When it comes to diet, most people’s concerns involve weight loss, fitness, cardiac health and longevity. But according to Durban-born Dr Uma Naidoo, what we eat affects more than just our bodies. It also affects our brains and can have a profound impact on mental health.
Naidoo, who founded and directs the only American-based clinic in nutritional psychiatry, explores this link in her new book, The Food Mood Connection, an extract from which is published here.
“Many people focus on the way their diet affects their physical health, their figure, and the environment,” says Naidoo.
“But we don’t often think about our diet’s influence on our mental state, and the consequences of this blind spot are dire.
“Pre-Covid-19 statistics show that a staggering one in five American adults will suffer a diagnosable mental-health condition in any given year, and 46% of will meet the criteria for a diagnosable mental-health condition sometime in their life.
“In other words, there is an epidemic of poor mental health becoming more apparent in this country — one that could be mitigated more effectively, and even reversed, by simple changes to our diet and lifestyle.
“Now, more than ever, maintaining ourselves and our loved ones in optimal mental and physical health is key.”
In addition to sharing her thoughts on mental health and diet, Naidoo, the head of faculty at Harvard Medical School and director of Nutritional and Lifestyle Psychiatry at Massachusetts General Hospital, also shares a host of brain-healthy recipes with readers in her book.
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A trained chef, she believes that a sound diet can help treat and prevent a wide range of psychological and cognitive health issues, ranging from depression and anxiety to post-traumatic stress disorder (PTSD), obsessive compulsive disorder (OCD) and more.
Naidoo is not alone in her thinking.
In an article written and published on The Conversation online platform, Lynne A. Barker, an associate professor in cognitive neuroscience, and Caroline Jordan, a psychologist at the Centre for Behavioural Science and Applied Psychology at Sheffield Hallam University, said a healthy gut microbiome helps people to maintain overall wellbeing by ensuring that all necessary vitamins and minerals are absorbed from the food we eat.
When the gut microbiome’s balance becomes disrupted, through stress, illness or poor diet, however, it can result in digestion problems, and cause obesity, diabetes and brain disorders.
In their article, the two women say: “Our gut and brain are closely connected. They communicate with each other through the system known as the gut-brain (or brain-gut) axis.
“This axis influences the digestive system’s activity and plays a role in appetite and the type of food we prefer to eat.”
Stress signals from the brain can influence digestion through this axis, and the gut can also send signals that similarly influence the brain. Gut microbes appear to play a key role in sending and receiving these signals by making proteins that carry messages to the brain.
The microbiome can also influence brain activity through the vagus nerve, one of the brain’s 12 cranial nerve pairs. This nerve snakes through the body connecting internal organs to the brainstem at the base of the brain.
In this way, the vagus nerve provides a physical pathway between the gut and brain, enabling a different route for communication.
Through this connection, an unhealthy microbiome can transmit harmful pathogens and abnormal proteins to the brain, where they may spread.
When the microbiome becomes unbalanced, the first sign is usually digestive problems, or dysbiosis, with symptoms ranging from intestinal inflammation to a leaky gut (where the gut wall begins to weaken), constipation, diarrhoea, nausea, bloating and other gut-based metabolic changes.
Immune response and normal bodily functions in the liver, heart and kidneys may also be negatively affected.
Scientists have investigated the impact of dysbiosis on different neurological disorders, including Alzheimer’s, Huntington’s and Parkinson’s Disease, and multiple sclerosis, with early research finding a link between the two.
Barker and Jordan said research has shown that in patients with Parkinson’s Disease, constipation was common, while diarrhoea and constipation had been found in those with multiple sclerosis.
Other research found that patients with dementia-like conditions, including mild cognitive impairment and Alzheimer’s, are more likely to have dysbiosis compared to those without memory problems.
The initial cause of microbiome disruption in those with neurological conditions is not yet known, however.
On a positive note, the gut microbiome can be modified by choosing a diet rich in fibre, limiting stress, alcohol use and smoking, exercising daily and using a probiotic.
“As our knowledge increases, microbiome-targeted therapies might present a new way of treating or minimising diseases,” Barker and Jordan said.
“Probiotic use is a promising approach because there are few adverse effects, medications are likely to be better absorbed in a healthier gut environment, it’s less complicated than changing your diet, and is quick and easy to implement.
“It’s early days, and there is still much to learn, but based on current research it appears that gut microbiome health is more intimately tied to our brain health than we imagine.”