Ever wondered how the food you eat affects your grey matter? Although there are no miracle 'brain foods' that can completely protect against age-related disorders such as Alzheimer's or dementia, and there are many other medical conditions that can affect the brain, what you eat (and don't eat) can make make a difference when it comes to brain health and function. We asked dietitian Emer Delaney for her insight.


Following a healthy diet and lifestyle can provide the nutrients and conditions required for the brain to work to the best of its ability. Eating a wide variety of fruit and vegetables that contain lots of vitamins, minerals and antioxidants will help to nourish the brain and protect it from oxidative stress, which can potentially damage cells. Research suggests a healthy eating pattern – in particular, the Mediterranean diet – protects brain health. This means eating a diet rich in fruit, vegetables, wholegrains, nuts, seeds and healthy oils and fats. Research has correlated this with a slower rate of cognitive decline, lower risk of cognitive impairment and potentially a lower risk of dementia.

How do carbohydrates affect the brain?

A selection of carbohydrate-rich foods

The brain only accounts for approximately 2% of our body weight, but it consumes almost 20% of glucose-derived energy – meaning that nutrition is key for brain function.

Glucose forms the building blocks of carbohydrates and plays a role in the production of serotonin in the brain. Serotonin is a neurotransmitter that is widely accepted to be responsible for balancing mood and anxiety. The greatest source of energy for our brain comes from carbohydrate such as wholegrains, vegetables, fruit, rice, potatoes and lactose (the sugar found in in milk). These are considered healthy sources of carbohydrates that are broken down by the body into glucose and then used by our brain to function. Without an adequate supply of glucose, the brain cannot function correctly.

Some scientists propose that refined sugar can produce addiction-like effects in the human brain affecting behaviour and sleep, however there is no conclusive evidence to support this.

How do probiotics affect the brain?

It is widely accepted that there is two-way communication between the gastrointestinal tract and the central nervous system through biochemical signaling. This is sometimes referred to as the 'gut-brain axis', describing the link between the cognitive and emotional areas of the brain to our gut.

There has recently been a lot of interest in the role of probiotics, gut and brain function. It is believed that probiotics change the processing of information in the gut that is strongly linked to anxiety and depression. A small study involving 20 healthy participants found that, compared to those taking a placebo, people who took a probiotic food supplement experienced fewer negative thoughts associated with sad moods. A further small study showed that healthy women who ate probiotic-rich yogurts for four weeks had a reduced emotional response when shown photos of people who were fearful, angry or sad.

While these studies are certainly encouraging, they are limited in size and scope and further studies are needed before we can draw any firm conclusions as to exactly how and why probiotics might affect mood.

How do fats affect the brain?

A selection of high-fat, healthy foods

Specific fats are very important to the brain as they are a key component in the structure of cell membranes and they play a role in the structure and function of neurons. We know that approximately 60% of the brain is made up of omega-3 fats with DHA, a type of omega-3 fat found in fish, being the main type, responsible for eye and mental development. Omega-3 fats found in olive oil, oily fish such as salmon, herring and sardines are essential for brain development in the womb and early childhood. The majority of brain cells are developed before birth, with the remaining being laid down in the first year of life. For this reason, omega-3 fats are key during pregnancy and early childhood. There is also evidence to suggest dietary deficiency in omega-3 fats can have an adverse effect on cognition. Also, a high intake of these fats has been associated with a reduction in the development and progression of dementia. Despite these encouraging results, cause and effect has yet to be definitively demonstrated – so again, larger studies are needed before we can determine for sure the relationship between fat intake and cognitive health.

How do vitamins and minerals affect the brain?

B vitamins, vitamins C, D & E and magnesium are all essential in brain health and development. Research shows that a diet rich in vitamins and minerals from fruit and vegetables is associated with a lower risk of developing cognitive problems during aging. Thiamine and vitamin E in particular are important for cells that transmit messages from the nerves, whilst B6, B12 and vitamin C play an important role in how the nerves work and are formed. Magnesium, which is found in avocados, spinach, brown rice and nuts, improves neural plasticity, meaning the nerves are able to adapt and avoid damage. As a result, it may improve memory, help to fight stress and depression and it's crucial for the production of energy and neurotransmitters.

Epidemiologic studies also show that consumption of vitamins and minerals is associated with lower risk of developing cognitive deficits. The B vitamins and vitamins E, C, and D have all been identified as playing important roles in maintaining normal brain function. Members of the B vitamin family and vitamin C also are essential to energy production in the brain.

How does caffeine affect the brain?

A cup of coffee with coffee beans

Caffeine is widely accepted to be one of the most commonly used psychoactive substances worldwide that is found in a wide variety of foods and drinks. In small doses it is an ergogenic aid (performance-enhancing substance) acting on the central nervous system to delay tiredness and increase alertness. The caffeine found in tea may be beneficial for cognition in older adults, but may be problematic for those who have trouble sleeping. Human epidemiologic studies have reported better cognitive function amongst tea and coffee drinkers for years. A recent meta-analysis evaluating the existing evidence of caffeine and health outcomes, concluded that caffeine was consistently associated with a lower risk of Parkinson’s disease, depression and cognitive disorders for Alzheimer’s disease. However, exactly how and why this occurs is unclear from these studies.

Microbes & me

Our new series, in collaboration with BBC Future, looks at all the factors that affect our unique microbiomes – from dietary choices to lifestyle factors.

We’ve worked with dietitian Emer Delaney to bring you expert information and specially selected recipes that will help you to understand how to eat for better digestive health.

Find out more:

How does diet affect gut health?
What are probiotics and what do they do?
Does gut health affect weight?
Gut-friendly vegan recipes
Visit our Microbes & Me series hub page

This article was published on 22nd January 2019.

Emer Delaney BSc (Hons), RD has an honours degree in Human Nutrition and Dietetics from the University of Ulster. She has worked as a dietitian in some of London's top teaching hospitals and is currently based in Chelsea.


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