Antioxidants and the Free Radical Damage
We examine the actions of free radical damage in our bodies, and how antioxidants stop them.
Undergoing within our bodies without our awareness are biological processes called free radical damage that are harmful to us. The environment, sun exposure, foods we eat, and even the oxygen we breathe contribute to the free radical damage that our body endures everyday. These free radicals, when left unattended, damage our bodies from within our cells themselves. They are believed to be the cause of early aging and major diseases like cancer.
Free radicals damage the basic unit of our bodies - the cell - by breaching its cell membrane. Our cells are protected with an outer membrane made up of lipids (fats). These membranes are very vulnerable and readily oxidized when exposed to free radicals. Unstable compounds called reactive oxygen species (ROS), atoms that have unpaired electrons, damage cells in a self-propagating chain reaction which is similar to a series of dominoes falling. These type of damage is grouped into: superoxide anion (2 oxygen with unpaired electron), peroxide (2 oxygen with 2 unpaired electrons), and hydroxyl radical (oxygen bonded to hydrogen with one unpaired electron). They usually start in small amounts, attacking the polyunsaturated fatty acids of the fatty acid membrane. This is very dangerous for the viability of cells, which damages our DNA material (mutation), accelerates the aging process, and causes cancer and other degenerative diseases like atherosclerosis, IBD, ROP, BPD, asthma, Parkinson's disease, kidney damage, preeclampsia, and others.
Besides cell membranes, another group of lipids that is easily oxidized by free radicals is cholesterol. Cholesterol is an important component of our body, as it is a precursor to steroidal hormones, bile acids, and our cell membranes as well. Cholesterol in our blood is carried mostly by low-density lipoprotein (LDL), or the "bad" cholesterol. Too much LDL is bad for our health, as it is the cause of various cardiovascular disease. When the LDL gets oxidized by free radicals, they become toxic and damages the tissue cells of our blood vessels. The end result is a progressive thickening of arteries from the oxidation byproducts of the LDL which makes up the plaque that clogs our blood vessels.
Antioxidans act on these free radicals by getting themselves oxidized instead of our cells. This stabilizes the free radical and is then safely removed from the body. The water soluble or hydrophilic antioxidants like Vitamins A and C are more active in blood plasma, while the water insoluble or hydrophobic antioxidants like Vitamin E are active in the cell membrane. Our bodies also produce its own antioxidants. Selenium, manganese and zinc are trace elements that are important components of several antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase that our bodies produce. These enzymes work as both primary and secondary antioxidants and help repair oxidized DNA and target cells whose membranes have been damaged.
Fruits and vegetables are a great source of free radical-scavenging antioxidants. The phenolic group of antioxidants present in these foods can quench and terminate free radicals without transforming into free radicals themselves. They also act to chelate free radical producing metal ions. Protocatechuic, caffeic, coumaric and chlorogenic acids are phenolic acids found in abundance in fruits and vegetables. Ferulic acid is a phenolic acid commonly found in grains, especially in grain bran. Polyphenolics are a group of flavonoids, which are divided into anthocyanins, isoflavones, flavones, flavonols, flavanols, and flavanones. Anthocyanins are present in high levels in berries, and isoflavones are abundant in beans. The flavonol quercetin is largely present in apples, while catechin, a flavanol, is found in teas and coffees. Grapefruits are rich in flavanones, such as naringenin. Tannins are a group of polymerized polyphenolics present in berries and red wines.
This article is just a first of the many series of articles we will be publishing about the very important topic of antioxidants. Stay tuned for future articles.
April 29, 2013
- Lipid peroxidation and tissue damage. Department of Pharmacology, University of Leeds, U.K.
- Hanaa Ali Hassan Mostafa Abd El-Aal. Lipid Peroxidation End-Products as a Key of Oxidative Stress: Effect of Antioxidant on Their Production and Transfer of Free Radicals.
- Important Antioxidant Phytochemicals in Agricultural Products. Wiley-Blackwell Publishing.