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What is Oxidative Stress? Jeanne Rosner, MD

Updated: Apr 18, 2022

Have you ever wondered why apples or avocados turn brown a few minutes after you cut into them? Why do old cars start to rust? It’s thanks to a process called oxidation. When this same activity occurs in our bodies, it is referred to as oxidative stress. Over time, oxidative stress can be extremely harmful to the human body, leading to degenerative changes that accelerate aging and cause chronic disease. For true health to prevail, our goal should be to provide an environment where oxidative stress is minimized. Oxidation is the process of removing electrons from an atom or molecule. Electrons normally exist in pairs. When they fly solo, they are highly unstable or reactive; in this state, they are also known as reactive oxygen species (ROS) or free radicals. Damage occurs when the free radical encounters another molecule and seeks to find another electron to pair with to become more stable. The unpaired electron pulls an electron off a neighboring molecule (often the donor is DNA, important structural or functional proteins, LDL cholesterol particles, or even cell membranes) causing the affected molecule to behave like a free radical itself—and a chain reaction occurs. In their wake, the free radicals create even more unstable molecules that then attack their neighbors in a domino-like chain reaction. Not surprisingly, the end result of this process can be highly destructive.

The production of free radicals can occur as a normal byproduct of metabolism. It also results from exposure to things like certain chemicals, cigarette smoke, pollution, radiation, increased sunlight exposure and tanning beds. The simple loss of electrons can subtly alter the function of, or even damage, DNA, proteins and cell membranes. Cumulative damage of this sort probably accounts for premature aging, many of the degenerative changes of aging and age-related diseases such as cancer and cardiovascular disease. 

Antioxidants help stave off oxidative stress. They can donate electrons and stop the spiraling domino effect. Interestingly, antioxidants are able to give up electrons to free radicals without turning into electron-scavenging substances themselves.

In addition to the presence of antioxidants in our diet, we are fortunate that our body can defend against oxidative stress in many other ways. Within cells, there are physical barriers that can help contain free radicals at their site of production. Enzymes in the body can help neutralize the dangerously reactive forms of oxygen. Programmed cell death (apoptosis) can occur when damage becomes excessive. In general, however, when there are too many free radicals in the body and too few antioxidants and/or mechanisms to defend against oxidative stress, more damage occurs. As an example, free radicals can oxidize LDL cholesterol. When this happens, atherosclerotic plaques can form in blood vessel walls. Ultimately, this has the potential to lead to blood clots resulting in blood flow blockage in the heart and brain, causing a heart attack or stroke, respectively.

To help prevent an environment of oxidative stress, we should try to reduce free radical formation and help ensure an abundance of antioxidant support. The following are some tips to create this supportive environment.

1. Modify diet: Reduce consumption of trans fats, alcohol, high glucose-containing foods and fructose (not from fruit). These food items can overwhelm the metabolic capacity of the liver, resulting in free radical production. In addition, avoid deep-fried foods because they are notorious sources of free radicals, caused by the oil being continuously oxidized when it is heated at high temperatures.

2. Increase fiber intake: This helps reduce the rate at which the liver metabolizes energy; therefore it reduces the production of free radicals.

3. Increase antioxidant ingestion: Eat a diet full of fruits, vegetables, nuts and whole grains. The richer the color and more variety in these foods, the more nutrients and antioxidants they will provide. Each different color in fruits and vegetables represents a different nutrient and antioxidant. Research shows individual antioxidants in supplement form provide minimal benefit.

4. Increase mitochondrial formation and number through exercise. This allows better processing and metabolism of food items, thereby preventing the production of free radicals.

Trying to keep the “rust” out of our bodies is an important step in preventing the degenerative changes of aging as well as chronic diseases. To reduce your overall oxidative stress burden, make sure you’re eating a healthful diet, full of a wide variety of fruits and vegetables, and getting plenty of exercise.


Hyman, Mark. “Glutathione: The 'mother' of all antioxidants.”

Lobo, V. et al. “Free radicals, antioxidants and functional foods: Impact on human health.” Pharmacognosy Review. 2010 Jul-Dec; 4(8): 118–126. doi:  10.4103/0973-7847.70902.

Lustig, Robert. Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity and Disease. New York: Penguin, 2013. Print.

Uttara, Bayani et al. “Oxidative Stress and Neurodegenerative Diseases: A Review of Upstream and Downstream Antioxidant Therapeutic Options.” Current Neuropharmacology. 2009 Mar; 7(1): 65–74. doi:  10.2174/157015909787602823.

Jeanne Rosner, MD

Jeanne Rosner is a board-certified anesthesiologist who practiced pediatric anesthesia at Stanford Medical Center for nearly 20 years. In 2011, she began teaching nutrition classes in her son’s 5th-grade science class. It was an “aha” moment for her. She realized that learning and teaching about nutrition, health and wellness in her community was her destiny. 

Since retiring from anesthesia, Jeanne has been a nutrition educator at local middle and high schools in the San Francisco Bay Area. She teaches her students the importance of eating food closest to the source, making good food choices and eating in a balanced and moderate way.  Jeanne started SOUL (seasonal, organic, unprocessed, local) Food Salon in 2014. SOUL Food Salon’s mission is to educate and empower people to be healthier. She holds small gatherings (salons) at which experts in the health and wellness community share their knowledge on how to lead a healthier life.

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