Free Radicals: Cause And Concern

POLLUTION, STRESS AND FAULTY FOOD HABITS > FREE RADICALS > OXIDATIVE STRESS > INCREASED CELL DAMAGE.

Mounting scientific evidence may support the important role of free radicals in the development of some diseases. 

Free radicals are molecules or atoms that have at least one unpaired electron which usually increases the chemical reactivity of the molecule. 

Environmental radiation/stress/many other pollutants and physiological processes in the body cause free radicals to form. 

Free radicals can react with other molecules to cause cell damage or DNA mutation. 

Molecules called antioxidants protect against free radical damage. 

When antioxidants are ineffective, enzymes produced by the body work to repair free radical damage. 

Higher levels of free radicals tend to cause increased cellular damage. This effect is called oxidative stress. Oxidative stress may contribute to cardiovascular disease and cancer. 

Chemical compounds found in some foods may decrease the accumulated effects of oxidative stress, thus helping to prevent disease. 

Free Radicals: Atoms contain a nucleus, and electrons move around the nucleus, usually in pairs. A free radical is any atom or molecule that contains one or more unpaired electrons.
           The unpaired electrons alter the chemical reactivity of an atom or molecule, usually making it more reactive than the corresponding non-radical. However, the actual chemical reactivity of radicals varies enormously. 
           The hydrogen radical ([H.sup.*], the same as a hydrogen atom), which contains 1 proton and 1 electron (therefore unpaired), is the simplest free radical. Free-radical chain reactions are often initiated by removal of [H.sup.*] from other molecules. A superscripted dot is used to denote free radicals. 

Free radicals and chain reaction:  Most molecules in the body are not radicals. Hence any reactive free radical generated is likely to react with a non-radical. When a free radical reacts with a non-radical, a free-radical chain reaction results and new radicals are formed. Figure 1 shows two important reactions of this type. Attack of reactive radicals on membranes or lipoproteins starts lipid peroxidation, which is particularly implicated in the development of atherosclerosis. If hydroxyl radicals are generated close to DNA, they can attack the purine and pyrimidine bases and cause mutations. For example, guanine is converted into 8-hydroxyguanine and other products.

Free radicals and premature aging: Air pollutants rob skin cells of oxygen and cause free radical production in the skin. This, in combination with UV radiation decreases the production of collagen and elastin, causing the skin to thin and lose elasticity, leading to sagging skin, fine lines, and wrinkles.

Free radicals and diseases: Free radicals are capable of damage biomolecules, provoke immune response, activate oncogens, cause atherogenesis and enhance ageing process. However, in healthy conditions nature has endowed human body with enormous antioxidant potential. Subtle balance exists between free radical generation and antioxidant defence system to cope with oxidative stress by various enzymes and vitamins at cellular level which prevent the occurrence of disease. However, factors tilting the balance in favour of excess free radicals generation lead to widespread oxidative tissue damage and diseases. Therefore, trouble starts when there is an excess of free radicals and the defence mechanism lags behind. Overwhelming production of free radicals in response to exposure to toxic chemicals and ageing may necessitate judicious antioxidant supplement to help alleviate free radical mediated damage.

tropospheric mean concentrations of (a) O₃, (b) OH, (c) H₂O₂ and (d) the surface Δ¹⁷O(SO₄^2-).  The measurement locations are shown in (a).

Free radicals with pollutants: Highly reactive molecules called free radicals can cause tissue damage by reacting with polyunsaturated fatty acids in cellular membranes, nucleotides in DNA, and critical sulfhydryl bonds in proteins. Free radicals can originate endogenously from normal metabolic reactions or exogenously as components of tobacco smoke and air pollutants and indirectly through the metabolism of certain solvents, drugs, and pesticides as well as through exposure to radiation. There is some evidence that free radical damage contributes to the etiology of many chronic health problems such as emphysema, cardiovascular and inflammatory diseases, cataracts, and cancer. Defenses against free radical damage include tocopherol (vitamin E), ascorbic acid (vitamin C), beta-carotene, glutathione, uric acid, bilirubin, and several metalloenzymes including glutathione peroxidase (selenium), catalase (iron), and superoxide dismutase (copper, zinc, manganese) and proteins such as ceruloplasmin (copper). The extent of tissue damage is the result of the balance between the free radicals generated and the antioxidant protective defense system. Several dietary micronutrients contribute greatly to the protective system. Based on the growing interest in free radical biology and the lack of effective therapies for many of the chronic diseases, the usefulness of essential, safe nutrients in protecting against the adverse effects of oxidative injury warrants further study.

Free radicals with oily fried foods (through lipid oxidation): Modern industrial environments, lifestyles and poor nutrition contribute heavily to Free Radical production.  When the body is low on antioxidants Free Radicals increase.  Additionally, unprotected exposure to the sun produces Free Radicals in the skin, mental and emotional stress are key causes of Free Radicals, as is smoking, the taking of drugs of any kind (including alcohol), cooked oils or fats, exposure to petrochemicals, heavy metals, and even excess adrenaline or insulin all take part in Free Radical production in our bodies.

WHAT CAN STOP A FREE RADICAL? (ANTIOXIDANTS): A free radical is stopped when the electron difference (gaining or losing an electron) is corrected.  Molecules that can correct the electron difference are called Antioxidants.  The process of damage by Free Radicals is called oxidation (think rust on metal or the browning of a cut apple), and the process that prevents it is anti-oxidation, and the molecules which do the prevention are called Antioxidants. Antioxidants are found in dark colored vegetables and fruit and in dietary supplements. The life of a free radical has three stages: the initiation stage, propagation stage, and finally the termination stage. Free radicals are terminated or neutralized by nutrients (antioxidants), enzymatic mechanisms, or by recombining with each other.

Related blog post links:

http://sciencedoing.blogspot.in/2013/05/oxidative-stress-strain-as-predisposing.html

http://sciencedoing.blogspot.in/2013/05/dark-oxidants-super-oxides-in-depth-of.html
http://sciencedoing.blogspot.in/2011/12/oxygen-necessary-evil.html
*Note: all pictures thankfully shared from various sources..