• We tend to eat habitually, choosing foods and flavour profiles that are familiar.
• We need to approach changes to your eating with openness and patience
• It's best to try new foods when you are in a good mood and to approach them with a sense of curiosity.
• Prepare to form some new, manageable habits.
• The most important factor when it comes to building new eating habits is repetition.
• To make repetition achievable, your new behaviours should be small enough that they are manageable even at your most tired.

• A whole-food, plant-heavy, fibre-rich diet might reduce depression risk through its anti-inflammatory qualities, through its effects on gut microbes and via other pathways.
• Approach changes to your eating with openness and patience. Give healthy new additions to your diet a few chances if needed, and experiment with different ways of preparing the food. Prepare to form some new, manageable habits.

• In the context of an overall healthy diet, there are limits to the health benefits of supplementation.
• Therefore, it would be best to try to increase our consumption of plant foods, whole grains and oily fish.
• There might be a role for the targeted use of supplements to help protect brain health and support mood.

Supporting a healthy and diverse gut microbiome is likely to be beneficial to mood regulation. The primary food for the population of gut microbes is fibre, acquired by the consumption of a broad range of wholegrains and plant foods – nuts, seeds, herbs, spices, legumes, fruits and vegetables.

If we consume insufficient dietary fibre, the balance of microbes becomes perturbed and the protective mucus lining of the gut is depleted, leaving the gut cells vulnerable. In this condition, the junctions of the gut lining can slacken, permitting the transfer of gut bacteria into the bloodstream.

Your gut microbiome benefits from a diverse range of plant foods. While there are 300,000 edible plants on the planet, we eat just a tiny fraction of these, around 200. Recent research suggests it would be good to aim for 30 different plant foods per week. This might sound daunting, but remember that fruits, vegetables, nuts, seeds, beans, wholegrains, herbs, and spices count as plant foods. And yet more than half of our calories come from just three plants: corn, rice and wheat. Clearly, there is some work to do.

There is an even faster way to increase the diversity of your gut inhabitants: fermented foods. Fermented products – foods and drinks that have undergone bacterial fermentation – have been a feature of traditional diets around the world for thousands of years. They include kimchi, kombucha, kvass, boza, togwa, kefir,  cheese, yogurt and dozens more. Originating as ways to preserve the harvest and supply nourishment through long, cold winters, these foods are now understood to play a beneficial role in gut-microbial diversity and, by extension, our health.

A Western-style diet – high in added sugars, refined carbohydrates, processed meat, fried/fast foods and saturated fats – is associated with increased depression risk in adults and more inflammation and depression in adolescents. There is also evidence that a Western-style diet can impair memory function and appetite control within just a week.

Adolescents are prime consumers of sugar-sweetened soft drink, which is of concern in light of research showing that, within just three weeks, moderate consumption of these products increased inflammation in healthy males.

Alcoholic beverages can, in excess, be detrimental to mood, and research indicates a relationship between excessive alcohol consumption and major depression. Try to stay within or below national recommendations for healthy consumption. If you struggle to control your alcohol intake, contact your GP to find out about support services in your area.