Major changes in public health policy similar to those seen for cigarette smoking and alcohol consumption are required for the public to make the connection between nutrition and brain health and alter their diet to improve mental health, urged a panel of experts.
The topic of nutrition and mental health was debated on 29th June by leading experts as part of Food for Thought 2020: The science and politics of nutrition, hosted by the Swiss Re Institute in partnership with The BMJ and held virtually due to the coronavirus pandemic.
It highlighted how, although there is a growing body of evidence to support the connection between dietary patterns and mental health, as well as the possibility of reducing symptoms in those with mental illnesses such as depression, this has not filtered through to public consciousness.
The debate, which was chaired by Dr Chris van Tulleken, infectious diseases doctor at University College Hospital London, and a BBC science presenter, was well received online.
Lisa Lovell, an NHS dietitian from Reading, took to Twitter to describe the discussion as "very interesting" and "very balanced".
Susan Dopart, a nurse and certified diabetes educator in Santa Monica, California, said it was "illuminating and informative", and underlined how the Western diet is "not working".
The debate was opened by Felice Jacka, professor of nutritional psychiatry and director of the Food & Mood Centre at Deakin University, Melbourne, Australia.
She noted that unhealthy diet is the leading cause of illness and early death across the world, and the costs to health and the environment of industrialised food systems are "now about $12 trillion per year", and expected to reach $16 trillion by 2050, "which is equivalent to the GDP of the whole of China".
This, she says, is "incredibly unsustainable and causes a huge amount of illness via chronic disease".
Alongside that, mental health disorders, particularly depression, are the leading cause of disability worldwide, and "the fact that these two things are linked then gives us opportunities for prevention and new opportunities for treatment", which has "some large public health implications".
Prof Jacka said that it’s been 10 years since the first studies linked diet quality and mental health, and there is now a "very large and fairly consistent" evidence base across age, geographic and cultural distributions, showing that dietary quality is linked to particularly depression, largely independent of other factors.
Animal studies have also demonstrated the direct impact of food on the brain and behaviour, and emerging research from clinical trials suggests that helping people to improve their diet can have a "substantial impact" on mental health, including depressive symptoms.
Moreover, improving dietary quality has benefits on the comorbid physical diseases commonly experienced by individuals with mental illness, "so there’s a double benefit".
She said that her SMILES trial and other studies have shown that "if you help people to improve their diet a) they can do it, b) they experience a pretty good benefit to their mental health, and c) the degree of their dietary change correlates pretty closely with the degree of their improvement in their mental health symptoms".
"It’s highly cost effective to do this" and consequently it’s a "win-win" Prof Jacka said.
Ongoing studies are looking at what underlies this effect, "with a particular focus on the gut microbiome, but also direct impacts on brain plasticity, immune system stress responses, etcetera" but, for her, the "target" of a lot of their efforts is public policy as well as clinical services.
Next, Dr Joseph Firth, presidential fellow, division of psychology and mental health, University of Manchester, referred to a paper accompanying the debate that was published by The BMJ.
He said that the relationship between nutrients and mental health is "of course, bidirectional", with the "obvious example" being how an individual with low mood is more likely to eat unhealthy food as so-called comfort foods.
In addition, mental illness is linked to a "broad range of environmental and socioeconomic circumstances that can limit people’s ability to maintain a healthy diet".
The medications used to treat mental health conditions may also have adverse effects that interfere with an individual’s appetite and other health behaviours.
More recently, there is emerging evidence on how diet and particular foods can affect mental health, both broadly and specifically in relation to mood, with certain neurobiological pathways having been put forward, such as high sugar intake potentially affecting brain function via inflammatory pathways.
Dr Firth said there are some "central messages, which apply across the board when we’re thinking about diet and mental health", such as how diet can affect cardiometabolic health, and that "of course metabolic and cardiovascular diseases themselves are associated with mental illness".
Again, that is bidirectional.
"It stands to reason that providing people with effective interventions or public health initiatives or environments that can promote healthy eating and good diet could be one piece of the very complicated puzzle around preventing physical and mental comorbidities, or at least hopefully trying to reduce the very high prevalence and long-term burden which we see from physical or mental comorbidities in modern society."
'Brain Healthy Diet'
Dr Georgia Ede, nutritional psychiatrist, consultant, writer and speaker, spoke next, suggesting that people are "confused about what constitutes a brain healthy diet".
While there is "broad consensus" over the notion that the Western diet is unhealthy, she said, there is "less consensus about what makes it unhealthy".
For her, the key elements are refined carbohydrates and industrial oils, "which set the stage for chronic inflammation, oxidative stress and insulin resistance".
"These are common underlying features of most neuropsychiatric conditions," she said, "so if we want to try to turn the tide on our global mental health crisis, this way of eating clearly must change, we all agree."
However, there is a lack of clinical information as to what form those changes should take.
Dr Ede said that, based on our current knowledge, prevention should centre on feeding the brain with the foods that are known to help it "function properly...over the lifespan", while excluding foods that promote inflammation or oxidation, or interfere with nutrient absorption.
She highlighted, for example, that unsupplemented vegan diets lack vitamin B12 and "cannot meet the brain’s requirement for DHA [docosahexaenoic acid, an omega-3 fatty acid], particularly during early growth and development".
In contrast, the Mediterranean diet encourages the consumption of whole plant and animal foods, includes healthy fats, and discourages "junk foods".
It nevertheless "sanctions use of up to 2 glasses of red wine per day, which is an addictive neurotoxin that promotes oxidative stress", as well as allowing the consumption of "nutrient poor grains and legumes".
