FEED YOUR MIND
Could scientists have found the mental health diet?
Your attention was probably elsewhere in the late 90s. Repeat viewing the music video for Wannabe to decide which Spice Girl you were most like – or trying to work out if Leonardo Dicaprio and Kate Winslet could both have fitted on that floating door, perhaps. Regardless, you may have been too preoccupied to have spotted a study published in The New England Journal Of Medicine in 1997 about how a specific way of eating can significantly influence blood pressure. The dietary approaches to stop hypertension (DASH, to its friends) diet was found to substantially reduce hypertension (hence the name), thanks to the reduced fat consumption that came with a diet rich in whole grains, fruit, vegetables and low-fat dairy. Cool story for anyone looking to reduce their blood pressure stats. But also relevant for pretty much everyone else, because – so says a growing body of research – this niche 90s diet could be the key to future-proofing your mind.
Last April, more than two decades after DASH was first conceived, a study presented to the American Academy of Neurology found that those who followed the DASH diet, or something similar, were less likely to develop depression than those who didn’t. Conversely, those same researchers from Rush University Medical Center in Chicago found that the more closely participants followed a typical Western diet (high in saturated fat and red meat, low in fruit and veg), the more likely they were to develop depression. ‘This is a relatively small study that was observational in nature, so we can’t claim a cause-and-effect relationship,’ says Dr Laurel Cherian, assistant professor in the Department of Neurological Sciences at Rush and lead author of the study. ‘But I think the results are one more piece in a larger puzzle that is coming together to show us that diet is a valuable weapon in our arsenal against depression.’
EATING YOUR FEELINGS
Dr Cherian’s not wrong. Other pertinent pieces of the puzzle include a 2017 study in which Spanish researchers found that those who followed the DASH diet, even moderately, had a lower risk of developing depression. Australian researchers have also found that a diet centred around fruit, vegetables, fish and whole grains – DASH by any other name – was associated with lower odds of developing major depression and anxiety disorders, while a Western diet was associated with higher odds. Particularly significant was the fact that this research didn’t just look at the benefits of DASH in older people – as in the Rush study – but included women as young as 20.
The notion that what you eat affects your mental health is by no means new. But while you might have long suspected that this relationship exists, it’s only relatively recently that experts have been able to say why. ‘Nutritional psychiatry is an exciting and promising area of research, with important implications for how we assess and treat depression and other mental
health problems,’ explains Kimberley Wilson, whose London practice, Monumental Health, combines the latest research into nutrition neuroscience with psychological therapy.
Some scientists are staking their careers and reputations on the notion that what you eat is intrinsic to how you feel, but – as with Melania and Donald – understanding why this relationship exists is a tricky one. ‘Proving a direct causal relationship between health and food is enormously complicated because there are so many variables that can affect outcomes,’ adds Wilson. ‘Add mental health into the mix and you’re introducing another layer of complexity given that, historically, mental health research hasn’t had the same funding as, say, heart disease or cancer.’ But, she explains, there are two key strands that researchers are exploring: the ways in which following a good diet can help future-proof your mental health, and how and why a bad diet can have a negative impact on your mind.
INFLAMMATORY RESPONSE
Recent research indicates that it’s what you don’t eat on the DASH diet that could be key to understanding this protective effect. It can be explained in a word that seems to have captured the imagination of the scientific community the way inflatable pool toys have for Instagrammers this summer: inflammation. In the past decade, scientists have started looking into the potential links between inflammation and depression – specifically, the idea that reducing the former could protect against the latter. In a 2016 study*, researchers concluded that a better understanding of inflammation in the brain could help treat depression more effectively, and earlier this year, a Cambridge professor dedicated an entire book to the subject. In The Inflamed Mind (£14.99, Short Books), Professor Edward Bullmore, head of psychiatry at Cambridge University, investigates the growing body of evidence that links eating high-fat foods with inflammation, which, in turn, can contribute to depression. ‘There are many inflammatory cells embedded in fatty adipose tissue, which is why obesity is associated with an increase in blood levels of inflammatory proteins, such as cytokines,’ he explains. Cytokines are proteins that play an important role in the way our cells communicate with each other. ‘The evidence shows that increased cytokine levels can cause inflammation in the brain, leading to withdrawal from social contact, loss of pleasure and other depressive symptoms.’ The fact that an association has been found between obesity and inflammation, Professor Bullmore explains, could help to explain why there is also an association between obesity and depression. But as to the question of whether an antiinflammatory diet can protect against depression, he is clear: we need a great deal more evidence before we can make any conclusions. ‘I think it’s conceivable, based on my work, that changing your diet could have an anti-inflammatory effect – and therefore could offer mental health benefits – but we need much more data to be sure.’
