Published 14th December 2021

Does gut health affect mental health and can diet help?

Your gut health and your mental health both have an important impact on your overall well-being — but are the two linked? Research suggests they are and that gut health may even affect specific mental health conditions like anxiety and depression. 

However, it’s a relatively new area of research, and there’s still a lot we don’t know. What scientists can say is that your brain and your gut are connected in a number of ways and that your gut microbiome plays a key role in this. 

Your gut microbiome is the collective name for the trillions of bacteria and other microbes that live in your gut and impact the way your body functions. Because your diet influences your gut microbiome, it’s also possible that what you eat can affect your mental health.

ZOE’s at-home test can tell you lots about the health of your individual gut microbiome, including how many of the 15 “good” and 15 “bad” gut bugs that we’ve identified live there.

To find out more about your personal gut health and what you can do to improve it, read more about the ZOE program.

The gut-brain connection and mental health

If you’ve ever found yourself suddenly desperate to go to the bathroom before an important interview, or while you’re waiting in line for a rollercoaster, you may not be surprised to hear that there’s a direct connection between your gut and your brain.

What you might not know is that there are actually several routes through which this two-way connection lets your gut and your brain communicate, and that your gut microbiome is a key player in all of them. 

But how can a collection of bacteria influence how you think and feel? Scientists have identified three key pathways that make up the gut-brain connection:

  • Vagus nerve pathway: Your gut has its own large and complex collections of nerve cells called the enteric nervous system (ENS), sometimes known as the “second brain.” Your gut microbiome affects how your ENS links to the large nerve called the vagus nerve, which runs directly between your gut and your brain.

  • Immunoregulatory pathway: Specific gut microbes may influence the functioning of cells in your immune system, including those in your brain. Changes to the balance of your microbiome may lead to unwanted inflammation that has been linked to mood and depression. 

  • Neuroendocrine pathway: Your gut bugs can affect the production of substances such as tryptophan, an amino acid that is an important building block for neurotransmitters like serotonin that influence mood.

Gut health, anxiety, and depression

According to large-scale studies, over a third of people have experienced anxiety at some point in their lives. 

Anxiety can be short-term and connected to a specific situation like a stressful event. As we’ve mentioned, this can lead to the kind of sudden gut problems that many people will recognize.

But for some people, like those with generalized anxiety disorder (GAD), symptoms can carry on for long periods of time. If you have GAD, you may experience a continual sense of dread, or feel “on edge” or irritable, without knowing why. 

You might notice physical symptoms like heart palpitations, headaches, and sickness. And you may have ongoing gut problems like irritable bowel syndrome (IBS).

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Anxiety can be associated with depression, too. One worldwide survey found that almost 46% of people who had experienced depression also had a history of anxiety.

Scientists have looked at the relationship between the gut microbiome and mental health using a technique called fecal microbiota transplant (FMT), where samples of poop containing bacteria from one person’s microbiome are transplanted into another person. 

In eight different studies, researchers transplanted poop containing microbes from the guts of people without mental health conditions into those with combinations of anxiety, depression, IBS, and other conditions. 

In all studies, the symptoms of the people who received the samples were significantly reduced, although in most cases, improvements only lasted for a number of months.

Scientists have also found specific types of gut microbes that are linked with mental health.

In a study of over 1,000 people, two groups of bacteria called Faecalibacterium and Coprococcus were associated with improved mood, while Coprococcus and another group called Dialister were found to be less common in people with depression.

Can your diet affect your mental health?

There’s an increasing amount of evidence that the food you eat can have a significant impact on your mental health.

In particular, diets that contain lots of plants, healthy fats, and whole grains — rather than processed foods — have been linked to improvements in certain mental health conditions. 

One group of researchers examining the relationship between diet and mental health found that people who eat diets containing lots of fiber and omega-3-polyunsaturated fatty acids — found in foods like oily fish and seeds — seem to have less risk of developing symptoms of depression, anxiety, and stress.

People who eat a Mediterranean diet — full of fruits, vegetables, and wholegrains, and lower in red meat, processed grains, and fried foods — also tend to have a lower risk of depression, as well as a healthier gut microbiome.

