Antioxidants present in our diet along with endogenous antioxidants that is those present in our body play an important role in the neutralization of oxidative stress. When the diet lacks nutrient antioxidants, it becomes one of the reasons why people get afflicted by chronic and degenerative diseases. Each nutrient has its own unique structure and antioxidant function. Some vitamins also exhibit antioxidant property.

Vitamin E

Vitamin E is a fat-soluble vitamin and is a very potent antioxidant. Vitamin E is actually a group of eight stereoisomers which have similar activity. The eight or so vitamin E molecules can be divided into two groups tocopherols and tocotrienols. Vitamin E found in the body is mostly in the form of α-tocopherol and it is in this form it exhibits the powerful activity of antioxidant (1).

Antioxidant property of vitamin E

The fat-soluble, α-tocopherol protects cell membranes from the harmful effects of free radicals. Its antioxidant activity is displayed through protection against lipid peroxidation (2). The antioxidant activity of vitamin E seems to come from donating electrons to the free radicals and neutralising them (1).

Vitamin E is the main lipid-soluble constituent in the cell antioxidant defence system. The main source of vitamin E is diet. Oxidation has been linked to many diseases and vitamin E has been shown to counteract oxidation (3).

Vitamin E dietary sources (2)

• Vegetable oils
• Wheat germ oil
• Nuts

Vitamin C

Vitamin C also known as ascorbic acid, is a water-soluble vitamin and the health benefits of vitamin C are antioxidant, anti-atherogenic, anti-carcinogenic, immunomodulator activities. The protective effect of vitamin C has been shown in

• Reducing the incidence of stomach cancer
• Preventing lung and colorectal cancer (2).

Antioxidant property of vitamin C

Vitamin C and vitamin E work together to quench free radicals. Vitamin C also regenerates/reactivates the reduced form of vitamin E (2). Vitamin C acts as a co-antioxidant for α-tocopherol by converting α-tocopheroxyl radical to α-tocopherol (4).

Vitamin C is a dietary antioxidant and it reduces the negative effect of reactive species such as reactive oxygen and nitrogen species. These reactive molecules or free radicals may cause oxidative damage to molecules such as lipids, DNA and proteins. The damage may cause chronic diseases including cardiovascular disease, stroke, cancer and neurodegenerative diseases in the long run.

Vitamin C dietary sources

• Acid/citrus fruits
• Green vegetables
• Tomatoes

Beta-carotene

Carotenoids are structurally and functionally a very varied group of natural pigments. Beta-carotene is a fat-soluble carotenoid and is a provitamin that can be converted to active vitamin A.  Dietary carotenoids exhibit antioxidant activity and protect against cancer, cardiovascular or photosensitivity (skin) disorders (5).

Antioxidant property of beta-carotene

It is a potent antioxidant and is the best neutralizer of singlet oxygen a free radical (2). All the beta-carotene consumed is not converted to vitamin A and performs other functions in the body. Beta-carotene and other carotenoids such as lutein and lycopene function as antioxidants and are also called nutraceuticals (1).

Beta-carotene dietary sources

• Fruits
• Vegetables (carrots, green plants, squash, spinach)

Final word

Having a balanced diet that has plenty of fruits and vegetables will be a good source of these vitamins. Not only do vitamins have several nutritional roles to play in the body but also provide antioxidant value to help protect us from several diseases.

References

1. Wildman, R. (2009) The Nutritionist-Food, Nutrition, and Optimal Health. Routledge, Taylor and Francis Group. Second Edition. New York and London.

2. Pham-Huy, L. A., He, H. and Pham-Huy, C. (2008) Free radicals, antioxidants in disease and health, International journal of biomedical science: IJBS. Vol. 4(2). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614697/

3. Rizvi, S., Raza, S. T., Ahmed, F., Ahmad, A., Abbas, S. and Mahdi, F. (2014) The role of vitamin E in human health and some diseases, Sultan Qaboos University medical journal. Vol. 14(2).

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3997530/

4. Naidu, K.A. (2003) Vitamin C in human health and disease is still a mystery? An overview, Nutrition Journal. Vol. 2(7).

https://nutritionj.biomedcentral.com/articles/10.1186/1475-2891-2-7#Tab2

5. Fiedor, J. and Burda, K. (2014) Potential role of carotenoids as antioxidants in human health and disease, Nutrients. Vol. 6(2).https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3942711/