Antioxidants are naturally occurring plant substances that protect the body from damage caused by harmful molecules called free radicals. Antioxidants help prevent oxidation, which can cause damage to cells and may contribute to aging. They may improve immune function and perhaps lower the risk for infection, cardiovascular disease, and cancer. Antioxidants exist as vitamins, minerals and other compounds in foods. A diet containing plenty of fruits and vegetables, whole grains and nuts can supply all the antioxidants your body needs. Diets rich in antioxidants can be very beneficial.
A few of the better known antioxidants include carotenoids (a form of vitamin A) — the substance that gives fruits and vegetables their deep rich colors. Apricots, broccoli, pumpkin, cantaloupes, spinach and sweet potatoes are good choices. Foods containing vitamins C and E are also good sources of antioxidants, as well as selenium and zinc.
Commonly Known Antioxidants and their food sources:
• Carotenoids (a form of vitamin A) the substance that gives fruits and vegetables their deep rich colors. May be effective allies against prostate cancer Apricots, peaches, broccoli, pumpkin, cantaloupes, carrots, spinach and sweet potatoes
• Vitamin C enhances the immune response and protects against infection. Citrus fruits like oranges and lime etc., green peppers, broccoli, green leafy vegetables, strawberries and tomatoes
• Vitamin E may help prevent the oxidation of LDL or “bad” cholesterol which contributes to plaque buildup in the arteries. Nuts and seeds, whole grains, green leafy vegetables, vegetable oil and liver oil
• Selenium Fish and shellfish, red meat, grains, eggs, chicken and garlic
Oxidative stress is a condition caused by an imbalance between the free radicals and antioxidant defence system of the body. In health, free radicals and antioxidants remain in balance state, but in conditions of oxidative stress, there is a large number of reactive oxygen species and reactive nitrogen species than the antioxidant. Some atoms are unstable and highly reactive due to the presence of unpaired electrons in valence orbitals. They attain stability by acquiring electrons from nearby molecules in the body, causing a cascade of reactions resulting in cellular damage and diseases.
Oxidative stress has been reported to play a significant role in the pathogenesis of diseases like Diabetes mellitus, renal failure, cardiovascular diseases, cancer, polycystic ovary syndrome, neurodegenerative diseases. Antioxidants neutralise excess free radicals. Antioxidants are produced in the body (endogenous) or acquired from the diet (exogenous). Many studies have reported a decrease in endogenous antioxidants in many disease conditions. Therefore, intake of exogenous antioxidants in the diet becomes vital to improve the dangerous effect of reduced antioxidants and increased free radicals in disease conditions.
Vitamin A and oxidative stress
Vitamin A is also called retinoic acid, and it possesses the ability to inhibit viral hepatitis. Even though vitamin A is not a popular antioxidant, few studies reported a likely antioxidant role in an indirect way. All-trans retinoic acid was reported to play a key role in the inhibition of hepatic stellate cells (an effector of hepatocellular carcinoma) activation via suppressing thioredoxin-interacting protein and reduces oxidative stress levels. Also, retinoic acid, which is a metabolite of vitamin A, was reported to up regulate expression of anti-oxidant related genes in in-vitro mature buffalo oocytes.
Furthermore, all-trans retinoic acid-induced superoxide dismutase and glutathione transferase activities, while it decreased malondialdehyde and reactive oxygen species in both healthy and varicocele sperm, which suggests that retinol enhances antioxidant enzyme activity. Therefore, there is growing evidence suggesting that vitamin A could play a role in protecting the body against oxidative stress damage.
Vitamin D and oxidative stress
Vitamin D exists in three forms, which are 7‐dehydrocholesterol, ergocalciferol, and cholecalciferol. All these three forms have been reported to inhibit iron-dependent lipid peroxidation, and the antioxidant ability of vitamin D was reported to be comparable to the anticancer drug Tamoxifen. Numerous evidence is supporting the antioxidant activity of Vitamin D3 (cholecalciferol) in oxidative stress diabetes. Some experimental studies
reported that vitamin D3 administration in diabetic mice helps to diminish the ROS formation by the suppression of the gene expression of NADPH oxidase.
Furthermore, Vitamin D supplementation has been suggested to provide significant protection against oxidative stress-mediated vascular complications in diabetes. Also, a study proposed that vitamin D is an antioxidant because of an increase in hepatic GSH amounts in rats that have gotten cholecalciferol. Vitamin D supplementation for nine weeks among pregnant women has beneficial effects on biomarkers of oxidative stress. It
caused a significant increase in total antioxidant capacity and glutathione activity, among other metabolic enzymes.
Vitamin E and oxidative stress
Vitamin E discovered in 1922, together with its physiological functions, and its anti-oxidative effects, have been studied for nearly a century now. Vitamin E is fat-soluble compounds divided into tocopherols and tocotrienols each occurring in the alpha, beta, gamma, and delta forms. Alpha-Tocopherol received the most attention among the vitamin E with antioxidant potentials, but some studies suggested that tocotrienols may
have different health promoting capacities.
