By David Veale and Venetia Mitchell
Our most recent blog explained the science behind the gut-brain axis, highlighting the important relationship between our gut microbiota and our brain. Our first blog covered the gut microbiome, with practical dietary and lifestyle strategies aimed at improving mood and overall brain health.
This blog focuses on how to identify nutrient-dense foods that have been linked to optimal brain function. We also cover tips on how to include these mood improving foods into your diet.
Why are nutrient-dense foods important for brain health?
Dietary and lifestyle strategies have been shown to work for the prevention of many conditions, such as heart disease, obesity and diabetes. Whilst diet is not yet considered a treatment for mental disorders, a 2012 SMILE trial in depression showed interesting results, with a third of the participants who made dietary changes over a three-month period going into remission and experiencing relief from their depressive symptoms. This was superior to a control group receiving social support. This study has since been replicated by another group in Australia who found similar results.
Many ingredients in processed foods have been shown adversely to affect the health of our gut microbiota, so moving to plant-based whole foods is recommended.
We highlight these dietary strategies within this blog and give practical tips on how to implement them.
Do you make a conscious effort to avoid processed foods?
Poor diet can be detrimental to our mental health. Processed foods are generally convenient, cheap and engineered to taste great. For example, processed chocolate, containing sugar and poor quality fat, does not have any health benefits. It just gives us that instant hit. Elements commonly found in such foods, such as artificial sweeteners and emulsifiers, may alter our gut microbiota, which may cause dysfunction to the gut-brain axis.
Savoury processed foods, such as ready meals, tend to contain additives and to lack the essential dietary fibre and protein required for healthy, slow absorption. As a result, these foods trigger our brains to overeat.
Food researchers have recently been debating whether processed foods are addictive, providing behaviours similar to what we see from the consumption of cigarettes and alcohol.
Refined carbohydrates, such as white rice or white flour can also mess with slow absorption. These grains are stripped of the brown husks that provide us with essential nutrients and, most importantly, dietary fibre. The instant hit from consuming them causes the body to bring the blood sugar right down in response. The result is often a poor mood swing and a yearning for more food. Opting for whole grains makes us feel more satisfied by slowing our digestion to adequately absorb the nutrients, gain the fibre and feed our important gut microbiota. Meats such as salami, poor quality ham, sausages and bacon are also all highly processed.
How do you spot if a food is processed?
Generally, if the food contains more than five ingredients, especially if there are some you don’t recognize, it is processed.
We may be persuaded to believe that foods labelled ‘vegan’ and/or ‘gluten free’ are naturally healthy for us. But these can be heavily processed too.
So what do we mean by ‘plant-based whole foods’? And what foods support brain health?
A good way to ensure you are consuming whole food is to fill your plate with 90% plant-based food.
The best science we have explains that mood may be improved when we consume a modified Mediterranean diet, rich in nutrient-dense foods.
A Mediterranean diet is mainly rich in vegetables, some fruit and whole grains: with an emphasis on oily fish (salmon, trout, sardines, mackerel…), olive oil, legumes (chickpeas, butterbeans, cannellini beans, red beans) and raw unsalted nuts. Moderate consumption of lean red meat and dairy is included.
Many of these foods from the typical Mediterranean diet provide the raw materials required to make our brain chemicals. For example, serotonin (important for regulating mood) is made from the amino acid (protein) tryptophan which is found in foods such as eggs, legumes, seeds, meat and fish. For our bodies to convert the tryptophan into serotonin, it requires nutrients.
On this basis, it makes sense to consume these protein-rich foods in combination with further nutrient-dense foods.
A recommended podcast to help understand this more is Felice Jacka on The Doctors Kitchen
What do we mean by nutrient-density when it comes to food?
Nutrient-density refers to the ratio of a food’s nutrient value to its calorie content. Essentially, nutrient-dense foods have not been ‘diluted’ by the addition of energy from added fats and sugars.
