There appears to be no respite in the pace or impact of the growing burden of mental ill health on individuals and the nation as a whole. One in four people is likely to experience a mental illness at some point in their life, and the costs of mental ill health to the UK economy are now approaching £100bn a year.

Mental health problems are believed to be the result of a combination of factors, including age, genetics and environmental factors. One of the most obvious, yet under-recognised factors in the development of major trends in mental health is the role of nutrition.

But the body of evidence linking diet and mental health is growing at a rapid pace. As well as its impact on short and long-term mental health, the evidence indicates that food could play an important contributing role in the development, management and prevention of specific mental health problems such as depression, schizophrenia, attention deficit hyperactivity disorder, and Alzheimer's disease.

The increasing incidence of mental ill health echoes changes in food production in the UK. The last 50 years have witnessed significant changes to the way food is produced and manufactured. The proliferation of industrialised farming has introduced higher levels and different types of fat into our diet.

Chickens now reach their slaughter weight twice as fast as they did 30 years ago, which has changed the nutritional profile of the meat. Whereas a chicken carcass used to be 2% fat, it has now risen to 22%. Also, the diet fed to chickens has changed, which has reduced omega-3 fatty acids and increased omega-6 fatty acids in chicken meat. Similarly, the diet fed to farmed fish is changing the ratio of fatty acids in the fish we eat. As a result, the population's intake of omega-3 fatty acids has decreased whilst the consumption of omega-6 fatty acids has increased. This unequal intake combined with a lack of vitamins and minerals has been linked depression, concentration and memory problems.

At the same time, the UK population is consuming less nutritious, fresh produce and more saturated fats and sugars. Over the last 60 years there has been a 34% decline in UK vegetable consumption with currently only 13% of men and 15% of women now eating at least five portions of fruit and vegetables per day. New substances, such as pesticides, additives and trans-fats have been introduced to our diets. Alone and together, these substances can prevent the brain from functioning effectively.

A poll carried out by the Mental Health Foundation found that:

· Women eat healthy foods, including fresh vegetables, fruit or fruit juice and meals made from scratch, more often than men, who tend to eat more takeaways and ready meals.

· Two-thirds of those who do not have daily mental health problems eat fresh fruit, vegetables or juice every day, compared with less than half of those who do report daily mental health problems.

· Younger people are more likely than older people to experience daily mental health problems.

Foods can have an immediate and lasting effect upon a person's mental health and behaviour because of the way they affect the structure and function of the brain. While most people are aware of how diet affects their physical health, fewer understand that the brain, as an organ, is affected by the foods they eat, and how this has a knock on effect on their mental health.

While some foods damage the brain by releasing toxins or oxidants that harm healthy brain cells, there are many more nutrients that serve the brain without deception or damage, which can improve mood and mental wellbeing. Dietary interventions may hold the key to a number of the mental health challenges our society is facing. Yet little investment is being laid out to develop this knowledge, and only a tiny - but growing - number of professionals are putting it to effective use.

In May 2005, a team at the Doncaster and South Humber NHS trust was set up to help young people experiencing their first episode of psychosis. The team helps the young people by improving their nutrition, with the aim of preventing the physical complications of schizophrenia and improving their mental state. All young people are given a full nutritional assessment and analysis. Where a person has nutritional deficiencies in their diet, they are given omega-3 fatty acids, multivitamins and mineral supplements. Those with poor diets are advised to reduce their intake of saturated fat and sugar. Young people are then encouraged to eat a balanced diet, to reduce the need for supplements and follow an exercise programme.

Growing evidence indicates the benefits of dietary interventions to support a person's recovery from mental health problems. But financial investment is now needed to further this understanding and develop appropriate interventions to help people manage mental health problems including depression, dementia, attention deficit hyperactivity disorder and schizophrenia.

The Mental Health Foundation has joined forces with the Sustain, the alliance for food and farming to raise awareness of the links between nutrition and mental health. We are calling on the government to recognise these links and to increase financial and political support to ensure that a variety of nutrient-rich foods are available for people to buy in the UK. We are also hoping that the government will improve the quality of food provided to people with mental health problems, with appropriate support and guidance for mental health service providers.

· Fran Gorman is public relations manager for the Mental Health Foundation