Can a better diet really help improve mental health?

A report published last week held out hope for a simple, cheap and effective treatment for various mental health problems.

The study, by the Mental Health Foundation and food campaign group Sustain, suggests diet could have an immediate and lasting effect on mental health.

It links changes in the human diet over the past 60 years, such as increased consumption of processed food and reduced consumption of vegetables, with the country’s worsening mental health.

The dry weight of the brain is composed of about 60 per cent fat so, the report argues, the fats we eat directly affect the structure and substance of the brain cell membranes.

And the neurotransmitters, which pass messages around the brain, are made from amino acids, many of which have to be derived directly from the diet. A deficiency in some amino acids can lead to feelings of depression, the report adds.

The authors conclude that the evidence linking mental health and diet is growing rapidly and shows nutrition’s “contribution to the development, prevention and management of specific mental health problems”.

Charity Counsel and Care argued last month for a Jamie Oliver-style campaign to improve food in care homes. But does the science justify such a campaign for mental health services?

Caroline Stokes, a research nutritionist for mental health at Doncaster and South Humber NHS Trust, already offers dietary advice to people with mental illnesses and believes it has been effective.

She says: “I’ve worked with people with long-term depression and people with the first onset of psychosis and in both cases I’ve seen differences, and particularly with depression.”

She says the evidence base is relatively strong for some substances, such as omega-3 fatty acids, found in oily fish, folic acid, found in leafy green vegetables, and selenium, found in Brazil nuts, which are all thought to tackle depression. However, she says it is less strong for others and calls for more research.

British Nutrition Foundation scientist Joanne Lunn says the nutritional recommendations in the report – plenty of fresh fruit and vegetables and oily fish – are in line with what would be considered a healthy diet anyway.

But she believes there are problems with studies that measure subjective values such as mood and says most of the evidence linking food and mental health is anecdotal.

Similarly, Peter Rogers, professor of biological science at Bristol University, says diet could be important in relation to mental illness but scientific evidence suggests the subject should be treated with caution.

Studies are needed in which people change their intake of nutrients and the results are measured – but at the moment we are “in the early stages” of such studies, he says. And the outcomes of research in which he has been involved have been “a bit mixed”.

“It doesn’t really hit you between the eyes that there’s an amazingly strong effect here,” he says.

David Christmas, clinical lecturer in psychiatry at Dundee University, says some studies have shown the effectiveness of dietary supplements, but many of the studies were small and supplements were often used alongside other treatments.

Another problem, he argues, is that, because nutrients are not supported by the drug companies, there is little money to conduct large enough trials to be definitive.

“While the evidence is not conclusive,” he says, “there is sufficient evidence to be optimistic that compounds such as omega-3 fatty acids may have a place in treating some patients. The advantage is that they may be more acceptable to many individuals than other [drug] options.”

Christmas concludes that dietary treatments would be an attractive proposition for many because they are cheap, with the patient footing the bill, have positive physical health benefits and allow people a sense of control over their treatment.

But, he says, although the evidence base is increasing, dietary treatments are unlikely to work for everyone and scientists have yet to establish for whom they will be most effective.

Rogers believes that public opinion is probably ahead of scientific evidence on nutrition and mental health, perhaps because it seems such an easy option.

“It’s an attractive solution but in my view there’s not really the evidence that it is a magic bullet.”

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