Free radicals are highly reactive compounds that are produced when the body uses oxygen. Environmental pollutants such as smog, radiation, cigarette smoke, herbicides, pesticides and many drugs can react within the body to cause production of free radicals. While free radicals are normal products of our cells and have certain beneficial roles in the body, excessive levels in body tissues can be detrimental to health. Free radicals multiply through a series of chain reactions and can damage both the structure and function of cell membranes. There is evidence connecting free radicals to the development of a number of degenerative diseases and accelerated Ageing.
Defence systems that protect the body from free radical damage include the Antioxidant nutrients and enzymes (antioxidants). Vitamin E is the major Antioxidant vitamin in body tissues and is considered the first line of defence against cell membrane damage. Other Antioxidant defences that protect the body from free radical damage include the enzymes superoxide dismutase (SOD), glutathione peroxidase, vitamin C, carotenoids, alpha-lipoic acid and bioflavonoids such as pycnogenol (from pine bark extract).
Approximately 40% of the factors affecting life expectancy can be controlled, which suggests not only that length of life can be extended but that quality of life can be enhanced through better health. One area of research suggests that free radical damage to cells leads to the tissue changes associated with Ageing. Oxidative stress (free radical damage) has been implicated in the development of various causes of disability in elderly people, including cognitive impairment and Alzheimer's disease, impaired immune function, cataracts and age-related macular degeneration.
It would be expected that centenarians (individuals that have reached 100 years of age), would have higher levels of free radical damage than younger individuals in their eighties or nineties. However it is thought that centenarians represent the best example of successful Ageing and have lower oxidative stress than subjects 70 to 99 years old. In a study of 82 subjects in Italy, byproducts of free radical damage and Antioxidant levels were compared in centenarians and aged subjects. Blood levels of the free radical by-products were lower in centenarians than in the aged subjects. In contrast, blood levels of vitamin C and vitamin E (Antioxidant nutrients) were higher in the centenarians than in the aged subjects, indicating that higher Antioxidant levels are associated with longer life expectancy. In a 12-month study in Poland, of 100 subjects, aged 60 to 100 years, supplementation with vitamins E and C decreased blood levels of free radical byproducts by 25 to 26%. In another study on elderly nursing home patients in Finland, there was a marked improvement in general mental condition after two months on vitamin E and selenium supplementation. This improvement continued throughout the one year study. Similar benefits from Antioxidant supplementation in the elderly have been demonstrated in many other studies.
Free radical damage has been implicated in brain Ageing and in certain degenerative conditions such as Alzheimer's disease and other forms of dementia. Recent research studies have investigated the association between Antioxidant levels and these conditions. The conclusions were as follows:
- In one study on elderly subjects, it was demonstrated that a lower intake of beta carotene was associated with impaired cognitive function. - A study of subjects aged 65 and older, concluded that impaired cognitive function was associated with lower dietary intakes and blood levels of vitamin C. - In a study on elderly people in Spain, it was shown that subjects with higher scores on cognitive function tests had higher intakes of beta carotene, vitamin C, vitamin E, folate, zinc, iron, fibre and carbohydrates. - It was concluded from a study of 65-94 year old subjects in Switzerland, that beta-carotene and vitamin C levels were significant predictors of memory performance. - In an Austrian study on 1,769 elderly subjects, it was demonstrated that vitamin E was significantly associated with cognitive performance.
Ageing is also associated with a progressive decline in the function of the immune system and an increased susceptibility to infection. It has been suggested that free radical activity associated with Ageing, may contribute to this lowered immune response, and that improved Antioxidant levels may have an immunostimulatory effect.
One 12 month Canadian study on a group of elderly subjects demonstrated a significant improvement in immune response in the Antioxidant supplemented group. Infection-related illness was much less frequent in the supplemented group than in the group on placebo. This result has been replicated in other studies. Another study demonstrated that supplementation of beta carotene restored immune activity in older men back to levels found in younger men.
Age is also considered a major risk factor in cataract development. The lens of the eye is very susceptible to light-induced free radical formation, and oxidation is believed to be an early and significant event in development of most cases of senile cataract. A number of studies have suggested a link between cataract incidence and Antioxidant status. In one study, high blood levels of vitamins E, C and carotenoids were associated with a significantly reduced risk of cataract development. Subjects with a high blood antioxidant status had an 80% decrease in cataract risk. This result has also been replicated in several other studies.
Macular degeneration is the leading cause of irreversible vision loss after age 50. Studies have shown that higher Antioxidant levels are protective against macular degeneration. The majority of research evidence suggests a beneficial effect of Antioxidants against development and progression of cataracts and age-related macular degeneration in the elderly.
Research suggests that free radicals have a significant influence on Ageing and age-related conditions. It seems that optimal intake of Antioxidant nutrients may contribute to enhanced quality of life and decelerated Ageing.
NOTESThe risks and benefits of Antioxidant supplements are not yet known. A diet containing a high amount and large variety of Antioxidants is better than taking Antioxidant supplements.