A healthy diet beats dietary supplements
An article on the myths attached for decades to some of the antioxidant supplements consumed in efforts to maintain good health appears in the 5 August issue of New Scientist. It is estimated that half the
adults in the US take antioxidant tablets daily to stave off disease.
Nevertheless, writes Lisa Melton in the article, recent evidence suggests
that such efforts are of doubtful value.
Back in the 1950s it was discovered that heart disease, strokes, cancer,
diabetes, cataracts, arthritis and neurodegenerative diseases were linked
to free radicals acting on proteins, carbohydrates, lipids and DNA. But
breathing inevitably exposes us to free radicals.
In the 1980s it was understood for many years that people taking a diet
rich in fruits and vegetables showed a lower incidence of heart disease,
diabetes, dementia, stroke and certain cancers than others and this suggested
that the antioxidants present in green plants neutralised free radicals
by donating electrons. Such a discovery promoted a massive industry concerned
with producing antioxidants for dietary supplements.
The best known antioxidants were tocopherol, ascorbic acid, flavonoids
and carotenoids. Although these counteracted free radicals in the test
tube, they were less effective once they had entered body tissues.
Treatment with beta-carotene was recommended to protect smokers against
lung cancers, but it was found to have the opposite effect.
Tocopherol became popular in the early 1990s for reducing heart disease,
but was later discredited. It failed to halt the progression to Alzheimer’s
disease in people with mild cognitive impairment.
Ascorbic acid apparently only prevented free radical damage in individuals
with an existing vitamin C deficiency.
Polyphenols are powerful antioxidants, but their absorption into the
blood and metabolic rate remains obscure.
The conclusion is being reached that a diet rich in fruit and vegetables
has health benefits, but cannot necessarily be paralleled by taking vitamins
and other dietary supplements. The fact that heart attacks, vascular
disease, diabetes and cancer are reduced by a healthier lifestyle with
more exercise may account for the phenomenon of the apparent beneficial
effects of nutritional supplements./p
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At the annual meeting of the Human Behaviour and Evolution Society, held in Philadelphia early in June, it was suggested that, although life may have been nasty and brutish for our prehistoric ancestors, it may often have been longer than we have hitherto supposed. There used to be a belief
that it was rare for someone in prehistoric society to reach the age
of 40 but today it is thought from a study of modern hunter-gatherer
groups that a substantial proportion of our remote ancestors survived
into their 70s.