But eating your greens is good for the brain

Eating your greens is not just good for you in the short term - it may also save your mental powers in later life.

Cruciferous vegetables, such as broccoli and cauliflower, and leafy foods such as spinach, may help to stem the decline in memory and reasoning powers.

And it's never too late to start. In a U.S. study involving 14,000 women nurses, researchers found that those who ate plenty of greens in their 60s suffered less mental decline in their 70s.

Leafy and cruciferous vegetables contain antioxidants and B vitamins which are believed to protect the brain.

Meanwhile, obesity, high cholesterol or high blood pressure have been found to push up the risk of Alzheimer's disease.

A Swedish study of middle-aged people showed that the risk roughly doubled for each condition suffered. Those who had all three were six times more likely to develop dementia than those who had none.

Researchers in Sweden also found that people who were physically active - by going walking and gardening - and stayed mentally active by going on courses or to the theatre were at lower risk of dementia.

Alzheimer's affects 700,000 Britons. There is no known cure.