Food for thought: how our diet affects our brain

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The brain is always ‘on’ – it controls our movements, thoughts, feelings and actions, our heartbeat and breathing, our sleep, and our senses. As a result, our brains need a constant supply of fuel, which it sources from the food that we eat.  The brain is the most metabolically active organ in the body. It comprises only 2% of our body weight, but this metabolic powerhouse manages to consume 25% of all the glucose in our blood.

The effects of some foods on how we think, act, and feel are well known; sugar gives us a ‘high’, caffeine stimulates the brain, and chocolate makes us happy. More recently, the idea that nutrition can elicit non-observable effects on the brain has emerged. A growing body of evidence now exists to demonstrate the effects of nutrition on brain development, mood, cognition, and ageing.

How our food affects our mood.

Our mood is the product of chemicals in the brain, including various neurotransmitters. Serotonin, known as the ‘happy hormone’, is produced in the brainstem, but has widespread effects on the brain and the body. Serotonin helps control our mood (feeling happy as well as sad), our sleep, appetite, and our memory.

Serotonin is made from tryptophan, which is an essential amino acid. Essential amino acids cannot be produced by the body, so we need to get them from the foods that we eat. Foods like chicken, fish, red meat, cheese, nuts and seeds are high in tryptophan, so their consumption allows the production of serotonin in the brain and the body.

Whilst eating a diet rich in tryptophan doesn’t necessarily increase the amount of serotonin in the brain, the inverse can have dramatic effects. The brain can’t cope with a tryptophan-free diet, and levels of serotonin will quickly decrease, resulting in irritability, anger, lowered mood, and poor memory.  

Interestingly, about 90% of the serotonin in our bodies is produced in the gastrointestinal tract, not the brain. Recently, the gut has become known for a lot more than simply digesting our food. Now dubbed the ‘mini-brain’, the gut has been shown to play a role in regulating our mood, appetite, and cravings for particular foods via the brain-gut-axis. Studies have also shown that when people supplement their diets with probiotics, or ‘good’ bacteria for the gut, they experience decreased anxiety, and improved mental outlook.

The typical ‘Western’ diet consists of highly processed food, which is high in refined sugar and saturated fats. Research has shown that this type of diet can actually affect the gut-brain signals about internal states like hunger and satiety, making it more difficult for our brain to recognise when we are full. 

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Nutrition and neuropsychology.

Nutrition can alter brain function in the short-term, by altering levels of neurotransmitters and subsequent firing of neurons, but it can also alter brain structure and function in the long-term.

The importance of proper nutrition during brain development in infants and children is well established; in babies, around 87% of their daily energy intake supplies the brain. Throughout infancy to early childhood, the growth of neurons and neuronal connectivity is at its greatest, and therefore glucose requirements are high. Poor nutrition has been shown to put children at a greater risk for mental illness, and behavioural problems like aggression and attention deficit hyper-activity disorder (ADHD). 

The food we eat has a direct effect on our cognitive functions, such as memory, attention, concentration and cognitive control. The effects of poor diet on sleep, energy and mood can also indirectly affect our daily cognitive function. Those who eat diets high in processed food, saturated fats and refined sugars have been shown to have poorer memory than those adopting a healthy, balanced diet.

The lack of sufficient nutrients can also have a toxic effect on the brain (neurotoxicity), particularly for older individuals, which predisposes the brain to atrophy (shrinkage) and premature neuronal loss. A longitudinal study found that low intake of nutritious foods, and high intake of unhealthy foods were each associated with smaller hippocampal volume; the memory centre of the brain. Recent research has focused on specific nutrients that may confer neuroprotective effects in later life, which may ameliorate neuronal loss in particular brain regions, and slow cognitive decline.

Food for thought, and healthy brain function.

A number of specific foods and nutrients have been identified to positively influence brain health, and protect against the effects of ageing on the brain.

Omega 3 fatty acids

Known as the “good fats”, Omega 3 fatty acids are found in fish, avocado and flaxseed.

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B vitamins and Folate

Folate has been shown to reduce the risk of age-related cognitive decline, and enhance the effect of antidepressant medications when used concurrently, while B vitamins are essential for a number of cellular and metabolic processes. High concentrations of folate can be found in green leafy vegetables, legumes, nuts, yeast, and wholegrains. Nuts and wholegrains are also rich in B vitamins, as are unprocessed meats, cheese, and eggs.  

Plant-based antioxidants

Various plant-based micronutrients have antioxidant properties, which can prevent oxidisation and cell damage in the brain and body. Some examples of these micronutrients include:

Polyphenols

Polyphenols are predominantly found in fruits and vegetables, especially blackberries, blueberries, raspberries and goji berries; mangoes, grapes, garlic, onions and kale. They are also found in green and black tea, as well as coffee and dark chocolate (yay!).

Curcumin

Curcumin is found in turmeric, and has been shown to promote healthy brain ageing via its anti-inflammatory properties.

Vitamin E

Vitamin E is another antioxidant that has been shown to promote healthy function in the ageing brain. You will find it in green leafy vegetables, nuts and some plant-based oils like grapeseed, sunflower, and olive oil.

Minerals

Minerals like zinc, iron and magnesium all play important roles in promoting optimal brain health and neurological function. Zinc is abundant in lean meats, seeds, nuts and oysters, while iron is found predominantly in red meats, as well as grains, nuts, and spinach. Nuts, legumes and leafy greens are also rich in magnesium.

Thankfully, there are plenty of foods on offer that are rich in nutrients that promote neurological function and healthy brain ageing. Whilst it doesn't mean we should go out and gorge on good fats until the cows come home, the next time you accidentally eat a little too much dark chocolate, or one (seven?) too many almonds, you can rest assured that your brain might actually thank you for it in the long term.