Nutrition and Mental Health

Our brains are delicate organs sustained by a fine balance of fatty and amino acids, minerals and vitamins.

Virtually everyone of us has had the experience of a mood change if we become hypoglycemic, or sleepiness after eating chocolate or tryptophan-containing turkey. The scientific literature is full of reports about the impact of different foods and combinations of food on mood, alertness and cognition. Some of the links are not obvious. I was brought up with the old wives tale that children become sleepy after lunch or dinner because blood was being diverted to the intestines. Not so: sugary and fatty foods cause sleepiness by altering the secretion of insulin by the pancreas, which in turn effects the uptake of key amino acids in the brain, which in turn impact the synthesis of some neurotransmitters.

There has also been another yet more serious issue that has been turning up in the literature for decades, and that is the inter-relationships between diet, nutrition and mental illness. Epidemiological studies have found a clear relationship between the consumption of fish and the incidence and prevalence rates around the world: high fish consuming countries tend to have less depression. This relationship has held up in studies around the globe, so it is unlikely that it is simply that people living by the ocean in warm sunny countries are less likely to become depressed. These observations were part of what led Dr Andrew Stoll at Harvard to first study the impact of fish oils, containing omega-3 fatty acids, on mood. The results of the early studies were more impressive than the later ones, but the fact remains that fish oils have been helpful in a proportion of patients. The experimental work continues, in order to try and find the best and most effective mixture of fatty acids.

There is a theoretical reason why this might be: fish oils can change the characteristics of the membranes of many cells, including those in the brain, and thereby influence the firing and response of some neurotransmitters important in the maintenance of mood.

There have been recent reports from well-conducted studies of the impact on nutritional supplementation on reducing violence in prisons and that work is also continuing. The BBC has picked up on an eagerly awaited report from the Mental Health Foundation and Sustain. Called Feeding Minds this report by mental health advocates and food campaigners is ambitious and presents a good summary of the current state of the evidence, though its findings are sure to be controversial.

The report points out that changes in the composition of Western diets with the proliferation of industrialized farming and pesticide use and the depletion of some essential nutrients in the soil has coincided with a continuing increase in the incidence and prevalence rates of mental illness. It is always difficult to prove causality with research like this, since there have been many other social changes which could equally account for a rise in the rates of mental illness, to say nothing of ever-changing diagnostic criteria, that have sometimes labeled people with mental illness who would at one time have been described just as “different” or “eccentric” or “difficult.” But it is also fair to say that few people doubt the link between cigarette smoking and lung cancer, but to prove causality is bound to be difficult. This is very different from the situation with infectious diseases. Here we have had a set of four criteria which we can use to show whether or not an infectious organism is the cause of a disease. Known as Koch’s Postulates, which have guided us for 122 years and have so far been proven time and time again. These postulates have been modified over the years, yet still formed the basis of the work which lead to the 2005 Nobel Prize in Physiology or Medicine.

Sad to say, things are not so clear when looking at nutrition and mental illness. But let’s look at a few key items in the report:

1. Depression: I have mentioned this one already, and the report also emphasizes the link between depression and low consumption of fish that are high in omega-3 fatty acids

2. Schizophrenia: A link between some fatty acids and schizophrenia was first proposed by the late Dr. David Horrobin in the 1970s, and increasing epidemiological evidence has shown that sufferers have lower levels of polyunsaturated fatty acids (PUFA). There have been many studies which have attempted to modulate them to treat the disease, with some measure of success. Just this month there is a report in the British Journal of Psychiatry on the adjunctive use of PUFAs in the closely related condition of bipolar disorder.

3. Alzheimer’s disease: Some studies have suggested that a high consumption of vegetables, particularly those containing folate, can protect against or slow the progression of this brain disorder.

4. Attention deficit and/or hyperactivity disorder: Research shown that some children with these disorders are low in iron and fatty acids, though it is not so clear whether treatment with these agents will help these children.

In my book Healing, Meaning and Purpose, I talk at length about the dietary and other physical changes over the last 100 years, and this report adds more. In the last 50 years, our consumption of omega-3 rich fish has fallen by two thirds, and over the same time course we have dropped our consumption of vegetables by 34%. There is something else more subtle, that I did not see in the report. In the decades after the second world war, British children were routinely given daily cod liver oil tablets rich in omega-3 fatty acids, as well as free school milk.

The report makes a point that I have before in entries here: people cannot be held totally responsible for maintaining healthy diets: some food and farming policies have lead to a situation in which people may no longer have access to healthy and nutritious foods. And that will likely cause further increases in some mental illness. And artificial supplements can rarely replace the real thing.

The evidence base associating nutrient intake and mental health is in its infancy, but it is clearly an area that needs a great deal more attention.

The recommendations in the new report are eminently sensible, and few would quibble with any of them. Before making any nutritional changes, always discuss them with your health care provider.

I would like to make a final point that I am going to amplify elsewhere:

If any health intervention is good for you, it should help more than one system of the body. So a diet that is good for mental health should also be good for the health of blood vessels, heart and skin. A diet like Nicholas Perricone’s, that aims to help skin aging, should also be good for the brain and the cardiovascular system. This is always a good way of checking to see if something is good for you and whether to adopt someone’s advice.

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