Dr Ede instead recommends in her practice a "pre-agricultural" diet consisting of whole plant and animal foods, but with no grains and legumes, and "careful supplementation" for those who do not wish to eat animals.
If that does not relieve symptoms, she suggests a "metabolic evaluation" to look for nutrient deficiencies, inflammation markers and indicators of insulin resistance, which is "just as bad for the brain as for the body", and for which she recommends a low carbohydrate, whole foods diet.
Moving on to ketogenic diets, which Dr Ede described as "powerful biochemical interventions", she said they can "stop seizures in their tracks" in individuals with epilepsy, "and therefore have profoundly stabilising effects on brain chemistry".
She has also seen individuals with "crippling anxiety" feel "at peace" on ketogenic diets, while those with ADHD are able to "focus without stimulants" and people with early Alzheimer’s have gained "improved mental clarity".
However, she said that "no diet, including the ketogenic diet, is right for everyone or works for everyone", adding that her hope is "simply that the nutrition hypotheses we test and recommend be rooted in brain biology rather dietary ideology".
Finally, Kimberley Wilson, chartered psychologist, author and visiting lecturer, and governor of the Tavistock & Portman NHS Mental Health Trust, said that, unlike for physical health, "there isn’t a consistent, integrated public health campaign for the brain", comparable with smoking cessation, alcohol moderation or other lifestyle interventions.
She said that: "If you stop the average person on the street, they can tell you two or three things they can do to take care of their physical health but they have no idea how to look after the most complex and important organ in their body."
Consequently, she believes that "there is a real gap in the public’s knowledge of the research and how to implement that research in practical ways".
It is also important to understand that psychologists are not trained in the fundamentals of brain health and how nutrition is important for maintaining brain health in normal circumstances, not to mention during illness.
She said that: "Mental health is the only sphere of health where, rather than think about the principles of prevention, we wait for something to go wrong first.
"We wait for the anxiety attack, the panic attack, the depression, maybe the psychotic break, and then move to treatment.
"What we’re not doing is using the principles of prevention in the same way that we would asking people to reduce the intake of cigarettes to prevent lung disease."
Ms Wilson underlined that "we can help people be informed in order to apply the principles of prevention... to help risk reduction in the realm of mental health, and I think that’s something we should really focus on as a profession".
Adolescent Mental Health
In the subsequent debate, the importance of nutrition in childhood and adolescent mental health was discussed, with Prof Jacka noting that a range of research has shown that dietary quality in early life is strongly linked to outcomes, although there are, as yet, no related interventions.
Ms Wilson emphasised that there is emerging research not only on micronutrients but also the "impact of hunger itself on children’s brain development and behavioural functioning, and that’s been a big issue in the UK".
She continued: "What we know is that children who are hungry find it very difficult to concentrate but are also much more impaired in impulse control and they feel more aggressive." This can be demonstrated with a higher expression of cortisol, which is seen as agitation.
"Even when you control for other features of deprivation, children on free school meals are four times more likely to be excluded because of their behaviour, and so we’re thinking about the long-term implications of hunger on behaviour, on exclusion, and then potentially on those children’s life chances."
There was also consensus on whether sugar addiction should be included in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), with the panel agreeing that sugar does not meet the criteria for addiction in humans.
Professor Jacka said that she is "always very concerned when a particular macro- or micronutrient is demonised, because it’s just not supported by evidence".
Ms Wilson noted that, as well as the nutritional aspect, we have an "emotional relationship with food", which is "more than the nutrients on the plate". It's also about "our culture, our history, our family history" and religious festivals, with the result that "we use food in lots of non-nutritive ways" that may be associated with comfort or relaxation.
It is therefore more useful to "think about the underlying emotional needs" related to sugar intake, rather than just to look at the nutrient itself.
To close, the panel were asked about the one policy change they would like to see implemented or the research question they would like to see answered.
Dr Firth called for restrictions on advertising around fast foods, as has been seen for cigarettes and alcohol, particularly for adverts that target low mood, while Professor Jacka suggested that ultra-processed foods be made more expensive and "harder to get", rather than being available in every shop and on every counter.
Ms Wilson said she would like to see a "cross party agreement that children shouldn’t go hungry, that we need to focus on maternal and early years nutrition", because the foundations of a "healthy brain, of good brain development, of pro-social behaviour, of good mental health are laid in childhood".
Dr Ede noted that the United States dietary guidelines, which "set the tone for most dietary guidelines around the world... explicitly recommend the consumption of refined carbohydrates as part of every dietary pattern they sanction," as they recommend that half of all grains are whole, and "what that actually means is you’re making half of all your grains refined".
She said that the guidelines consequently need to be cleaned up, as the guidelines influence how hospitals, nursing homes and prisons feed people, "and we need to at least get the junk out of our explicit dietary recommendations".
Open access fees for the paper were funded by Swiss Re.
Stephen C. Cunnane, an author on The BMJ paper, was supported by the Alzheimer Association (USA), Canadian Institutes of Health Research, Fonds de la recherche en santé du Québec, Natural Sciences and Engineering Research Council of Canada, and Nestlé Health Sciences; has done consulting for, and received honorariums, test products, or research funding from Abitec, Nestlé Health Sciences, Cerecin, and Bulletproof, and is the founder of Senotec
No other conflicts of interest declared.
Food for Thought 2020: Food for mind and body: The impact of nutrition on mental well-being. Presented June 30th.