Why are Antioxidants considered Superfoods?

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It is a very common practice for food manufacturers to slap on the ‘rich in antioxidants’ label onto their products as a marketing tool. However, what does this phrase actually mean? What are antioxidants and what are their health benefits?

Antioxidants are substances which control the rate at which free radicals, reactive oxygen species (ROS), and reactive nitrogen species (RNS) are formed as a by-product within our body. A few well-known antioxidants include vitamin C, vitamin E and beta-carotene, which are found in high quantities in different fruits and vegetables (for example, beta-carotene is a antioxidant pigment which gives carrots their orange colour). These nutrients help prevent diseases such as stroke, heart disease, lung disease and cancer, which are leading causes of death globally.

Free radicals are unstable molecules with an unpaired electron and are usually highly chemically reactive. Reactive oxygen species are chemically reactive compounds containing oxygen, and reactive nitrogen species are chemically reactive compounds containing nitrogen. These three terms can be collectively described as oxidants, which are substances that actively steal an electron from other reactants. Examples of oxidants found in our body include hydroxyl (OH), superoxide (O2•–), nitric oxide (NO), nitrogen dioxide (NO2), hydrogen peroxide (H2O2) and hypochlorous acid (HOCl).  Free radicals and reactive oxygen/nitrogen species cause damage to cells by changing the chemical bonding properties of proteins, by gaining electrons through a process called oxidation. They can also cause damage to our DNA and alter its composition, or change the structure of a cell membrane, thus ameding what substances are allowed to exit or enter the cell. This cumulative damage that the free radicals and the ROS cause, is known as oxidative stress.

An example of a reaction that free radicals undergo is the formation of a harmful type of cholesterol called oxidised low density-lipoprotein (LDL). The free radical causes damage to normal LDL cholesterol by disrupting its chemical bonding and structure. The presence of oxidised LDL in the arteries promotes the build-up of lymphocytes (white blood cells) and other lymphatic cells, causing the clogging of the artery, therefore restricting the blood flow, eventually leading to cardiovascular diseases.

Free radicals and ROS/RNS have also been linked to aging which is known as the Free Radical Theory. The theory proposes that the cumulative damage that the oxidant molecules have done to the body is the root cause of aging. However, the evidence behind this theory is inconclusive.

Free radicals and ROS are formed in the body as a by-product when producing ATP (adenosine triphosphate) in our mitochondria. However, our metabolism isn’t the only cause of the formation of free radicals. Environmental factors also play an important role. For example, exposure to cigarette smoke, heavy sunlight, radiation, pesticides and solvents are also root causes of free radical and ROS/RNS accumulation in the body.  Moreover, numerous studies have shown that a sudden onset of intense physical activity, from otherwise infrequent exercisers, causes free radicals to form at a faster rate. Free radicals also result in a chain reaction, meaning that one free radical can be used to form another free radical during the propagation stage of its reaction.

Antioxidants have the ability to donate a second electron to these free radicals, and to ROS/RNS, in order to reduce their reactivity. This creates a pause in the chain reaction of the free radical formation process, which prevents them from causing harm to our body.

So, if antioxidants have such great properties, should I be taking antioxidant supplements to reduce the number of free radicals in my body? Research has shown that there is no need to be taking excess antioxidants from supplements. Taking large doses of antioxidants have very little effect on our bodies and some antioxidants in excess can possibly cause harm to the body. Meta studies have shown that excess of antioxidants can lead to the development of certain types of cancer. Also, excess of vitamin A, often results in birth defects when taken by a pregnant woman. This observation is known as the ‘antioxidant paradox’.

Antioxidants are quite healthy and necessary when they come from natural foods. The human body does not create enough antioxidants in order to combat the free radical products from our metabolism mechanism and our environment, however, a balanced diet should provide all of our metabolic need for antioxidants. It is very important that we include foods like berries, beans and spinach within our diet in order to prevent the development of cardiovascular diseases, strokes, etc. However, ingesting additional antioxidant supplements is completely unnecessary, unless specifically recommended by a certified nutritional specialist, as it generally has little to no positive effect, and can potentially cause harm to the body.


References

  1. Harvard School of Public Health. Antioxidants. https://www.hsph.harvard.edu/nutritionsource/antioxidants/. (Accessed 07/05/20).
  2. Pham-Huy LA, He H, Pham-Huy C (2018). Free Radicals, Antioxidants in Disease and Health. Int J Biomed Sci, 4(2): 89-96. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3614697/.
  3. Moll J (2020). The Causes and Effects of Oxidized LDL Cholesterol.  https://www.verywellhealth.com/what-is-oxidized-ldl-698079 (Accessed 07/05/20).
  4. Wickens AP (2001). Ageing and the Free Radical Theory. Respir Physiol, 128(3): 379-91. https://www.ncbi.nlm.nih.gov/pubmed/11718765.
  5. Szalay J (2016). What are Free Radicals? https://www.livescience.com/54901-free-radicals.html (Accessed 07/05/20).
  6. Van De Walle G (2018). Should You take Antioxidant Supplements? https://www.healthline.com/nutrition/antioxidant-supplements#bottom-line (Accessed 07/05/20).

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