Many key nutrients are termed ‘essential’ because our bodies cannot produce them. We must get these nutrients from our diet. These include essential fats such as polyunsaturated fats that we gain from olive oil and oily fish. Further nutrients also found to support mental and physical health include vitamin A, Thiamine (vitamin B1), vitamin B6, Folate (vitamin B6), vitamin B12, and vitamin D and minerals such as zinc, magnesium, iron and selenium.
Many whole foods are high in these nutrients without being highly calorific.
What are the best nutrient-dense whole foods?
Foods such as watercress, lettuce, spinach, dark green salad leaves, beetroot, Swiss chard, kale, basil, parsley, cauliflower, red cabbage, tomato, cherry, lemon, strawberry, cocoa, chestnuts, chia seeds, sunflower seeds, flaxseed, soybean, fava beans, nuts, oily fish, oysters, liver and offal, and goat meat all score highly as nutrient dense foods (see diagram below).
Diagram to Represent Nutrient-Dense Foods
There is evidence that the above food recommendations help support the prevention of mental and physical health conditions. They are designed to be incorporated into a whole-food dietary pattern of your choice. Here we give some guidance to carnivores, vegetarians and vegans.
An important part of a healthy diet for depression and other mood disorders is the inclusion of animal products such as seafoods, organ meats, and small amounts of other traditionally raised, minimally processed meats. We recommend:
1. Eat expensive, better quality meats infrequently rather than cheaper, poor quality meats more often
Eat less and buy better grass-fed animals. The best places to find this can be your local butcher or an online specialist such as Field and Flower who source British grass-fed meat. Grass fed animals provide healthier meat than grain fed animals do because their diet contains a higher level of omega 3 fatty acids and antioxidants.
Fish is less obvious. Some of the cheaper fish, such as mackerel, herring and sardines are the healthiest. You may like to visit your local fishmonger and ask them questions such as, “do you have any line-caught fish in?”, or “where did these salmon, oysters and mussels come from?” Or order online at somewhere like Eversheds, where the fish is sourced from local UK shores and is sustainable.
2. Focus on smaller fish – beware of the toxic load in predatory fish
Smaller fish (mussels, oysters, mackerel, sardines, anchovies) are less likely to be high in toxins, unlike larger species (tuna, seabass, monkfish). Larger species are higher up in the food chain and therefore contain a higher toxic load (e.g. mercury).
Topping a salad or plate of steamed vegetables with smaller fish such as sardines or anchovies gives you healthy fatty acids with less toxins. These fish can be bought in tins too – economical and easy.
3. Make animal products more of a topping or a treat
Eat mostly plants and plant-based protein (see below) and include animal products as high quality treats.
What suits you? In general we recommend:
- Meat: buy the best quality you can afford. Eating not more than 4-5 palm-sized portions a week, with a focus on red lean meat (venison, beef) that is grass fed, and smaller amounts of poultry (chicken, turkey) is sensible
- Fish and seafood: 2-3 palm-sized portions a week (with the majority being oily fish)
Easy, fun and good recipes include these lovely mussels that you could enjoy with a portion of steamed vegetables, with a smattering of extra virgin olive oil and herbs.
Or, for a quick lunch or midweek supper you may like to enjoy Liver on Sourdough Bread. It is a good idea to complement this with dark green salad leaves or vegetables, freshly steamed or roasted.
Cookbooks such as The Roasting Tin by Rukmini Iyer give some simple, quick ideas on cooking fish, seafood and meat. We also recommend further cookbooks and recipes below.
Vegetarians and vegans
If you are a vegan or vegetarian then you are ahead in terms of plant-based eating, which is great news. Be conscious however, that vegan alternatives may have hidden artificial ingredients which place them in the category of processed food!
Ensuring there is enough protein in your diet is important. If you don’t eat adequate protein at every meal, you can end up being anxious, depressed, hungry, and tired. It is a good idea to ensure you consume a complete plant-based protein such as tofu with your meals. Legumes such as lentils and chickpeas should be combined with small amounts of a wholegrain, such as brown rice, buckwheat or bulgur wheat in order to make them a complete protein.
