Mental Health and Your Diet
About 10 years ago, modern research started looking at how our diets could be effecting our mental health. When looking at depression, it seems like the least obvious place to start - looking at our gut and what we put into it. However, studies now show that the way we feel mentally may be significantly effected by the foods we put in our bodies.
It was George Porter Philips who, in the 20th century, decided to look into this after walking the wards of London’s notorious Bethlem Royal Hospital. He noticed that his patients with melancholia often suffered from severe constipation, along with other signs of a “general clogging of the metabolic processes” – including brittle nails, lustreless hair and a sallow complexion.
It was a natural assumption that the depression had led to the physical problems, but Phillips wondered if, in fact, the connection might not be the other way round. By targeting the gut, could you ease the melancholia?
Mental Health and Diet Studies
And so the studies began. To find out if his hunch was right, Philips began feeding his patients on a mostly plant based diet, devoid of meat, but allowing fish and instead of giving regular milk, he offered them a fermented milk drink known as kefir, which contains the lactobacillus bacteria, a “friendly” microbe that was already known to ease digestion.
Remarkably, it seemed to work. Of the 18 patients Phillips tested, 11 were cured completely, with two others showing significant improvement – offering some of the first evidence that our gut bacteria can have a profound influence over our mental wellbeing.
Despite early studies (including Philips’), the idea that the gut had any affect on our mental health was not well received. However, there is now a strong evidence base to suggest otherwise and the following summary of some interesting modern research is based on an article from the BBC’s website
‘One of the most striking modern experiments came from Kyushu University in Japan in 2004. The team first demonstrated that “germfree” mice – raised in sterilised conditions so they have no microbes on or in their bodies – showed greater fluctuations in the hormones corticosterone and ACTH, both of which are known to reflect stress levels. This suggested that the gut bacteria of healthy mice were somehow shaping their hormonal profile.
The researchers then dosed a group of germfree mice with lactobacillus bacteria – the class of ‘friendly’ bacteria that Phillips had also used on his melancholic patients. Although these mice still showed a higher stress response than the mice that had not been raised germ-free, their stress responses were less pronounced than the mice without any gut microbes.
There are even some signs that depressive behaviours can be transmitted across species – from human to mouse – through the microbes in the gut. In one study, Chinese researchers in Chongqing took a sample of the gut microbiota from patients with Major Depressive Disorder and planted them in germfree mice. These mice subsequently were quicker to quit, on a "forced" swimming task – a behaviour that is often considered to be analogous to the lethargy and hopelessness found in depression. And when the mice were placed in a box, they spent less time exploring the central areas and instead stayed closer to the edge, where they felt more secure.
“What was remarkable was that the animals that receive the ‘depressed’ microbiome, behave depressed,” says Julio Licinio at New York Upstate Medical University, who was a co-author on the paper. “If you change the microbiome, you change the behaviour.”
We can only draw so many conclusions from these animal studies, of course – but their conclusions are supported by epidemiological studies examining vast numbers of human participants (the most recent was published on 4 February 2019.) These studies have consistently shown that differences in the gut microbiota coincide with various mental illnesses, include depression and anxiety.’
It it quite usual nowadays to suggest to clients with mental health problems, particularly depression, that they should switch to a healthier diet. Maybe the current research will lead us to advising a change to a diet that creates a “healthy gut biome”. One difficulty with this approach is that we all have a unique biome, with no more than a 10% overlap between any two individuals so, ideally, the advice would need to be very specific to the individual. However, work is underway to create “categories” with sufficient commonality to enable an effective recommendation for everyone in that category. If this seems like an expensive approach it is, in my view, well worth it. Anxiety and depression are of epidemic proportions in the developed world so the economic effects (cost of mental and physical treatment, lost working days etc.) merit the research costs. For me however, the primary reason is to help the millions of people who are living a joyless life, with mental health problems that are causing physical damage and, potentially, early death.