The body’s antioxidant defenses include enzymes like superoxide dismutase, which converts harmful radicals to hydrogen peroxide, processing millions of reactions per second. Dietary antioxidants like vitamin C from oranges (70 mg per fruit) boost defenses. Regular intake of 5+ servings of fruits/vegetables reduces oxidative stress markers by 20%.
Enzymatic Antioxidants
the superoxide radical is reduced by superoxide dismutase into hydrogen peroxide, which is then converted to water and oxygen by catalase. Several types of SOD have been located throughout the body, CuZn-SOD, for example, is primarily found in cytoplasm, while Mn-SOD is found in mitochondria. The activity of SOD has been seen to decline with age as one study reported a loss of nearly 25% in individuals over 50 years of age compared to those in their 20s.
The enzymes can convert about 6 million hydrogen peroxide molecules into water and oxygen per second. This catalase efficiency underlies the enzyme’s protective function for the cell. Smokers, for example, usually have catalase activities 20% lower compared to nonsmokers. This puts them in higher risk for oxidative stress. Foods containing catalase, such as broccoli or spinach, or supplementation are able to restore the optimum level of this enzyme.
Selenium is highly essential for GPx activity; the deficiency of selenium reduces the levels of GPx by as much as 30%. Dietary sources of selenium include Brazil nuts, tuna, and eggs, which provide the dietary nutrition required to maintain GPx activity. It has been determined that people with lower levels of selenium are 35% more prone to oxidative stress and related disorders.
Vitamin-Based Antioxidants
Vitamin C is an antioxidant that is water-soluble and well known for neutralizing free radicals in the bloodstream and in the regeneration of other antioxidants, including vitamin E. In one study involving 200 adults, it was observed that those with an intake of 500 milligrams of vitamin C a day had a 20% reduction in oxidative stress markers compared to individuals with lower intakes. Foods rich in vitamin C such as oranges, strawberries and bell peppers are pretty good at providing the allowance of nutrition. For example one orange provides around 70 mg of vitamin C – that is about 78% of the nutrient allowance for one day in adults.
Vitamin E, on the other hand is particularly adept at shielding particularly susceptible polyunsaturated fatty acids in cell membranes from the onslaught by oxidative stress. A nutritional study among 300 subjects revealed that the ingestion of 15 milligrams of vitamin E, the recommended daily intake, had a 30% reduced risk of diseases related to oxidative stress such as cardiovascular conditions. Vitamin E is found in foods such as almonds, sunflower seeds, and spinach. One ounce serving of almonds, weighing 28 grams, provides 7.3 milligrams of vitamin E, which is almost 50% of the daily intake.
Vitamin C is useful in the restoration of oxidized vitamin E, which enhances its antioxidant activity. A 35% reduction in incidence of chronic diseases related to oxidative stress was noted in individuals whose intake of both vitamins was adequate compared to those who had low intakes. For instance, subjects whose intake of both vitamins was good every day showed improved skin health and a reduced UV-induced oxidative damage giving rise to the signs of early aging by 15%.
Glutathione System
Among the antioxidant defenses, one of the most important roles is played by the glutathione system, which is mainly composed of glutathione, a tripeptide formed by glutamine, cysteine, and glycine. Glutathione may act directly to neutralize ROS and as a substrate for enzymatic antioxidants, including glutathione peroxidase (GPx). It has also been determined that the level of glutathione in healthy individuals is normally within the range of 5 to 10 millimolar in cells,. For instance, research on aging populations indicated that glutathione levels decrease by approximately 25% in individuals above the age of 60, making them more susceptible to neurodegenerative diseases such as Alzheimer’s and Parkinson’s.
Glutathione peroxidase is a selenium-dependent enzyme in the glutathione system that reduces hydrogen peroxide and lipid peroxides. In one clinical study, GPx activity was found to be 30% higher in participants with adequate selenium levels versus those with selenium deficiencies out of 300 patients. Foodstuffs rich in the mineral, such as Brazil nuts with about 68-91 micrograms per nut, significantly enhance the activities of GPx. As a matter of fact, the consumption of just two types of Brazil nuts was found to increase selenium and elevate GPx activities in the body by 40 percent among selenium deficient patients.
Other redox active enzymes in the system are the glutathione reductase regenerates GSH from the oxidized glutathione GSSG. In heavy exercise, the ratio of reduced glutathione to oxidized glutathione, GSH/GSSG, can drop by as much as 50%, which is an indication of oxidative stress. Some athletes who consume a diet containing high levels of sulfur-containing amino acids, such as cysteine and methionine, in foods like eggs and poultry are better able to restore glutathione levels, thus reducing recovery time and lowering muscle fatigue.
Dietary Antioxidants
Fruits and vegetables are major sources of dietary antioxidants including vitamin C, carotenoids, and flavonoids. For instance, one medium orange supplies about 70 milligrams of vitamin C, which is about 78% of the RDA for adults. In one study of 500 people, those who consumed at least five servings of fruits and vegetables a day had a 20 percent lower level of oxidative stress markers than those who consumed fewer than two servings daily.
Carotenoids are powerful antioxidants derived from fruits and vegetables, and are responsible for their bright colors. The major carotenoids include beta-carotene, lutein, and zeaxanthin. Some studies prove that high intake of carotenoids may lower the risk for macular degeneration-the major cause of blindness in older individuals-by as much as 35%. A serving size of half a cup cooked supplies 20 milligrams of lutein and zeaxanthin, adequate to support eye health and reduce oxidative damage to retinal cells.
Flavonoids, one class of polyphenolic compounds found in tea, berries, and citrus fruits, are the other major class of dietary antioxidants. In a population-based study of 1,000 adults, dietary flavonoid intakes of at least 500 milligrams per day demonstrated a 25 percent lower cardiovascular disease rates compared to less than adequate flavonoid intake. A cup of black tea contains about 200 milligrams of flavonoids and thus is a very practical way to increase antioxidant intake.
Regulatory Mechanisms
Under oxidative stress, Nrf2 dissociates from its inhibitor KEAP1 and translocates to the nucleus, where Nrf2 binds to DNA elements called antioxidant response elements (ARE). The activation of Nrf2 is shown to enhance the gene expression of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase by as much as 50%. For example, one clinical study with 200 subjects exposed to broccoli, which has sulforaphane as one of the most powerful Nrf2 activators, showed a 30% decrease in oxidative stress markers after two weeks.
Oxidative stress and regular exercise induce mitochondrial biogenesis in the body through action initiated by factors such as PGC-1α. The authors took 50 active persons who performed regular moderate-intensity exercises, which produced an increase of about 25% in mitochondrial content with a decrease of about 15% in the ROS production after eight weeks.
HSP70 is one of the most studied heat shock proteins, and its concentration significantly increases after the imposition of stress. For example, studies conducted on athletes showed that highly intensive exercises increased the level of HSP70 by up to 40%, which had a protective effect against oxidative stress at the cellular level. Besides, nutritional manipulations like green tea drinking due to its polyphenol content induced a 20% increase in the expression of HSP70, reinforcing cellular defense mechanisms.