Research from a clinical trial involving people with depression echoes these findings about “high-quality” diets.

After working with a dietitian to improve what they ate over a 12-week period, participants saw a significant reduction in their depressive symptoms compared with those who didn’t have sessions with a dietitian. 

Probiotic supplements

If you’re looking to improve your gut health, you may have thought about taking probiotic supplements. 

Probiotics are live microbes that scientists believe may provide health benefits if you consume them. But evidence that taking probiotic supplements can help with your mental health is patchy.

A recent review of 7 studies into the effects of probiotic supplements on symptoms of depression found positive benefits, but some of the studies were of poor quality. 

Researchers also recently looked at 21 studies that tested the effects of probiotics and other dietary changes on people with anxiety. Of 14 studies that used probiotics, 5 (36%) saw improvements in participants’ anxiety symptoms. 

But of seven studies using non-probiotic treatments, all but one was effective, a success rate of 86%. The collective data from these studies suggest that changing your diet might be more effective than taking supplements to improve anxiety symptoms.

One reason that the probiotic supplements were less successful than diet changes may have been the types of bacteria they contained. 

Firstly, different probiotics contain different strains of bacteria and many only contain a single bacterium, which is problematic since scientists believe diversity is important. 

And secondly, the probiotics that are currently on the market have been chosen not necessarily because they are the best for your gut but because they are the easiest to produce and package. 

Probiotic foods

At ZOE, we believe that probiotics can help to improve your gut health, but we look to foods that naturally contain a range of probiotics rather than the supplements that are currently available.

You can find probiotics in lots of different fermented foods. These include dairy products like yogurt, artisanal cheeses, and kefir, as well as fermented vegetables like kimchi and sauerkraut. 

To help encourage “good” bacteria in your gut to grow and thrive, you can feed them prebiotics, a type of dietary fiber.

Prebiotics are found in a wide range of vegetables, fruits, and grains, including asparagus, onions, leeks, garlic, bananas, Jerusalem artichokes, chicory root, legumes like chickpeas and lentils, barley, oats, rye, and other whole grains.

Eating fermented foods containing probiotics and healthy plants that help feed them is a good way for most people to improve their diets. At ZOE, we know that everyone’s gut microbiome is different and so are their personal responses to foods.

ZOE scientists have identified 15 “good” gut microbes that are linked to a number of different markers of better health and 15 “bad” bacteria linked to worse health. 

A ZOE at-home test can tell you which of these bugs currently live in your gut, as well as the entire range of bacteria that make up your gut microbiome. 

You’ll also learn which specific foods are your personal “gut boosters” and which are your “gut suppressors.”

The ZOE program can then help you to eat more of the foods that are good for your gut and less of those that aren’t.

Take a free quiz to find out how you can learn which foods are better for your body and your gut microbiome.

Summary

Your gut and your brain are connected, and an increasing amount of research suggests that your gut microbiome — the collection of bugs that live in your gut — plays an important role in this. 

Scientists are also starting to show links between the state of the gut microbiome and symptoms of mental health conditions like anxiety and depression.

When researchers transplanted samples of healthy people’s gut microbiomes into people with anxiety, depression, and other conditions linked to mental health, they found that the recipients’ symptoms improved.

Scientists have even identified specific types of bacteria that seem to be associated with mood and depression.

There’s also good evidence that diet plays a part in the risk of developing certain mental health conditions or how severe the symptoms are.

Diets that contain lots of plants, fiber, and healthy fats tend to reduce these risks and can improve the health of your gut microbiome.

Links between diet, gut health, and mental health have helped to make probiotic supplements popular.

However, research suggests they’re currently less effective than focusing on improvements to your overall diet, including eating the fermented foods that naturally contain probiotics.

To get the best results for your health, you should think beyond these general guidelines and start to look at the unique make-up of your gut microbiome and your personal responses to different foods. 

ZOE’s at-home test can tell you about the balance of “good” and “bad” bugs in your gut, and your personal “gut booster” and “gut suppressor” foods — and help you to rebalance your diet for your body.

Read about how the ZOE program works and what it can do for you.

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