GUT INSTINCT
The absence of high-fat foods only goes some way towards explaining why DASH could be so effective. Factor in the protective effect of many of the foods that the DASH diet advocates, and the case for keeping your mind healthy via your plate stacks up. This is where the mind-gut connection comes in. Prebiotic plants, the likes of asparagus, leeks and Jerusalem artichokes, feed your gut microbiome as effectively as a Mcmuffin feeds a hangover.
‘Prebiotics are dietary fibres found in plants that the good bacteria in your gut feed on to multiply,’ explains Dr Philip Burnet, associate professor in the Department of Psychiatry at the University of Oxford. ‘Gut bacteria contain an amino acid that affects a certain type of molecule in the brain,’ he adds. ‘I wanted to see if increasing beneficial gut bacteria with a prebiotic supplement – and in turn producing more of this amino acid – could improve mood and cognitive processing. It turns out it does in animals, and to some extent in humans, but this isn’t happening via the amino acid that we thought. We now think it happens via the immune system, and the molecules produced from the bacterial digestion of
‘Diet is a valuable weapon in our arsenal against depression’
the prebiotic.’ Once again, more human studies are needed, but Dr Burnet believes that prebiotic supplements could work via the same mechanism as anti-depressants, by reducing levels of stress hormones in the brain.
So what about prebiotic plants, the likes of which you find on your average DASH plate? ‘Plants contain carbohydrates, which have prebiotic properties, meaning they should provide the same health benefits via the gut bacteria,’ adds Dr Burnet. ‘But all natural prebiotics and supplement formations still need to go through clinical trials to test if they really do have therapeutic effects on mental illnesses. So far, we have only shown that a prebiotic supplement influenced one psychological pathway that underlies mood – we didn’t see a change in mood per se, and we won’t know more until more work is done.’
ANTI-DIET
If it’s a case compelling enough to give you yet another reason to take up a veg-box subscription, it can have more problematic implications for those for whom mental health is an ongoing battle. It’s important to consider the evidence in context, adds Dr Cherian. ‘When we talk about the role that diet plays in mental health, it isn’t a case of telling people “eat this and you’ll feel better” or “eat this and you won’t get depression” because it certainly isn’t that simple,’ she explains. ‘But changing your diet in a way that reduces your consumption of high-fat food and increases your intake of prebiotic plants could play a crucial part of a comprehensive plan for preventing, and also treating, depression – comprehensive being the important word. Medication, therapy and exercise all play an important role. It’s my view that those who combine all of these with good nutrition may see the greatest benefit to their mental health.’
Where this diet has real promise, adds Wilson, is that it isn’t a diet as you might understand the term – there’s no calorie counting, nor a list of foods never to be touched again. ‘DASH is a combination diet, meaning it encourages people to eat well without limiting what they allow themselves,’ she explains. ‘Like the Mediterranean way of eating, DASH is neither restrictive nor prescriptive. Because it provides guidelines for people to work within and adjust to suit their lifestyle, there’s no falling off the wagon or messing up.’ In short, it’s a diet in the truest sense of the word; a selection of foods rather than a regime. One that doesn’t make you feel shit about yourself for tucking into a colleague’s birthday cake – one that recognises you’re human. That’s some smarts.