s faced with a somewhat similar situation. Let’s dive more into this analogy so you can get a better understanding of what oxidative stress is, what causes it, and how you can prevent it. 

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Oxidative stress occurs when there’s an imbalance between free radicals and the body's ability to fight them with antioxidants (more on that later). In order to understand this concept, we first have to explain what free radicals are. 

Free radicals are molecules that contain oxygen (most of the time) and have an odd number of electrons, making them unstable and destructive (Lobo, 2010). Using our group analogy above, just like you may feel stress being left without a partner or group, molecules in your body don’t like it when their electrons are unpaired. 

But they don’t suck it up and do the group projects with one less participant. They go scavenging to seek out and bind electrons from other groups (i.e., molecules), causing a negative chain of events along the way. In the body, that process of reacting with other molecules can damage our cells. 

To counter the potential damage from these free radicals, the body relies on antioxidants—molecules that can donate an electron to a raging free radical and neutralize it. And to go back to our analogy one last time, antioxidants are groups that either give or take a member, so nobody is alone. 

Some free radicals are formed naturally when you breathe, digest food, or when your body turns the food you eat into energy. This is normal and healthy. However, other exposures and lifestyle factors can also increase the formation of free radicals, including (Sharifi-Rad, 2020; Pizzino, 2017):

• Ultraviolet radiation from sun exposure or tanning beds

• Cigarette smoking and secondhand exposure

• Alcohol

• Pollutants

• Drugs, chemicals, and pesticides

• Too little or too much exercise (overtraining)

• Diets high in sugar or fat (Poljsak, 2011)

When there are more free radicals than antioxidants, the free radicals can damage things like DNA, fatty tissues, and proteins in the body (Sharifi-Rad, 2020). 

Over time, uncontrolled oxidative stress may contribute to (Pizzino, 2017; Sharifi-Rad, 2020):

• Atherosclerosis, or the hardening of the blood vessels (this can lead to cardiovascular disease)

• Inflammatory disorders like Rheumatoid Arthritis

• Kidney disease

• Cancer

• Diabetes

• Neurodegenerative diseases like Parkinson’s disease and Alzheimer’s disease

• Speeding up the aging process (Tan, 2018)

The body defends against free radicals through its antioxidant system. Antioxidants are compounds that fight free radicals by preventing or slowing the chain of events that leads to oxidative stress. 

Before jumping into this, it’s important to understand that increasing your intake of antioxidants—in your diet or supplements—isn’t enough to outweigh the impacts of free radicals. 

In other words: antioxidants are not a free radical hall pass. Smoking, alcohol, and processed foods still increase the risk of certain diseases (like cancer and cardiovascular disease), even if you eat antioxidant-rich foods.       

Here’s what you can do to ward off oxidative stress: 

Eat an antioxidant-rich diet

Support your body’s antioxidant defense mechanisms by eating foods rich in antioxidants. These dietary antioxidants include (Sharifi-Rad, 2020): 

• Vitamin C: citrus fruits, bell peppers, strawberries, spinach

• Vitamin E: nuts, seeds, broccoli, fatty fish 

• Phytonutrients (beneficial plant compounds like flavonoids and carotenoids)

• Flavonoids: green tea, cocoa, turmeric

• Carotenoids: red, orange, and yellow fruits and vegetables 

• Zinc: oysters, crab, pumpkin seeds

• Selenium: Brazil nuts, tuna, sardines 

Studies indicate that plant-based diets are linked to lower levels of oxidative damage and inflammation, which helps reduce the risk for chronic disease. For example, the Mediterranean diet—rich in fruits and vegetables—can reduce DNA damage and is anti-inflammatory, whereas Western diets—high in refined carbohydrates, saturated fats, and salt—promote inflammation (Aleksandrova, 2021). 

With that said, while research shows that antioxidant-rich diets (like the Mediterranean diet) can protect against oxidative stress and inflammation, antioxidant supplements don’t appear to have the same effect (Sharifi-Rad, 2020). 

Wear sunscreen

Ultraviolet radiation from the sun (sunburns) increases oxidative stress in skin cells. This can lead to skin cancer (de Jager, 2017). The American Academy of Dermatology recommends that you use sunscreen (SPF 30 or higher) every day if you will be outside, and reapply every two hours if you’re out in the sun for an extended time (AAD, n.d.). 

Don’t smoke and avoid exposure to smoke

Smoking cigarettes is a known producer of free radicals and oxidative stress that is directly linked to the development of lung cancer. Secondhand smoke also exposes you to the same toxins. Avoiding smoke and secondhand exposure to it reduces your chances of oxidative stress and chronic disease (Walser, 2008). 

Engage in physical activity 

Intense exercise can trigger free radical production and oxidative stress. However, regular exercise is linked with lower levels of inflammation and chronic disease. It’s recommended to get at least 150 minutes of moderate-intensity exercise in a week to promote health. For competitive athletes that often train at high volumes, remember to take rest days to help your body recover (HHS, 2018; Sallam, 2016). 

Be mindful of alcohol consumption

When alcohol is broken down in the liver, molecules are formed that are then converted to free radicals. So increased alcohol consumption means increased free radical formation. Try to keep your alcohol intake at a low to moderate level. Moderate alcohol consumption is defined as two drinks a day for men and one for women (Wu, 2003).

We’re exposed to things that lead to oxidative stress daily. Prolonged and high levels of oxidative stress can damage our cells, including our DNA. And while oxidative stress is a balancing act, the equation isn’t as simple as increased antioxidants decrease free radicals, equaling less oxidative stress. 

Free radical production and oxidative stress are influenced by so many lifestyle habits, including diet, exposure to toxins and chemicals, sunlight, smoking, and exercise. Reducing oxidative stress and the risk of diseases associated with it requires a holistic approach across all of your daily habits so that you can address supporting your body’s antioxidant defenses while minimizing your exposure to free radical triggers. 

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

December 13, 2021

Written by

Molly Knudsen, MS, RDN

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.