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Paul Bertrand, RMIT University and Trisha Jenkins, RMIT University

Your thoughts, moods and behaviours are the product of your brain – an exquisite spider’s web of neuronal connections and witch’s brew of neurochemicals.

It is this brew that is prone to change, and when “unbalanced” can cause dramatically altered behaviour. And your diet may have more to do with how you think than you would first suspect.

How your mood is made up.

Your mood is the product of chemicals in the brain called “neurochemicals”. This includes “neurotransmitters”, which are small molecules nerve cells (neurons) use to communicate with each other. One important neurotransmitter involved in mood is serotonin.

Many drugs that target the brain’s systems are designed to increase or decrease the levels of neurotransmitters. For example, many antidepressant medications such as fluoxetine or escitalopram are designed to block the disposal of serotonin and consequently increase its levels in the brain.

Watch: A simple, delicious green smoothie recipe. (Post continues after video.)  

What is serotonin?

Serotonin is popularly known as one of the happy hormones. It is produced by neurons in the brainstem.

However, these neurons connect with virtually every other major area of the brain, so serotonin’s effects are widespread. Serotonin influences many behaviours, including mood (such as happiness and depression), social behaviour, appetite, sleep, memory, and sexual desire – to name a few.

Serotonin is made from tryptophan, an essential amino acid. This means the body can’t produce tryptophan and we have to get it from the food we eat. Luckily, tryptophan is found in many foods such as meats, dairy, fruits and seeds.

But this raises an important question – if the amount of tryptophan in your diet changes, does the amount of serotonin in the brain change?

You are what you eat.

You might think the brain is pretty capable of managing its resources; that daily changes in diet would not affect your basic neurotransmitter make-up. It turns out this is true for a tryptophan-loaded diet, which is unlikely to increase levels of serotonin in the brain.

Under normal conditions, excess tryptophan competes with other amino acids to enter the brain. This results in very little extra getting through.

However, the opposite is not true. The brain cannot cope with a tryptophan-free diet, and this will quickly deplete the brain of serotonin. (Post continues after gallery.)

10 foods you never knew were healthy

Bread

KATIE THOMSITT, Dieticians Australia spokesperson says: "Lots of people shy away from bread to achieve weight loss. But bread is such an important source of fibre, and plays such a helpful role in weight loss and preventing bowel cancer. A couple of slices of a dark, seedy bread per day is absolutely fine."

Cheese

KATIE SAYS: "Cheese is definitely a higher fat source of dairy, but still a good dairy fat. Choose low-fat options if you have it regularly, otherwise consume it in moderation. One serve of dairy is 30g, so a couple of slices is absolutely fine."

Chocolate

KARA LANDAU, The Travelling Dietician says: "Studies have been able to show that dark chocolate can improve insulin sensitivity, reduce blood pressure in healthy individuals, protect against heart disease, and improve HDL good cholesterol (not a bad start for such a tasty food!). Dark chocolate also contains polyphenols, whilst white chocolate does not. These polyphenolic compounds are able to relax blood vessels allowing for better blood circulation, and thereby assisting with the maintenance of healthy blood pressure levels."

Coffee

KATIE SAYS: "Coffee is a really good snack, in particular if its milk-based to get the dairy in - for example, a skim latte. As long as its in moderation - daily guidelines say a maximum of three per day! And you want lots of water on top of that."

Eggs

KARA SAYS: "Yes, even the yolks are good for you! Healthy fat soluble vitamins, as well as half the protein found in an egg, are all found in the yolk!"

Avocado

KATIE SAYS: "Avocado is a healthy fat. Lots of people think its high-fat and not good for you, but its rich in mono unsaturated fats, which give you protection against heart disease. It also helps with controlling lower cholesterol levels."

nuts

KATIE SAYS: "Nuts fall into the same category as avocado - they have lots of healthy oils and fibre."

dairy

KARA SAYS: "Often milk and yoghurts are fortified with Vitamin D (a fat soluble vitamin) which requires a small amount of fat to be present in order for the body to absorb it, therefore having the full fat variety can be of value to enhance the nutritional benefits from the products' consumption. The fat in the dairy also aids with satiety, which could prevent unhealthy snacking at a later point in the day."

Potato

KATIE SAYS: "Potato always gets a bad rap as a starchy vegetable, but it's an excellent source of fibre. Sweet potato in particular is great for weight management and sugar level control. Potatoes are also really rich in potassium."

Red meat

KARA SAYS: People tend to restrict red meat unnecessarily, thinking that its high in saturated fat. "But lean red meat is high in protein, CLA (which has been found to be associated with lower body fat percentages), B12, iron and zinc. These are all nutrients we want to get into our body!"

So what happens to your brain when serotonin is reduced? Many studies say that people fed a diet low or lacking in tryptophan have increased irritability or aggression and have impaired memory and lowered mood.

For example, in once-depressed people who have now recovered, lowering tryptophan temporarily brings on a depressive relapse. This effect can even be seen in people at high risk of depression due to genetics. These people have not been depressed but are at risk of having their first depressive episode brought on by tryptophan depletion.

Similarly, animals fed a diet lacking tryptophan for one month display a significant increase in despair and exhibit anxiety-like behaviour. Open University has a module on tryptophan depletion experiments where you can learn more about its effects on mood.

You are what you eat... but do you also feel what you eat?

Better diet for better mood?

Recent research concludes that a diet low in fibre and high in refined sugars and saturated fats can also affect our mental health. We don’t know how this occurs, but what we do know is that this “Western-style diet” can change the types of bacteria that live in your gut. This may in turn affect your mood.

For example, bacteria may interfere with the hormones that regulate what you crave to eat or how much you worry about things.

Bacteria also like to eat the tryptophan in your diet. If your gut were full of tryptophan-loving bacteria, they could possibly deplete your stores of this essential amino acid. A recent study found mice without gut bacteria had higher tryptophan levels and more serotonin in the brain. When bacteria were introduced into the gut, levels of tryptophan fell. So bacteria can alter your brain serotonin – what is needed is to understand what types of bacteria are involved.

The make-up of your gut bacteria is generally stable from about the age of three years onwards. When you change your diet, you can selectively feed some bacteria making them more dominant. Similarly, you can starve some bacteria and their numbers will fall. However, most of these changes can be reversed within days of resuming your regular diet.

There is no question that a better diet begets better health. What such a diet may be and if it is the same for everyone is still an unanswered question. A new and critical piece of this puzzle is how diet – and the bacteria it supports – can affect your mood and behaviour.

Do you find that the foods you eat can affect your mood?

Paul Bertrand, Senior Lecturer in School of Health and Biomedical Sciences, RMIT University and Trisha Jenkins, Senior lecturer, RMIT University

This article was originally published on The Conversation. Read the original article.