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Food for thought: nutrition and mental health

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Anjanette Fraser
By Anjanette Fraser, Registered Nutritionist (CABA and The Natural Alternative Health & Wellbeing Ltd) Link to Anjanette Fraser's LinkedIn profile

What we eat can have a huge impact on our brain, and insufficient nutrition can have negative consequences. So how can nutrition maximise mental health?

It’s only in the last few years that we’ve started to appreciate the link between the gut and the brain - previously we thought they were two very separate organs.

We now realise they are connected by the vagus nerve, which allows communication thousands of times each day. So those accountancy exam or job interview nerves you felt in your tummy were very real.

An unhappy mind can lead to an unhappy gut, and the opposite holds true too. It’s no surprise that if we want to maximise our mental health we also need to look after our gut.

Food that boosts the mind

Serotonin (your feel good neurotransmitter) doesn’t just belong in the brain, it’s also in your intestine walls. So eating foods which contain tryptophan - which converts to serotonin - can help. These include: milk, chicken, seeds, nuts, cheese.

Many people have Irritable Bowel Syndrome (IBS) and this is often linked to anxiety. To help reduce anxiety for people with this condition, or those with uncomfortable digestive symptoms, check if you have any food intolerances.

It’s not an easy process, but removing just one food item at a time, for two weeks, and then reintroducing the food item whilst keeping a food diary can help. Common triggers are: dairy, wheat, gluten, eggs.

Good bacteria

To improve gut and mental health it’s important to have a diverse ecosystem of good bacteria in our gut. There’s up to 100 trillion bacteria in our gut - 150 times more than human genes. We could be more bacteria than human!

Altered gut bacteria can affect how we build muscle, store fat, and can impact liver function. These in turn lead to obesity, type-2 diabetes, and heart disease, so it is important that we pay attention to this!

We know that antibiotics, alcohol, smoking and stress are some of the significant factors which affect microbiota (found in bacteria). If you’re prescribed antibiotics it’s important to complete the course and then follow on with 2-3 weeks of probiotics (from health food stores or online rather than supermarket strength products).

Probiotics and prebiotics are good bacteria, which can be obtained from food - preferably eating some form each day and including variety. Here’s a breakdown of where you can find them:


Probiotics help to support immunity, improve gut function and help with your mental health. Some dietary sources are: natural yogurt (label usually says live cultures), kefir, sauerkraut (shredded cabbage), tempeh (fermented soya bean), kimchi (cabbage), miso (fermented soybean paste), kombucha (fermented black/green tea).


This is the food that the probiotics live off, to help keep them functioning. Sources are: onion, garlic, artichoke, asparagus, banana, chicory, and generally fibre from fruit and vegetables. Careful not to eat too much of these in one day though, as they can be quite bloating.

Don’t forget Omega-3

The human brain is nearly 60% fat (dry weight)[i], therefore it could be suggested that fat is crucial for brain function. Our bodies cannot make Essential Fatty Acids (EFAs), yet they are essential for brain function – so we need to get them from food.

There are two main types of essential fatty acids; omega-6 and omega-3. Omega-6 can be inflammatory, and omega-3 are anti-inflammatory. Our typical Western diet is generally too high in omega-6 and not high enough omega-3.

  • Sources of omega-6: sunflower, sesame, primrose, corn oil
  • Sources of omega-3: fish, flaxseed/linseed, pumpkin, soybean, walnut, algae

An Australian study found people with severe depression had an altered omega balance with too low omega-3. Further clinical trials found benefits after just eight weeks[iii].

Fish are one of our best sources of omega-3 (more so than flaxseed/linseed, walnuts pumpkin, soybean). They’re also a great source of protein (keeping you fuller for longer) and benefit your joints, skin, cholesterol as well as mental health.

Studies suggest that we should eat fish at least twice per week, and one of which should be oily. If you’re not keen on eating fish you can take a fish oil supplement, and if vegetarian or vegan algal oil is available through health food stores.

Take your vitamins

Serotonin is made from tryptophan which needs vitamin D to make it active. Low vitamin D levels have been linked to poor mental health[v]. We’re only just beginning to discover the full benefits of vitamin D.

The best source of vitamin D is the sun. In the Southern part of the UK our bodies are only able to make vitamin D from the UVB rays from April to October - but not through sunscreen, clothing, make-up/moisturisers (with an SPF factor).

It is suggested that we get 20 minutes of sun exposure per day for pale skin, and longer for darker skin. There can be a risk of over sun exposure, so if you are in doubt it may be safer to take vitamin D as a supplement (10mcg of vitamin D3 daily). We should certainly all be doing this from October to April.

Other sources of vitamin D are oily fish, and egg yolk.

B vitamins

If your energy and mood is low it could be low in B vitamin levels. If you are vegan (or vegetarian) it’s recommended to take a B12 supplement as sources are from animal products.

As we age it’s more difficult to absorb B12 so if you’re feeling low in energy and your mood is also low a simple blood test with your GP can test your B vitamin status.

Anjanette is the Chartered Accountants Benevolent Association’s (CABA) expert in nutrition. With a background in business and finance, she has been providing nutrition seminars and webinars since 2005.

CABA support past and present ICAEW members, ICAEW staff, ACA students and their close families from across the globe.

Further information can be found in Anjanette’s Food for thought webinar and Bitesize Nutrition podcast.