Legumes can either be soaked and cooked. If you are short of time, tinned legumes are perfectly acceptable and both options mean that you can eat well for a reasonable price. Legumes are easy to cook in a pressure cooker or slow cooker too.
Tip: Making positive dietary changes may bring digestive discomfort for some people, particularly if you are not used to consuming legumes. Start slowly, and build up the number of portions over the weeks. If you have further trouble, you may like to seek help from a health professional.
Tips to ensure you get this ‘complete protein’ from your diet:
- BBC Good Foods’ Tofu, Butternut and Mango Curry or
- Ottolenghi’s Simple, Puy Lentil and Aubergine Stew served with a grain of choice such as buckwheat or brown rice or,
- Simply place ½ tin of Hodmedods Vaal Daal on a slice of sourdough bread, topped with salad leaves, herbs and oils
The science does suggest however, that these plant-based proteins may not support optimal levels of Vitamin B12 required for adequate brain function. If you are a vegan, you may wish to seek advice and monitor your levels of micronutrients through your GP or another health professional.
Further recommended books include: Dr Gemma Newman: The Plant Power Doctor or Max La Manna: More Plants, Less Waste or online, have a look at the recipes from Hodmedods who source pulses and grains from British farmers.
So, mainly whole foods, and plant-based…. but we must not forget the fibre, polyphenols and probiotics which all feed our gut microbiota!
We identified the importance of prebiotic fibres, polyphenols and probiotics to support the gut-brain axis in our first blog.
Dietary fibre is a type of carbohydrate that your body cannot digest. It is vital for our health and comes from plant based foods in different forms:
- Soluble Fibre is an example of a prebiotic because it feeds our beneficial gut microbes
- Insoluble Fibre cannot be fed on by the gut but it is crucial to bulk out our stools and help food pass through the gut. This ensures we excrete toxins.
Many plant-based foods contain both soluble and insoluble dietary fibre making it difficult to categorise the foods into either type.
The majority of us simply get 20g per day, when we should be consuming 30g per day. This fact sheet provides further information on intake.
The most fibrous nutrient dense foods include Jerusalem artichokes, asparagus, leeks, apples, chicory root, lentils, beans, onions, garlic, bananas, beetroot, broccoli, fennel root, wholegrain (oats, rye, buckwheat, bulgur, brown rice, popcorn, bulgur and barley). In particular, we can gain dietary fibre from chia seeds or flaxseeds (aka linseeds).
So to ensure you are getting enough of the best fibre, you may like to try these ideas:
- Overnight Oats, made with the wholegrain oats and chia seeds, plus do add on other nuts and seeds
- Eggs on sourdough toast, sprinkled with ground flaxseeds (simple to do in something like a Nutribullet)
- Roasted artichokes as a starter or side dish
Improving dietary fibre comes naturally when we consume at least 50 different ingredients a week, including 30 different vegetables with plenty of legumes (kidney beans, split peas, fava beans, chickpeas, black beans), seeds (chia seeds), nuts (almonds) and herbs, with a focus on all of the colours of the rainbow.
Reminder: Do you make a conscious effort to be diverse with your food choices? We often fall into sticking to the same breakfast each day and purchasing the same products from the supermarket each week. Why not try a 30 different plant challenge as recommended here by Professor Tim Spector?
With a plate of food full of the colours of the rainbow, we will naturally be consuming foods rich in polyphenols (read more about polyphenols in the first blog of this series).
These plant phytochemicals tend to be highest in foods that are rich in colour. For example, deep coloured vegetables and fruits, a glass of red wine, berries or a square of dark chocolate (needs to be at least 85% cocoa). Our gut microbes ferment the plant polyphenols into active substances known as antioxidants which protect our brains from inflammation and environmental stress.
Tip: Green tea is rich in antioxidants and contains an amino acid which increases levels of brain chemicals, helping to reduce anxiety. Although it contains some caffeine, people who find the caffeine in coffee and tea hard to tolerate may find green tea a good alternative.
Fermented foods and nutrient density
Fermented products containing probiotics also help to support our gut microbiome health. Some of these probiotics living in our gut help our bodies produce essential vitamins. The fermented foods, listed below, contain strains of probiotics such as Bifidobacterium which helps to promote the production of vitamin B9 (folate) within our gut.
