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'''Oxidative stress''' is a critical factor in the aging process and is believed to contribute significantly to the deterioration of physiological functions over time. This concept has been supported by extensive research and studies over the years.

== Reactive Oxygen Species (ROS) ==
Oxidative stress is characterized by an imbalance between the production of '''reactive oxygen species (ROS)''' and the body's ability to detoxify these reactive intermediates or to repair the resulting damage.{{pmid|28441057}} ROS are highly reactive molecules, including free radicals like superoxide radicals (O<sub>2</sub><sup>-</sup>), hydroxyl radicals (OH<sup>.</sup>), and non-radical species such as hydrogen peroxides (H<sub>2</sub>O<sub>2</sub>).{{pmid|23434764}}

Reactive oxygen species (ROS) are primarily produced by the mitochondria during normal metabolic processes, with the electron transport chain being a significant source.{{pmid|31733333}} The production of ROS is a complex process involving the reduction of oxygen molecules, leading to a cascade of other ROS.

Additionally, ROS are produced through various physiological and pathological processes, including cellular respiration and inflammatory responses.{{pmid|23063822}} Their generation and subsequent conversion involve enzymes like superoxide dismutase (SOD), catalase, and glutathione peroxidase, which play crucial roles in controlling oxidative stress.

==The Oxidative Stress Theory of Aging==
The oxidative stress theory of aging posits that the gradual accumulation of oxidative damage to biomolecules is a primary driver of the aging process. This damage increases with age and correlates with a decline in life expectancy in various organisms.{{doi|10.1016/S1566-2772(03)00007-0}} Oxidative damage affects multiple aspects of aging and is a key factor in many age-related diseases. Particularly, telomeres are highly susceptible to oxidative damage, which can lead to accelerated aging and increased risk of age-related diseases.{{pmid|10911951}}{{pmid|12114022}}{{pmid|26785477}}

==Controversy and Complexity in Oxidative Stress Research==
While there is substantial evidence linking oxidative damage to aging, the direct relationship between oxidative stress and aging is not conclusively established.{{pmid|12208343}} ROS have complex roles in the body, contributing to cellular homeostasis at physiological levels but causing damage when in excess.{{pmid|28441057}} This dual role is embodied in the concept of mitohormesis, where low levels of ROS can be beneficial.

==Impact of Oxidative Stress on Biomolecules==
Oxidative stress can lead to damage in various biomolecules:
*'''Lipids:''' Polyunsaturated fatty acids (PUFAs) are particularly vulnerable to lipid peroxidation, affecting membrane fluidity and leading to cell apoptosis.{{pmid|21861450}}{{pmid|28192230}}
*'''Proteins:''' Oxidation of proteins can alter their structure and function, affecting enzyme activity and signal transduction.{{pmid|9252331}}{{pmid|27026395}}{{pmid|17090414}}{{pmid|2244532}}{{pmid|24632383}}
*'''Nucleic Acids:''' ROS, especially hydroxyl radicals, can cause oxidative damage to DNA, leading to mutations, strand breaks, and DNA-protein cross-linking, contributing to genome instability and cell death.{{pmid|31733333}}{{pmid|8379000}}{{pmid|23417673}}{{pmid|10720713}}{{pmid|12796402}}{{pmid|2545260}}

== Antioxidants ==

'''Antioxidants''' are compounds that can prevent or slow down the oxidation of other molecules. Oxidation is a chemical reaction that can produce free radicals, leading to chain reactions that may damage cells. Antioxidants terminate these chain reactions by removing free radical intermediates and inhibiting other oxidation reactions. They do this by being oxidized themselves, making them crucial in the body's defense against oxidative stress.{{pmid|28441057}}

There are several types of antioxidants, each playing a distinct role in combating oxidative stress:

* '''Enzymatic Antioxidants:''' These include enzymes such as superoxide dismutase (SOD), catalase, and glutathione peroxidase, which directly neutralize ROS.
* '''Non-enzymatic Antioxidants:''' This group includes Vitamin C, Vitamin E, and glutathione. These small molecule antioxidants scavenge free radicals and contribute to the repair and regeneration of oxidized antioxidants.
* '''Metal-Binding Proteins:''' Proteins such as ferritin and ceruloplasmin that sequester free iron and copper ions, which can catalyze the production of free radicals, thus reducing oxidative stress.

=== Dietary Sources of Antioxidants ===
Diet is a significant source of antioxidants. Foods high in antioxidants include:

* '''Fruits and Vegetables:''' Berries, citrus fruits, and leafy greens are high in vitamins C and E, as well as various phytochemicals.
* '''Nuts and Seeds:''' These are sources of vitamin E and selenium, another important antioxidant.
* '''Whole Grains:''' Whole grains contain antioxidants like vitamin E and phytochemicals.
* '''Tea and Coffee:''' Rich in flavonoids, these beverages contribute significantly to the total antioxidant intake.

==Antioxidant Supplements ==
Antioxidant supplements have gained popularity as potential aids in combating oxidative stress and its related aging processes. These supplements are concentrated forms of antioxidants that can be taken in addition to a regular diet.

Here's a list of some widely used antioxidant supplements:

* '''Vitamin C (Ascorbic Acid)''': A water-soluble vitamin known for its role in boosting the immune system and scavenging free radicals.
* '''Vitamin E (Tocopherol)''': A fat-soluble vitamin that protects cell membranes from oxidative damage, especially in lipid-rich areas of the body.
* '''Beta-Carotene''': A precursor to vitamin A and a powerful antioxidant, particularly effective against singlet oxygen.
* '''Selenium''': A trace mineral that is a component of antioxidant enzymes like glutathione peroxidase.
* '''Zinc''': Essential for the functioning of several antioxidant enzymes and immune function.
* '''[[Coenzyme Q10 (CoQ10)]]''': An important molecule in energy production and also acts as an antioxidant in cell membranes and lipoproteins.
* '''Flavonoids''': A diverse group of phytonutrients found in many fruits and vegetables, known for their antioxidant properties.
* '''Lycopene''': A carotenoid found in tomatoes, watermelon, and other red fruits and vegetables, known for its antioxidant capacity.
* '''[[Resveratrol]]''': Found in the skin of red grapes, berries, and peanuts, resveratrol is studied for its antioxidant and anti-aging properties.
* '''Curcumin''': The active ingredient in turmeric, curcumin possesses strong antioxidant and anti-inflammatory properties.
* '''Alpha-Lipoic Acid''': A compound that works with mitochondria and the body's natural antioxidant defenses.
* '''Green Tea Extract''': Rich in catechins, green tea extract is renowned for its antioxidant properties.

== Limitations and Considerations ==
While antioxidants are beneficial, their supplementation is not without limitations. Excessive intake of some antioxidants can be harmful, and the balance between antioxidants and ROS is crucial. The concept of antioxidant supplementation is complex, and more research is needed to fully understand its implications for health and aging.

A 2007 meta-analysis finds that in studies with a low risk of bias (randomization, blinding, follow-up), some popular antioxidant supplements (vitamin A, beta carotene, and vitamin E) may increase mortality risk (although studies more prone to bias reported the reverse).{{pmid|17327526}}

== Conclusion ==
In summary, oxidative stress is a multifaceted factor in aging, with a significant impact on various biomolecules, leading to physiological decline and increased risk of age-related diseases. Understanding and mitigating oxidative stress remains a key area in longevity research.

== Further Reading ==

* {{pmid text|29731617}}
* {{pmid text|35159361}}

== See Also ==

* {{SeeWikipedia|Oxidative stress|}}

== References ==
<references />
[[Category:Aging]]