The brain is one of the largest organs in the body and, like our hearts, livers and other organs, it is affected by what we eat and drink. However, unlike with other organs, the links between diet and the brain - and hence how we think and act - are not yet widely recognised.
Despite a large number of peer-reviewed and published research studies, scientific understanding of how food affects mental health is far from complete. However, it is already clear that our diets affect how our brains are made and how they work throughout our lives, from foetal development to old age. The significance of diet for mental health and well-being varies, but there appears to be no point in the human life-cycle at which diet has no effect.
There are some important nutrients for brain development and function, but they can only work properly if a wide range of other nutrients are also available in the right amounts and in proportion to each other. There is no "magic bullet" or single nutrient that holds the key to mental health and well-being.
The combination of nutrients that is most commonly associated with good mental health and well-being is as follows:
- polyunsaturated fatty acids (particularly the omega 3 types found in oily fish and some plants);
- minerals, such as zinc (in whole grains, legumes, meat and milk), magnesium (in green leafy vegetables, nuts and whole grains), and iron (in red meat, green leafy vegetables, eggs and some fruit); and
- vitamins, such as folate (in green leafy vegetables and fortified cereals), a range of B vitamins (whole grain products, yeast and dairy products), and antioxidant vitamins such as C and E (in a wide range of fruit and vegetables).
This is, of course, the same type of healthy balanced diet that is widely recommended to reduce our risk of developing coronary heart disease, strokes, a range of cancers, diabetes and a number of digestive disorders and conditions.
People eating diets that lack one or more of this combination of polyunsaturated fats, minerals and vitamins, and/or contain too much saturated fat (or other elements, including sugar and a range of food and agricultural chemicals) seem to be at higher risk of developing the following conditions:
- Attention-deficit/hyperactivity disorder (ADHD)
- A range of depressive conditions
- Schizophrenia
- Dementia, including Alzheimer's disease
The evidence so far does not show that these conditions can be prevented or cured by diet alone. However, evidence is accumulating that the combination of polyunsaturated fats, minerals and vitamins may help to:
- relieve the symptoms of some mental illnesses;
- improve the effectiveness of medication for some conditions; and
- reduce the unpleasant side-effects of some medications.
The diet that would give us the right amount and balance of these nutrients would contain:
- lots of different vegetables and fruit,
- a wide variety of whole grains, nuts, seeds and legumes,
- and some occasional oily fish, lean meat and dairy products.
Food, mental health and evolution
It makes evolutionary sense that this type of diet would be good for both our physical and mental health. When food supplies were plentiful, our ancestors would have eaten broadly this kind of diet. Unfortunately that is not what most of us are eating now.
The agricultural and industrial revolutions, followed by the globalisation of world food trade mean that most people in rich countries (and growing proportions in poor countries) eat:
- small amounts of a few types of vegetables and fruit;
- very few whole grain products - our carbohydrates are mostly refined (such as sugar and products made from white flour) - and from very narrow range of cereals (90% of the calories from cereals eaten in the UK are from wheat);
- very little oily fish,
- but large quantities of intensively produced meat, meat products and dairy products;
- unknown (and possibly unknowable) combinations of food and agricultural chemicals, either as intentional additives or accidental residues.
As a result, instead of our diets providing a healthy combination of polyunsaturated fats, minerals and vitamins, we are eating too much saturated fat, sugar and salt and not enough vitamins and minerals. Our analysis of the research indicates that this diet is fuelling not only obesity, cardiovascular disease, diabetes and some cancers, but may also be contributing to rising rates of mental ill-health and anti-social behaviour.
