Eating mushrooms could hold back the early signs of dementia.

Scientists found people who ate more than two 150g portions a week were half as likely to suffer mild cognitive impairment (MCI).

Mushrooms contain an amino acid which the body can't make for itself and which is found in particularly low levels in people with MCI, scientists said.

MCI is between natural brain decline and dementia, and people with the condition may experience forgetfulness and reduced language and attention skills.

Researchers at the National University of Singapore interviewed more than 600 Chinese over-60s over the course of six years about their diet and health.

The participants also took part in tests to work out how well their brains function and give them a 'dementia rating' to asses how much their minds had been damaged by age.

Those who ate more than two portions of cooked mushrooms each week were up to 50 per cent less likely to have mild cognitive impairment.

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Although 300g of mushrooms may sound like a lot, the researchers believe even one small portion could still be beneficial for reducing the risk of MCI.

Feng Lei, one of the researchers, said: "This correlation is surprising and encouraging.

"It seems that a commonly available single ingredient could have a dramatic effect on cognitive decline."

Although people with MCI can usually still carry out day-to-day activities, their mental abilities are worse than would be expected for their age.

It isn't a type of dementia but people with MCI – about five to 20 per cent of over- 65s in the UK – are more likely to develop dementia.

Dr Irwin Cheah said: "We’re very interested in a compound called ergothioneine (ET).

"ET is a unique antioxidant and anti-inflammatory which humans are unable to synthesise on their own.

"But it can be obtained from dietary sources, one of the main ones being mushrooms."

The mushrooms mentioned in the research were white button mushrooms and the oyster, shiitake and golden varieties, as well as dried and canned mushrooms.

It is estimated between five and 20 per cent of over-65s in the UK have MCI.