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Oxidative Stress 101

Written by Helen Quach, BS (Biochemistry) | Reviewed by Selfhacked Science Team | Last updated:

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Oxidative stress can cause many different diseases- cancer, brain disorders, heart problems, and more. Read more below to learn about how you can protect your body against its negative effects.

What is Oxidative Stress?

Scientists widely use the term “oxidative stress”. It refers to a serious imbalance between the production of free radicals and antioxidant defense, leading to potential tissue damage [1].

‘Free radical species’ summarizes a variety of highly reactive molecules that can be divided into different categories. The most prominent members of such categories include superoxide (O2·−), hydroxyl radical (OH·), and peroxy radical (ROO) [1].

Under normal conditions, the rate and magnitude of oxidant formation are balanced by the rate of oxidant elimination. However, an imbalance between prooxidants and antioxidants results in oxidative stress [2].

Oxidative stress can cause either a positive response (cell proliferation) or a negative cell response (growth arrest or cell death) [3].

What Are Free Radicals?

Reactive oxygen species (ROS) are produced by all vascular cell types, including endothelial, smooth muscle, and connective tissue cells, and can be formed by numerous enzymes [4].

Oxidants are also generated by different types of radiation, with X-irradiation generating the hydroxyl radical [5, 3].

Irradiation with UV light generates radical formation [53].

Ultrasound and microwave radiation can also generate reactive oxygen species [5].

Metal-catalyzed reactions (e.g. iron) produce reactive oxidant species [3].

They are present as pollutants in the atmosphere [3].

ROS are produced by neutrophils and macrophages during inflammation [3].

They are also by-products of mitochondria-catalyzed electron transport reactions and other mechanisms [3].

Benefits of Free Radicals

It has become apparent that plants actively produce ROS as a way to control processes such as programmed cell death, stress responses, defense against microbes and cellular communication [6].

Free radical reactions are essential for defending against microbes. Neutrophils, macrophages and other cells of the immune system produce these radicals. However, if the body overproduces free radicals, they cause tissue injury and cell death [1].

ROS within cells act as communication molecules and can induce cell death, which has anti-cancer benefits [3].

O2 and H2O2 function as cellular messengers that send signals to other parts of the cell or other cells. These may play an important role in cardiovascular disease [4].

ROS at low concentrations can be beneficial, for example, by triggering cell growth and reproduction and enhance the survival in a wide variety of cell types [3].

Other roles include regulation of the cellular calcium concentration, regulation of protein phosphorylation, and activation of certain transcription factors [3].

Bad Aspects of Free Radicals:

As many as 200 human diseases have been associated with increased levels of oxidative stress [7].

Reactive oxygen species (ROS) influence many physiological processes including the immune system and cellular communication and their increased production through oxidative stress plays a role in many diseases [4].

These diseases include:

  • Cardiovascular diseases: Vascular diseases [8], High cholesterol [8, 4], Stroke [4], Heart failure [4], Hypertension [84]
  • Cancer [8]
  • Parkinson’s disease [8]
  • Alzheimer’s disease [8]
  • Diabetes [4]
  • Kidney disease [4]

1) Free Radicals Damage Cells

At high concentrations, ROS can damage cell structures, including cellular fats (lipids, membranes), proteins and nucleic acids [3].

Oxidative damage accumulates during the life cycle, and it plays a key role in the development of age-related diseases such as cancer, arthritis, brain disorders and other conditions [3].

2) Oxidative Damage Helps Cause Diabetes

Both types of diabetics display increased levels of free radicals; for this reason, the onset of diabetes is closely associated with oxidative stress [1].

Damaged protein is a contributing factor to the mechanism by which oxidative stress accelerates diabetes complications [1].

It appears that oxidative stress byproducts contribute to insulin resistance, the basis of diabetes [1].

Also, recent research has demonstrated a direct link between the imbalance of oxidative stress and antioxidants leading to impaired glucose uptake [1].

3) Oxidative Damage Causes COPD

Oxidative stress damages and impairs the functioning of several kinds of proteins, harming the lungs in ways that can induce COPD, a chronic lung disease [9].

The harmful effects include inactivation of cells, excessive secretion of mucus, membrane damage, and cell death [9].

It can cause a negative cycle in COPD patients, because oxidative stress causes inflammation, and inflammation, in turn, causes more oxidative stress [10].

This cycle occurs because oxidation causes various protein dysfunctions, and that hinders the operation of functions that restore a healthy oxidant/antioxidant balance [10].

Free Radicals and Cancer

DNA mutation is a critical step in cancer formation and elevated levels of DNA damage caused by free radicals (as measured by 8-OH-G) are found in various tumors, strongly implicating such damage in causing cancer. It appears that DNA damage is predominantly linked with the initiation of cancer [3].

While a high level of oxidative stress is toxic to the cell and causes cell death, a low level of oxidative stress, on the other hand, can, in fact, stimulate the cell division in the promotion stage and thus stimulate the promotion of tumor growth [3].

Hence if you already have cancer, taking too many antioxidants might not be beneficial, because it can theoretically cause tumor growth (if you have a tumor).

What are Antioxidants?

Living organisms have evolved a number of antioxidant defenses to maintain their survival against oxidative stress [4].

In order to avoid free radical overproduction from oxidative stress, antioxidants are present in tissues to neutralize these free radicals [1].

Common antioxidants include vitamins A, C, and E, glutathione, and the enzymes superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase [11].

Other antioxidants include – lipoic acid, mixed carotenoids, coenzyme Q10, several bioflavonoids, antioxidant minerals (copper, zinc, manganese, and selenium), and the cofactors (folic acid, vitamins B1, B2, B6, B12) [11].

They work in combination with each other and against different types of free radicals [11].

What About Antioxidant Supplements?

Antioxidant supplements are not associated with a lower risk of dying [12, 13].

Beta-carotene, vitamin E, and higher doses of vitamin A may actually be associated with a higher risk of dying [12, 13].

Vitamin C (ascorbic acid) is a very important antioxidant that works in liquidy environments of the body, such as are present in the lungs and in the lens of the eye [3].

While intake of high doses of Vitamin C (up to 2,000 mg/day) has not been consistently reported to result in side effects, the benefit of a high intake of Vitamin C has never been established [3].

The optimal source of antioxidants seems to come from our diet, not from antioxidant supplements, especially in well-nourished populations [14].

Want More Targeted Ways to Combat Inflammation?

If you’re interested in natural and more targeted ways of lowering your inflammation, we at SelfHacked recommend checking out this inflammation wellness report. It gives genetic-based diet, lifestyle and supplement tips that can help reduce inflammation levels. The recommendations are personalized based on your genes.

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About the Author

Helen Quach

BS (Biochemistry)

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