The Mind-Gut Connection: Depression Linked to Gut Bacteria and What We Eat?

Battling with depression? It may not be in your head but in your gut instead. In recently published studies, Flemish researchers linked our gut biomes to mental health, in particular depression. Individuals with depression, whether or not they were on antidepressants, consistently had depleted levels of two gut bacteria – Coprococcus and Dialister. For years now, researchers have seen growing evidence that our gut biomes greatly influence not just our digestive and metabolic health but also our moods. The takeaway? How our gut bugs are doing will impact how we’re doing. And what we feed ourselves – and them – matters. Here’s why.

Bugging Out

We all carry zillions of bacteria on and in our bodies. The gut microbiome consists of tens of trillions of microorganisms, including at least 1,000 bacterial species, and can weigh up to 2 kg. While around one-third of gut microbiota is common to the majority of people, around two-thirds are specific to each individual. As such, researchers are interested in how the gut microbiome may impact human health.

Many types of gut bacteria are helpful. Most we receive at birth from our mother and from breast milk. These help inoculate us against infections and help our immune systems develop but also help prevent diseases and autoimmune disorders. We gain bacteria too from the foods we eat and our everyday interactions with our environment. We need these bacteria and others we acquire growing up. They produce anything from enzymes to help digest our food to neuroactive compounds that impact our moods. Specifically, these microbes aid digestion, as well as the production of vitamins, hormones, and essential amino acids.

The Flemish study is the latest of studies done with humans rather than with animals. The Flemish researchers, in addition to linking gut bacteria species and their levels with depression, have previously found low bacterial counts and biodiversity among Crohn’s disease patients as well as those with intestinal inflammation and reduced wellbeing. They all share sets of common microbial features.

The relationship between our gut microbiome and mental health remains a controversial topic in microbiome research despite years of mounting evidence, research and clinical studies that all point to a very direct connection. It’s almost as if the notion that bacteria in our guts can interact with our brains is too much for scientists to accept despite the body of evidence. After all, who wants to think that we aren’t in complete control of our emotions and moods – or even our thoughts? That goes against our well-loved beliefs in complete self-agency and free will. Scientists don’t like to accept, other than abstractly, that we are a complex biome with many moving parts – and tiny creatures – making us up.

But that symbiosis is real and it has consequences. Researchers have looked for years now at the relationship between food and the health of our gut bacteria and have found links between allergic diseases that develop during childhood, such as eczema, asthma, and allergies to low bacterial diversity. Other studies have linked gluten and unbalanced gut bacteria levels with diseases like celiac disease and even autism. These latest studies on various diseases and mental health are pieces of an evolving and complex picture.

Cause and Correlation

Depression can happen for a number of reasons but it’s interesting to see that in a study of clinically depressed patients, they had the same low levels of those two bacteria mentioned before when compared to non-depressed individuals.

How can gut flora interact with our brain? As the Flemish scientists noticed, some make neuroactive compounds. There are other ways for bacteria to interact with our minds. Stress is known to increase the permeability of the intestinal lining which gives bacteria easier access to both the immune system and the neuronal cells of the nervous system but evidence exists that bacteria in the intestines can activate stress circuits by directly activating the vagus nerve – a cranial nerve supplying a number of organs, including the upper digestive tract.

A more direct route still might involve direct contact of the microbiome with the sensory neurons of the nervous system. Studies have shown that these sensory neurons are less active in germ-free mice, and, once the mice have been given probiotics to restock their microbiome, the activity levels of the neurons return to normal.

Symbiosis With Ourselves

Our gut biomes are important to our overall health and mental health. Unfortunately, we actively destroy our gut biomes rather than live in symbiosis with them. This has consequences on our health and, as we are increasingly realizing, on our mental health as well. Here are the many ways we go to war on ourselves.

Antibacterial Warfare. We pop antibiotics like candy, give them to livestock, and put antibacterial chemicals in our water, soaps, and everyday household cleaners – just to name a few. Hand sanitizer is everywhere – even when you walk into grocery stores and places like Wal-Mart. While obviously we want to prevent bacteria-born illnesses and cure life-threatening infections, most of these products don’t differentiate between good bugs that keep us healthy and those that are hurting us. This overuse has for years now drawn global alarm from doctors and non-governmental agencies, particularly since it’s causes drug-resistent superbugs.