- Milk kefir
- Raw milk cheese
- Kimchi or sauerkraut
- Kombucha drink
These products can be found on many supermarket shelves. However, they can be produced at home cheaply. Good books to guide you include either The Art of Fermentation or Wild Fermentation by Sandor Ellix Katz. There are also plenty of recipes online such as this quick and easy Kimchi recipe or this Kombucha one. Kombucha requires you to have a ‘scoby’ and Kefir requires ‘kefir grains’ which are rather like a sourdough starter (a natural yeast). These can often be purchased or gained free from a friend or someone within a local community. There are Facebook groups such as UK Fermenting Friends which you can join for encouragement and advice.
A high quality Kefir that we recommend is from the Chuckling Goat. You can buy in bulk as a bottle lasts up to 4 months. Add 1-2 teaspoons of it into a smoothie, porridge, or yoghurt based bowl daily to support your gut.
Sourdough bread is made using a fermentation process. Probiotics in the starter (natural yeast) used to make sourdough enable early breakdown of the grain. This improves the nutritional value of the bread, making it healthier for our digestive system. As we mentioned in our first blog, you can join the Sourdough Club to learn and gain support in producing your own bread. They send you a starter when you join and it’s a lovely community to be part of.
Science tells us that various nutrients are good for our brain health. Promising science finds dietary strategies may be considered within a treatment plan for someone with depression. Right now, it is a secondary strategy for treating mental disorders, yet we know it is so key to overall physical health.
Replacing the processed ‘quick fixes’ with foods high in nutrients and fibre makes sense. This whole food, plant-based approach does not have to be expensive.
- A little planning saves time and pennies: stock the cupboards with the right ingredients, write a shopping list OR, order a box of fresh vegetables, meat and fish etc. to your door (see below)
- Pick at least a few different recipes to try each week to help ensure you are eating well, with diversity. There is nothing wrong with cooking more of one dish to enjoy a day or two later.
Functional Nutrition Cookbook by Lorraine Nicolle and Christine Bailey (a chapter is dedicated to supporting balanced brain chemistry)
The Roasting Tin by Rukmini Iyer
The Plant Power Doctor by Dr Gemma Newman
The Sourdough School Book by Vanessa Kimbell
More Plants, Less Waste by Max La Manna
The Art of Fermentation by Sandor Ellix Katz
Ideas of where to shop
Find a local farmers market (often cheaper than the supermarket)
Field and Flower (british grass-fed meat)
Eversheds (british fish, seafood and grass-fed meat)
Buywholefoodsonline (bulk buy nuts, seeds and grains)
Hodmedods (legumes, seeds and grains)
Eaten Alive (fermented food products)
Chuckling Goat (high quality kefir – fermented)
Note: There are three blogs in this series. The first blog discussed the Gut Microbiome and Mood. Find out more about Understanding the Microbiota-Gut-Brain-Axis: The Science in the second blog.
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Firth et al (2019) The Effects of Dietary Improvement on Symptoms of Depression and Anxiety: A Meta-Analysis of Randomized Controlled Trials. Psychosom Med. 2019 Apr; 81(3): 265–280
Jacka, F. et al (2017) A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial) BMC Med. 2017; 15: 23 and Nutr Neurosci . 2018 Sep;21(7):487-501
Knight et al (2015) A randomised controlled intervention trial evaluating the efficacy of a Mediterranean dietary pattern on cognitive function and psychological wellbeing in healthy older adults: the MedLey study. BMC geriatrics. 2015;15:55
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Parletta et al (2019) A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutritional Neuroscience 22:7,474-487, DOI: 10.1080/1028415X.2017.1411320
Williams et al (2020) The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review. Plant Foods Hum Nutr. 2020 Mar;75(1):12-23
Lacahnce, L, & Ramsey (2020) Antidepressant foods: An evidence-based nutrient profiling system for depression. World J Psychiatry. 2018 Sep 20; 8(3)