“We are learning that the gut and its bugs are a key pathway by which diet can affect our health,” says Felice Jacka, Professor of Nutritional Psychiatry and Director of the Food & Mood Centre at Deakin University. “Diet is a very important driver of the health of our gut, and our gut, in turn, profoundly influences our immune system, our metabolism, the way our genes work, our stress systems, and the health of our brain. So, it’s critical that we feed it well.”
Founder and president of the International Society for Nutritional Psychiatry Research (ISNPR) and immediate past president of the Australian Alliance for the Prevention of Mental Disorders (APMD), Professor Jacka has led a highly innovative program of research that examines how diet interacts with the risk for mental health problems. Her current work focuses closely on the links between diet, gut health and mental and brain health; research that is being carried out with the ultimate goal of developing new, evidence-based prevention and treatment strategies for mental disorders. She recently published Brain Changer: The Good Mental Health Diet and her children’s book, There’s a Zoo in my Poo, was released in July 2020.
What inspired you to write There’s A Zoo In My Poo?
“We wrote ‘There’s a Zoo in My Poo’ in the hope that it might help children—and their parents and teachers—to improve the health of their diets.
We know that an unhealthy diet is now the leading cause of illness and early death across the globe, largely as a result of the industrialisation of the food industry—Big Food. The impact on young people has been huge; for example, 60% of children alive today in the US will be clinically obese by the time they’re 35. In Australia, less than half a per cent of young people consume the recommended intake of vegetables and legumes, while Australian teenagers eat an average of seven ‘extras’ foods a day (energy-dense, nutrient-poor foods such as margarine, sugar-sweetened soft drinks and chips). We now know that this type of eating can affect mental and brain health as well as physical health in the short and long term.
Our book is an attempt to give children the information and incentive to make healthier food choices.”
Why is it important to educate kids about the gut?
“Making good food choices for our gut doesn’t need to be complicated. We’ve given kids an easy-to-understand guide to how and why it’s important to feed our gut bugs well. We’ve also given some very simple and fun recipes for kids to learn themselves. Young people are capable of making good choices if they understand why—we’re hoping that they might even drive better food choices in their parents!”
Can you tell us about the benefits of fermented foods?
“Fermented foods have been part of traditional human diets for a very long time. It’s how we kept foods for long periods before we had fridges. To understand fermented foods, we need to understand what bacteria do to foods in our guts. The main job of our gut bacteria is to break down the parts of foods that our own body can’t do itself—this is mainly plant fibre and what are called ‘polyphenols’. Plant fibres are found in most fruit and vegetables, but also in other plant foods such as wholegrain cereals like rye, barley, brown rice and oats and legumes like lentils, chickpeas and beans. Polyphenols are chemical compounds found in many plants—a great number of them are powerful antioxidants with important health properties. When we eat whole plant foods, our human enzymes can’t break down the fibre and polyphenols, so they make their way to the gut where our bugs get to work. They break down these through a process of fermentation.
When these plant compounds are fermented by our gut microbiota, many different molecules are produced. These ‘fermentation products’ have a very wide range of health effects throughout our bodies. When we eat fermented foods, such as sauerkraut, kimchi, tempeh, kombucha, yoghurt and kefir, we are eating the fermentation products from the foods that the bacteria have already broken down. In other words, they can be short-cuts to getting the fermentation products. Many of these foods also have live bacteria in them, adding to our bacterial diversity. But even ‘dead’ bacteria seem to have actions within our bodies, so it might not matter if they’re alive or dead.”
What is the link between fermented foods, the gut and mental health?
“Some of the products created in the fermentation process include neurotransmitters; we don’t know yet if these directly affect our brain, but we do know that the bacteria in our guts affect the metabolism of tryptophan, which does affect the amount of serotonin in the brain. Importantly, fermentation products have an important influence on the immune system, and we know that the immune system is very much involved in mental health. There is some preliminary evidence that fermented foods can influence mental health directly, but we need to do more scientific studies to properly understand this. There is certainly evidence that taking probiotics may be helpful to depression and anxiety, but we really don’t know which species are best for this. I think that fermented foods are a better and safer bet than taking probiotics directly.”
If there was one thing everyone could do to support their gut health, what would you suggest?
“Try to eat a wide range of plant foods every day. These include fruit, vegetables, wholegrains, legumes and nuts and seeds. People who ate 30 or more different plant foods per week had a more diverse gut bacteria than those who ate ten or fewer per week, and we consistently see that more diverse guts are linked to better health.”