Food Poisoning. The second major way we actively damage our health is through the food we eat. Diet is a major player in determining which microbes take up residence in our guts long-term. A Western diet, high in fat and refined sugars but low in fiber, is thought to reduce microbial diversity. Salt and sugar are known antibacterial agents – that’s why we use them so much as preservatives in food products and processed food. Preservatives mostly fight bacteria that would otherwise make our food mold or get contaminated by harmful bugs that could make us sick. But when we eat these high sugar and high salt foods, we are also killing off our good gut bacteria during the digestive process.

Playing Favorites. In a similar vein, foods can impact our ecosystems by unbalancing the various bacterial species we carry. Foods, like wheat, have been shown to correlate with gut biome compositional changes, as have even dark chocolate and beer. What we eat matters. Foods basically feed and encourage certain species to flourish while causing others to die off. After all, bacteria are living organisms. They need food to survive. Over the past century our eating habits have changed drastically from whole foods based to highly processed. The good gut bugs that we evolved with prefer the whole foods – the fruits, vegetables, beans, nuts, seeds and some types of whole grains. They die in the face of processed and wheat-heavy foods like pasta, pizza and our sugary treats and salt-loaded meals and snacks. When these good organisms die, we lose the benefits of their health boosting or health maintaining processes. Even worse, this poor diet can actually feed harmful bacteria! For good health, we should be feeding our good bacteria what they need – not what the harmful bacteria need.

Over-medicated. Studies have also found a link between medication use and gut microbiota composition. use of laxatives, antibiotics, hay fever medication, and hormones used for birth control or menopause symptoms were found to affect gut microbiota diversity.

Gut Feelings

A few years ago I started reading books like Wheat Belly and Grain Brain, which link our eating habits to a variety of illnesses and autoimmune disorders – particularly wheat. When I gave up wheat, many of my illnesses like chronic pain, high blood pressure and others began to fade until now, they only reappear when I eat wheat-based foods like pizza, pasta and bread. I don’t even get colds anymore. Read my article What Happened When I Gave Up Bread. More startling, my moods began to even out as I switched from processed and wheat-filled foods to a whole foods diet.

While I use meditation and mindfulness to combat my own long history with depression, my eating habits are a major component of my mental health care regimen. It’s not just to control my weight or prevent diabetes. Food impacts us in so many ways. Eat sugar and wait for the rush from the blood sugar spike – and maybe reactions from your gut bugs too. Any kid on sugar looks like an insane little monster. How can we say food doesn’t impact mood and behavior?

Studies discuss anxiety in people who regularly eat sugary foods and wheat, which breaks down so quickly it hits our systems like sugar. These foods also destabilize and destroy our helpful gut biome levels. Without them to produce their enzymes and neuroactive compounds, we face disorders in our metabolism that can surface in our moods and our immune system, just for starters. After all, we are chemical beings and food and drink are our primary ways of obtaining the chemicals we need to function well and maintain ourselves.

These impacts can be reversed in some circumstances. Changes in diet to include more fiber have helped individuals whose biome was negatively impacted by the low-fiber Western diet. Probiotic studies in humans and animals showed that probiotic use also brought significant and helpful changes to patient microbiomes. Over 2-4 weeks, probiotics showed efficacy in improving psychiatric disorder-related behaviors including anxiety, depression, autism spectrum disorder, obsessive-compulsive disorder, and memory abilities.

Strengthening Our Mental Health

The Western diet of processed food, refined carbs and sugar, low fiber and high salt are all linked to diabetes, cancer, stroke, kidney disease and a host of other problems. Can we really think this way of eating won’t also impact our mental health?

Scientists are actively trying to catalogue the species of gut bacteria that could potentially interact with the human nervous system. So far, they’ve identified over 500. The takeaway is that perhaps good mental health is as close as changing our diets to help grow our healthy gut biome so that it can produce the enzymes, vitamins and hormones we need for a healthy mind and more stable moods.

As complex as depression can be, food and probiotics are probably not the be all end all answer. Good health, though, is the first line of defense against susceptibility to most illnesses so we can only gain from a good diet. Looking to our diet is also a good starting place and something we can do immediately to take back control from our depression. After all, food has long been called medicine. Look into a whole foods diet today. Hopefully it can help you as much as it has helped me and so many others.

Like this article? Please share it so that others can learn these health secrets and start living their best lives now.

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