When, in 1992, Amanda Geary was diagnosed by her GP as suffering from depression, she was prescribed the usual treatment antidepressants and cognitive behavioural counselling. She continued with the counselling for eight months, but stopped taking the medication after a month, having noticed no improvement.
When, after a year, her symptoms had not improved, she was referred to a consultant neurologist who diagnosed ME or chronic fatigue syndrome. A registered nutritional therapist, Geary decided to change her diet in the hope her condition would improve. "It was only when I changed my diet, and cut out wheat, that I noticed an obvious improvement in my depression. Now, if I do have some wheat, I notice a depressing effect, I become tired and sluggish. I have seen that effect many times with clients. I now have no doubt that what we eat and drink has an important part to play in how we feel mentally and emotionally as well as physically," she says.
Geary, whose Food and Mood Handbook has just been published, believes that those who ignore a link between food and mood do so at their own cost. "A change in diet can have very large changes," she says. "People can find that certain symptoms such as anxiety, panic attacks, irritability and aggression that they thought were part of their personality in fact turn out to be the biochemistry of their brain that is being influenced by the food they were or weren't eating. An extreme form is criminal behaviour. There is now quite a bit of evidence that suggests that criminality is affected by diet, and well-controlled experiments have been done on the inmates of prisons. Because every infringement of a regulation is recorded in jail you can see the change in the number people are making. And that has gone down dramatically when diets have changed.
"It's important that people start to make the link, because not being aware can cause unnecessary suffering, and a simple change in diet seems to be able to help so many people, and potentially save a lot of expense in terms of medical treatment and time off sick from work."
In 1998, Geary founded the Food and Mood Project, with the help of a Millennium Award from Mind, the mental health charity. The project involves Geary teaching courses for women, exploring the relationship between what they eat and how they feel. Geary says food can be broken down into good or bad mood carbohydrates, proteins, and fats. Good mood slow-releasing complex carbohydrates should take the place of bad mood fast-releasing refined carbohydrates such as sugar, white bread, cakes and biscuits.
"The problem with sugar for people who are sensitive to it is that when they eat these fast-releasing sugars or carbohydrates they get a dramatic rise in blood-sugar level, and that then stimulates the pancreas to release insulin, which is then followed by a blood-sugar dip. And that is associated with symptoms of confusion, irritability, aggression, as well as physical feelings of fatigue and tiredness."
Good-mood proteins have a positive effect on chemicals in the brain associated with mood, says Geary. Serotonin (low levels of which can be responsible for feelings of depression) in the brain is made from tryptophan, an amino acid found in protein-containing foods. "Therefore, eating tryptophan-containing foods is one way of potentially boosting brain serotonin levels." Foods that are particularly high in tryptophan are poultry, oil-rich fish, beans, baked potatoes, oats, nuts and seeds.
Dopamine and noradrenaline, important for staying alert and active, are two other important neurotransmitters that can be boosted by good-mood proteins. "Lower levels of dopamine and noradrenaline can result from low levels of the amino acids tyrosine and phenylalanine, which are needed to make these neurotransmitters. Low levels of tyrosine have been associated with depression where apathy and lack of motivation are key symptoms." Protein-rich foods containing tyrosine and phenylalanine include meat, fish, beans, nuts, seeds, soya and cheese. Geary suggests eating these foods at lunchtime.
Bad-mood protein would be meat containing high amounts of saturated fats. "Fats matter a lot to emotional and mental health, with low levels in the diet being associated with symptoms that range from anxiety and depression to hyperactivity and schizophrenia," says Geary. "Too much saturated fat can affect the metabolism of the healthier fats which you do need, which are the unsaturated fats."
Of particular importance for emotional and mental health are the omega-3 essential fats, plentiful in oil-rich fish such as mackerel, herring, pilchards, sardines, salmon and fresh tuna. "People need a dose of these fish three times a week. Linseed oil, which can be added to food every day, is the best alternative for vegetarians."
Geary says her claims are backed up by scientific research. She admits, however, that there is no scientific proof that wheat can cause depression, or indeed that dairy products and yeast can, which she also cites. "I'm not aware of any studies that link these foods to depression specifically; the evidence is clinical rather than experimental, but there is clinical evidence."
Other foods commonly linked with mental and emotional symptoms include oranges, tomatoes and corn. "The precise cause-and-effect relationship between different foods and moods has yet to be scientifically established, although individuals often find that they can associate certain foods with moods." The effects of changing diet can be immediate, she claims. Those who swap white toast for brown at breakfast may notice a difference at once. "Most people can report a change within a few days."
But Dr Peter Rogers, senior lecturer in experimental psychology at Bristol University, who specialises in nutrition and behaviour, says: "Within the normal day to day variations in our diet we are not going to pick up big physiological effects on mood.
"Another way of looking at it is to think: 'Why should the brain be so sensitive to changes in our diet?' It's not a very adaptive thing to be happening if a subtle change in your diet can alter strongly how you feel or behave. We shouldn't expect there to be very strong effects. One of the ways in which eating has the biggest impact on how we feel in terms of mood and emotion is actually not really mediated directly by physiological affects, it's more to do with our psychological relationship with foods such as the fear of food making us fat, or perhaps giving us heart disease."
There is no research that convinces him we should be eating certain foods at certain times of day to boost mood. "There are claims that high carbohydrate meals can relieve depressed mood and perhaps make you feel relaxed. However, in the studies that have shown that, the effects are fairly subtle, but if they are there they are only there if you eat meals that are almost completely carbohydrates, and it's virtually impossible to do that, unless you are drinking large amounts of sugar in a drink. Most real foods, even pasta and bread, are served with protein, and a small amount of protein can remove any effects of carbohydrates in the brain. With real foods, and real diets, food we'd actually want to eat and enjoy eating, probably it's not possible to get substantial mood effects through those means; certainly not mood effects of the magnitude that would be particularly noticeable, or would compare with the effects of anti-depressant drugs, for example."
Dr Louise Dye, senior lecturer in biological psychology at Leeds University, says: "The effects of food on mood are subtle and are probably as likely to be produced by the taste and liking for the food as they are to be the result of a change in brain chemistry."
Certain foods may well affect mood when included in a diet already deficient. Margaret Rayman, of the Centre for Nutrition and Food Safety at Surrey University, says some studies have shown a beneficial effect of the trace element selenium, found in soil-grown crops. "Low selenium status was associated with significantly greater incidence of depression and other negative mood states. The mood of people on a low selenium diet significantly worsens, while that of people on a high selenium diet significantly improves." Dr Rayman says less selenium has been eaten in Britain since wheat flour imports from North America were reduced in favour of European wheat. Other selenium-rich foods include shellfish, kidney, liver and Brazil nuts.
'The Food and Mood Handbook' by Amanda Geary is published by Thorsons at £9.99
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