Eating too much junk food may contribute to cancer, dementia, stroke and other diseases through a lack of vitamins, minerals and other micronutrients in the diet, according to a new theory.

Professor Bruce Ames, of the Children’s Hospital of Oakland Research Institute, California, believes that many common disorders associated with ageing can be traced in part to poor diet earlier in life.

The research that he presented to the conference yesterday suggested that taking regular multivitamin supplements could protect against some bad effects of micronutrient deficiencies.

This idea is contradicted by other studies that have shown little benefit to health in taking vitamin and mineral supplements, suggesting that they are no substitute for a balanced diet rich in fruit and vegetables.

Professor Ames emphasised that his idea was theoretical and he accepted that much more work into the effects of supplements was needed to provide sound medical advice.

He said that shortages of 15 micronutrients, including magnesium and vitamin D, had been associated with greater levels of DNA damage to cells and a raised risk of cancers.

Fifty-six per cent of Americans obtained less than the recommended daily amount of magnesium from their diets; 12 per cent consumed insufficient zinc; and most African-Americans were deficient in vitamin D, which was mainly synthesised by exposure to sunlight and was often lacking in people with dark skins who were living at higher latitudes.

“Most of the world’s population, particularly the poor, has inadequate intake of one or more micronutrients that a varied and balanced diet should provide,” he said. “Social concern is low because no overt pathology has been associated with these levels of deficiency.”

Whereas serious vitamin or mineral deficiencies had symptoms, such as scurvy for vitamin C and ricketts for vitamin D, mild shortages generally had none. Professor Ames said that it was possible that the body compensated for such shortages by rebalancing metabolism, so that individuals stayed alive for the short term at the cost of their long-term health.

“The consequences of this homoeostatic response are, for example, DNA damage (future cancer), adaptive immune dysfunction (future disease), and mitochondrial decay (future cognitive dysfunction and accelerated ageing),” he said.

“Much evidence supports this idea that micronutrient shortages accelerate ageing.”

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