A young colleague sought me out recently to ask if there was anything she and her mother could do to help prevent dementia. Her grandmother on her mother’s side had Alzheimer’s disease, the leading type of dementia, and possibly her mother, too. Although dementia is not usually inherited (see www.alzheimers.org.uk), the increased incidence of this distressing condition worries many of us, particularly as two thirds of those diagnosed are women. According to Margaret Rayman, professor of nutritional medicine at the University of Surrey, there is evidence that eating well can significantly help our brain health, giving us the best chance of preventing dementia as well as heart disease, cancer and other diseases of ageing.

In her recent book, Healthy Eating to Reduce the Risk of Dementia, Professor Rayman and her team of experts review the evidence and give advice on diet and specific nutrients that can boost our brains and bodies, together with lots of recipes (I tried several and they are delicious). The overall message is that a Mediterranean diet is a ‘healthy and delicious way to combine all the different vitamins, minerals and all-important plant components’, she says. ‘In tests of cognitive function – including reasoning, attention, memory and language – people who eat a wide range of fruits and vegetables score highest; aim for six to seven portions a day [up to 500 grams]. The following foods in particular have been associated with beneficial effects on brain function.’

Salmon is packed with omega-3 fish oils, polyunsaturated fatty acids (PUFA s) that may slow cognitive decline and/or reduce dementia risk. Other good sources are dark tuna, herring, mackerel and sardines. All fish contain potentially brain-protective nutrients including vitamins B and D, selenium, zinc, iodine and taurine (an amino acid).

Olive oil, which is rich in monounsaturated fatty acids (MUFAs) and blood-vessel-friendly vitamin E, has been linked to sharper brain function. In a French study, people who used olive oil freely had a 17 per cent lower risk of decline in visual memory.

Avocado, the riper the better, contains a perfect balance of brain-healthy MUFA s and PUFA s plus a range of vitamins, minerals and plant nutrients.

Rapeseed oil contains a good balance of alpha and gamma tocopherol, two forms of vitamin E. Studies suggest a lower risk of dementia in up to a quarter of people with a high vitamin E intake from food (but not from supplements). Use for sautéing, frying and in salad dressings.

Pistachios and other nuts and seeds can improve the health of blood vessels, reduce blood pressure and improve blood flow. Pistachios are rich in key nutrients called polyphenols, vitamin E (as gamma tocopherol), vitamin C, betacarotene and selenium. Eat them raw or roasted and shelled (not salted).

Blueberries, blackberries, cherries, raspberries and other dark purple and red berries are rich in anthocyanins (a type of polyphenol), which may improve many aspects of brain function and also improve the function of blood vessels, which could in turn protect against vascular dementia (caused by narrowed or blocked blood vessels).

Oranges, lemons, grapefruit, mandarins and tangerines contain particular citrus flavonoids that provide flavour and colour and have potentially neuro-protective properties, as well as helping to reduce blood pressure and improve the health of blood vessels.

Green leafy vegetables are all good sources of folate, a B vitamin that, together with B6 and B12, could be especially important for a healthy brain. Kale, spring greens, cabbage, spinach and broccoli also help control levels of homocysteine, a chemical that is raised in people with dementia as well as stroke and heart disease. Find B6 in meat, fish, poultry, whole grains, potatoes and veg, and B12 in meat, offal, mussels, fish, milk, cheese and eggs.

Sun-dried mushrooms are a good source of vitamin D, which in addition to being important for strong bones may also help keep nerve cells healthy and improve heart health and immune function. In studies vitamin D deficiency is linked to a higher risk of cognitive impairment and poorer performance on tests of brain function (although this doesn’t prove it’s the cause). Buy sun-dried shiitake mushrooms or simply put ordinary button mushrooms in the sun for around half an hour.

• Healthy Eating to Reduce the Risk of Dementia by Margaret Rayman, Katie Sharpe, Vanessa Ridland and Patsy Westcott is published by Kyle Books, priced £14.99. To order a copy for £11.99 until 3 May, go to www.you-bookshop.co.uk; p&p is free for a limited time