FREE RADICALS, OXIDATION AND ANTIOXIDANTS
By Kevin Witham, BSc(Hons), MDipFTST, DipIIST, NLP(Prac)
It is now widely accepted that exercise has many health promoting benefits including lowering blood pressure and cholesterol which reduces the risks of coronary heart disease, increasing bone density and improving insulin usage which helps reduce osteoporosis and diabetes all epidemic in western societies.
Increasingly however, research is also linking exercise with increased production of damaging chemicals called Free Radicals which may cause a variety of diseases such as cardiovascular disease, auto-immune disorders and even the ageing process itself.
In the 1950s Dr. Harman started to study the effects of radiation on mice and noted that the animals exposed to it aged more quickly and died younger. Harman thought that the radiation may be producing some highly reactive or rogue ‘free radical’ that may be causing the damage. It was Dr Harman who first proposed that we get old due to free radical damage. At the time the work received little interest until further research in the late 1960’s.
A Free Radical is strictly defined as 'an entity with one or several unpaired electrons in the outer electron orbit of an atom or molecule'.
This explanation may sound a little confusing but is in essence fairly simple. Every atom contains a nucleus which is comprised of neutrons and protons The Protons carry a positive electrical charge the neutrons no charge. Around the outside moving at great speeds are electrons in distinct energy orbits or shells which carry a negative charge. In Nature chemistry seeks to find a balance so a balanced stable atom or molecule would have equal numbers of Protons and Electrons to equal out the electrical charge. In a chemical reaction this balance may be changed and leave an unpaired electron. With unequal numbers of protons and electrons the atom is unbalanced and must achieve stability.
This unbalanced molecule or ‘fragment’ is now highly reactive and unstable as the molecule seeks to find a spare electron. This may cause damage and create further free radicals. This chain reaction may continue for several days.
Free radicals are produced in the body in a number of ways but a big contributor especially for regular exercises is oxygen. This has led to the idea of the ‘oxygen paradox’ Oxygen is absolutely vital for life and yet oxygen is also unstable and is a major source of Free Radical production.
Energy is produced in the body by breaking down the food that we eat with oxygen - a process of oxidation to produce the energy molecule adenosine triphosphate (ATP), water and carbon dioxide.
FOOD + OXYGEN = ENERGY + CARBON DIOXIDE + WATER
The above reaction occurs by controlled oxidation which in 95% of the time is a clean reaction producing no free radical damage. But, in the other 5%, energy is produced by univalent reduction which produces a mass of free radicals.
Examples of the damaging effect of oxygen or oxidation include the rusting of untreated metal the browning of a cut apple and the rotting of meat. Inside the body the radicals can attack cell membranes leading to wrinkles and skin diseases such as eczema and psoriasis. Arterial walls can be damaged perhaps leading to the beginning of CAD and double bonds found in unsaturated fats and in DNA itself are easier attacked possibly leading to cancer and arthritis. The damage caused by free radicals is also the major source of the continued muscle soreness or DOMS felt for several days after intense exercise. Further, links have also been made between free radicals and Alzheimer’s disease, Diabetes, Hypertension, Rheumatoid Arthritis, Mental Illness and Macular degeneration. It is worth noting that some free radicals are useful as our immune system produces them to kill harmful microbes.
The problem for us is that exercise can create an 10-15 fold increase in oxygen consumption and along with it increased free radical damage. It has been shown that there is a three fold increase in muscle free radicals with only moderate intensity exercise. Add to this other causes of free radical damage, including temporary tisÂ≠ije poa ri?g heavy resistance training, muscle injuries and environmental factors such as too much sunlight, alcohol, smoking and pollution. Indeed, the radicals produced in tobacco smoke can remain active for days.
The human body evolved to utilise oxygen than it has also evolved some defenses to shut the free radicals down. These come in the form of antioxidant enzymes which the body produces, mainly superoxide dismutase, catalase and glutathione and very importantly dietary antioxidants acquired from the food that we eat. People with poor diets depleted of nutrients may be at greater risk as the body’s antioxidant enzymes require nutrients such as Vitamins A,C,E and minerals Zinc, Selenium, Copper and Manganese to function properly.
Antioxidants are substances that slow oxidation by neutralising free radicals and work by being able to donate or receive electrons. The antioxidants which are most familiar are Vitamin C, Vitamin E and Carotenoids (pigments which colour vegetables such as carrots, spinach and tomatoes). Flavonoids are another group which include compounds found in tea, wine and beer. Many new chemicals are being discovered all the time and plant nutrients known as phytonutrients are thought to play a protective role.
Research suggests that regular exercisers do have a much higher level of their natural antioxidant enzymes to help protect them however, with intense or long duration training the huge amount of oxygen produced will overwhelm your body’s defenses especially combined with environmental factors.