An increased concentration of alpha-tocopherol in the liver was found to exert a protective effect against oxidative damage in exercise-induced oxidative stress. Also, Alpha-Tocopherol protects cell membranes from lipid peroxidation by superoxide radical anion and lipid peroxyl free radical scavenging. Also, alpha-tocopherol was reported to reduce
oxidative stress in workers exposed to lead, and the administration of alphatocopherol reversed adverse health effects of lead exposure, which induced oxidative stress.
Vitamin K and oxidative stress
Vitamin K occurs in three forms, which are K1 (Phylloquinone), K2 (Menaquinone) and K3 (Menadione). Leafy plants produce Phylloquinone (vitamin K1). In contrast, menaquinone is a product of bacterial from the gut or conversion of phylloquinone derived from the diet. Hence, menaquinone is the most abundant form of vitamin K in animal tissues. One of the mechanisms for ROS production in the body is through activation of 12lipoxygenase an enzyme involved in arachidonic acid metabolism.
Vitamin K has been reported to block the activation of 12-lipoxygenase in arachidonic acid-induced oxidative injury to developing oligodendrocytes, a report from the same research group showed that phylloquinone (vitamin K1) and menaquinone 4 (MK4; a vitamin K) protect developing oligodendrocytes and immature neurons against glutathione depletion induced oxidative injury and generation of ROS. Also, vitamin K hydroquinone (KH2) was a potent biological antioxidant, there is a shortage of information on the regenerative antioxidative enzymatic mechanisms for this required trace nutrient which could be an area of research interest.
Vitamin C and oxidative stress
Vitamin C serves as an important nutrient for the body. Ascorbate is a powerful antioxidant with the ability to mop up free radicals within, and outside the cell which is by acting directly on peroxyl radicals or indirectly by boosting the antioxidant properties of vitamin E, this helps to control lipid peroxidation of cellular membranes and nuclear
materials of the cell.Ascorbate, due to its well-known antioxidant property, ameliorates DNA damage by decreasing reactive oxygen species or protects proteins involved in DNA repair. Ascorbate also prevents the formation of nitrosamine, which produces reactive nitrogen species. Vitamin C, in combination with L-carnitine, was reported to improve cisplatin-induced nephrotoxicity due to their antioxidant and anti-inflammatory property.
B complex vitamins and oxidative stress
It is involved in energy production from carbohydrates and fats. Vitamin B1 acts
as a co-enzyme precursor of some key enzymes of carbohydrate metabolism. It also helps in the structural development of brain cells, and it is involved in the detoxification of alcohol
It is involved in energy metabolism. Vitamin B2 recycles glutathione which is the most crucial antioxidant which protects against free radicals in the body. It also promotes iron metabolism and its deficiency increases the risk of anaemia as iron is an essential element for red blood cell production.
Vitamin B3: Niacin Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP)
They are primarily involved in the production of energy from dietary proteins, carbohydrates, and fats. NAD, NADP, and niacin-containing enzymes are scavengers of free radicals and protect tissues from oxidative damage.
Pantothenic acid incorporated into Coenzyme A (CoA) has a central position for energy metabolism.
Vitamin B6: Pyridoxine
Vitamin B6 is involved in red blood cell production, carbohydrate metabolism, liver detoxification, brain and nervous system health. It is also involved in the production of neurotransmitters in the brain and nervous system. Vitamin B6 helps in liver detoxification and its deficiency cause the liver dysfunctioning.
Vitamin B6 deficiency was found to be linked with attention deficit disorder.
Vitamin B9: Folate
Vitamin B9 is essential for brain health and provides support for the cardiovascular and nervous system in human. It is also vital for the production of red blood cells.
Vitamin B12: Cobalamin
It plays an essential role in energy metabolism Vitamin B12 needed for erythrocyte maturation during the production of red blood cells, and it plays a role in the maintenance of cardiovascular health of human by preventing an increase in the level of homocysteine. Vitamin B12 also maintains bone health as the incidence of osteoporosis is increased with
deficiency of this vitamin
It is a member of B-complex vitamins, and most importantly, Biotin plays a crucial role in sugar and fat metabolism. Biotin is needed for fat deposition in the skin as biotin deficiency causes skin rashes.
Vitamin C is well known for its antioxidant properties protecting cellular structures from harmful effects of free radicals. It also plays a role in iron absorption by transforming iron into a form which can be easily absorbed into intestines. Also, Vitamin C is needed for collagen production, which is a structural component of the human body. The synthesis of certain neurotransmitters is also dependent on vitamin C, especially neurotransmitters involved in signalling of feelings, thoughts, and commands throughout the brain and nervous system. Vitamin C is also prerequisite for the synthesis of serotonin, a hormone needed for the proper functioning of the endocrine system, nervous system, digestive system and immune system.