Nutrition in Mental Health - Sounding the alarm
In general medicine the alarm has been sounded about the health effects of the post-industrialisation Western diet on our bodies and our minds.
There has been a move from whole foods to processed foods favouring durability, transportability, palatability and convenience over nutrition. There is little dispute about the associations between diet and chronic disease including cardiovascular disease, myocardial infarction, type II diabetes, cancers and obesity. Now that same alarm is being sounded in mental health as epidemiologic, basic scientific, and clinical evidence show that diet both influences risk for, and outcomes of mental health disorders.
Deficiency of B12 and folate have been known to be a cause of depression and cognitive dysfunction for some time. But gross deficiency is not the only means by which diet might affect mental health. It is becoming clear that psychiatric disorders share many of the same disease pathways as chronic medical problems including immune dysregulation, chronic inflammation, oxidative stress, mitochondrial dysfunction, alterations in the gut flora (microbiome), and epigenetic changes, perhaps helping to explain the high rates of psychiatric comorbidity with obesity, cardiovascular disease, autoimmune disorders and type II diabetes.
It is now known that the Western diet can drive pathophysiological change at each of these pathways and is a risk factor for the development of depression (throughout the life course including prenatal maternal diet affecting the risk of internalising and externalising behaviour in offspring), anxiety and may play a role in increasing the risk of developing psychosis in high risk individuals.
A series of large population studies from Scandinavia, Spain and Greece showed a clear association between depression and anxiety and diet quality, with a whole food, mediterranean style diet having the lowest risk. Similar studies have demonstrated similar inverse relationships between depression and diet low in processed foods in Asian populations. One recent neuroimaging study demonstrated an inverse relationship between hippocampal volume and diet quality in older adults. Furthermore these studies were controlled for a range of confounders including age, sex, socio demographic status, smoking and education levels. Several prospective trials have begun to address the issue of reverse causality. Unfortunately clinical trials of dietary interventions in psychiatric disorders are methodologically complicated, particularly in maintaining adherence to the dietary intervention and due to the nature of cognitive and behavioural changes in psychiatric disorders.
The number of clinical trials on individual nutraceuticals in psychiatric disorders is also growing. A trial of omega 3 essential fatty acids in young people at high risk of developing psychotic disorders demonstrated a significant protective effect reducing risk of progressing to a psychotic disorder from 40% to 3%. Animal trials have showed transplanting bowel flora from anxious mice to non-anxious mice (after sterilisation of their own bowel flora) induced similar anxiety states and giving probiotics to healthy men helped reduce physiologic and psychological stress with modest improvements in cognitive function.
Nutrients of particular interest in psychiatric disorders include omega 3 essential fatty acids, B vitamins, choline, minerals such as zinc and magnesium, pre and probiotics, S-adenosyl- Methionine (SAMe), a variety of plant chemicals with anti-inflammatory and antioxidant properties such as curcumin, the yellow pigment found in Turmeric or the compounds known as polyphenols including resveratrol.
While conducting intervention trials for dietary interventions are methodologically fraught the lack of randomised controlled trials should not prevent addressing the health of patients with psychiatric disorders holistically. At the very least it will help address the significant physical comorbidity such as metabolic syndrome and has every chance of improving outcomes for their mental health. Moving beyond the individual patient, it is considered that the food industry is at an equivalent point to the tobacco industry in the 50’s and further scrutiny and regulation, along with raised consumer consciousness has the potential to deliver a cost effective and efficacious mental health intervention at the population level.
“...it is considered that the food industry is at an equivalent point to the tobacco industry in the 50’s...”
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Dr Clayton Smith
Dr Clayton Smith FRANZCP is a psychiatrist in private practice in Burwood, Sydney and also provides consultancy and supervision at The Mindspot Clinic, an internet delivered Cognitive Behaviour Therapy treatment program. He has a particular interest in the management of anxiety disorders and behavioural therapy, in particular, Acceptance and Commitment Therapy.
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