Although the use of supplementation remains controversial in raising levels of dietary antioxidants, some interesting research has emerged. Firstly, it is unclear whether many people especially regular exercisers can obtain enough nutrients from modern processed diets. In America, work by the US National Academy of Sciences have showed that already degraded crops may lose even more nutrients between harvesting and the table meaning many people were not even getting the basic RDA of many nutrients.
Here are some reported benefits of antioxidant supplementation.
Vitamin C. (Found in fruit, especially citrus such as oranges, lemons and grapefruit, and also in green vegetables, peppers, tomatoes and potatoes).
Perhaps the most famous antioxidant research has shown that vitamin C can help lower blood pressure and cholesterol and researchers have found that people who suffer from asthma, arthritis, cancer, diabetes and heart disease have lower levels of this vitamin in their blood than non-sufferers. Other studies have shown Vitamin C to aid recovery and reduce soreness and damage associated with unaccustomed exercise and there were fewer reported upper respiratory tract infections in runners. However, it is still unclear whether direct supplementation of Vitamin C produces similar results.
Vitamin E. (Found in vegetable oils, margarine, egg yolk, wholegrain cereals, almonds, nuts and green leafy vegetables).
Has been shown to protect red blood cells from oxidative stress during intense exercise and to protect against free radical induced muscle damage. Vitamin E also seems to reduce damage from intense, eccentric exercise.
Working in conjunction with vitamin C, vitamin E is a potent antioxidant and some studies show that vitamin E might prevent or even slow the progression of arterial plaques if you already have heart disease. Other studies, however, have found no benefit from vitamin E supplementation in high risk heart patients.
Zinc. (Found in oysters, ginger root, lamb, nuts, haddock, green peas, eggs and grains). Is known to be a co-factor for the antioxidant enzyme, superoxide dismutase, and seems to block the exercise-induced increase in free radicals. Zinc is also known to be critical for immune cell production and proper functioning of B and T cells.
Lycopene. (Found in tomatoes and related tomato products).
This carotenoid, found in tomatoes, is one of the most powerful antioxidants and has been shown by a study by the Harvard School of Public Health to cause a 45% reduction in prostate cancer in men who eat 10 or more servings of tomato-based foods a week. It may also be protective against many other disease such as cancers of the mouth, pharynx, esophagus, stomach, colon and rectum.
Beta Carotene. (Found in carrots, cantaloupes, pumpkins, sweet potatoes and tomatoes).
Another carotenoid, beta carotene, has been associated in some studies with a lower risk of heart disease. A Japanese study on 265,000 people found a significant correlation between low beta-carotene intake and the incidence of lung cancer. Not all reported studies have been positive, however. One study by the National Cancer Institute gave smokers beta-carotene and reported a 28% increased incidence in lung cancer. Other studies have also found that supplements of beta-carotene offered no protection against heart disease.
Selenium. (Found in cereals, meat, fish brazil nuts, shellfish, tuna and dairy products).
Found in a number of enzymes, some of which are antioxidants, and works together with vitamin E helping to protect cells against free radical damage. Deficiency of this mineral was first discovered in China as the cause of ‘Keshan disease’ a type of heart disease which occurred in areas where the soil was low in selenium. It has also been associated with a lower risk of certain kinds of cancer. In extensive animal studies selenium inhibits development of induced cancers of the breast, liver, skin and colon.
The list goes on of the potential benefits of antioxidants and supplementation in their role in limiting free radical damage which is now widely accepted as a cause of degenerative diseases - we essentially get diseased and die due to wear and tear. As we get older we lose the battle against the environmental damage from radiation, pollution and increasingly poor diets. Exercise also increases oxidative stress through increased oxygen consumption so it is important to stress that those engaging in regular and especially intense exercise need to ensure that their diet is better than the average to ensure high nutrient densities. This should help limit any damage caused by exercise, including injuries, and help promote recovery caused by myofibril damage - DOMS.
Although not all the research with supplementation is favorable, one thing is agreed among researchers. Consumption of a diet rich in fruit and vegetables is recommended as a protection against the risks of developing a number of degenerative diseases associated with ageing, including cardiovascular diseases and cancer. It is thought that since fruit and vegetables are a rich source of compounds called phytonutrients that have antioxidant properties, they may assist in reducing the harmful effects of free radicals. For example, known flavonoids - a group of antioxidants found in plants - number over 20,000 but only 4,000 have so far been chemically analysed or tested. It may well be that some of the conflicting research on the benefits of antioxidants comes from the fact that nutrients work together - they enhance each other's potency. In this case ensuring adequate levels of all the many thousands of different chemicals found naturally in foods is far more effective than taking tablets which can only contain a limited number of chemicals found widely in nature.
Finally, in America, 80% of the population do not consume the recommended 2-3 servings of fruits and the 3-5 servings of vegetables each day. Increasingly the processed, convenience culture is leading to poorer nutrient foods and overall diets. It is therefore vital that we encourage a fresh wholefood diet in the battle against free radical damage and improve our health and exercise performance.