Fuelling Your Brain: The Science and Evidence Behind Healthy Eating for Exam Success

We are in peak exam season and across the UK young people are experiencing testing times. The tips for how to optimise learning and exam success can be easily aligned to the 6 pillars of lifestyle medicine. Here I’ve focused on one of the most influential pillars, healthy eating and what the evidence suggests is the apetiser for exam success. These are my bite-size top tips:

1. Hydration: wat-er good idea!

Staying hydrated is essential for learning and memory recall. Even mild dehydration with a 1-2% drop in body water can impair short-term memory, reduce attention span and trigger headaches1. Formally measuring serum osmolality (indicating hydration) in primary school children showed an inverse correlation between hydration status and memory and mood (which will heighten pre-exam stress)2. Bringing a water bottle to the exam, results in better performance even when corrected for academic expectations based on previous course work3. “Energy” drinks are highly caffeinated and sweetened which can result in feeling jittery and anxious with knock-on disruption to sleep – avoid! Small amounts of caffeine may sharpen concentration, but it is walking a tight-rope and with the half-life 6 hours, caffeine after lunchtime will impact on sleep.

Top Tips – Set regular alarms to remind you to drink during revision, avoid energy drinks and don’t forget your water bottle for the exam. If you’re not a fan of water by itself try naturally flavouring with lemon, cucumber or fresh mint.

2. The Glucose Roller-Coaster: slow and steady wins the race

Your brain is hungry. On average, it makes up 2% of your body weight but consumes 20% of your daily energy expenditure4. This energy consumption is almost exclusively through glucose, but the intuitive solution of regular sugary snacks creates a glucose rollercoaster with a “spike and crash”. The massive dip after a sugar high leaves you irritable and “brain fogged” and the quick fix from high-sugar snacks and refined carbohydrates (e.g. white bread, sugary cereals) will cause more harm than good as proven by a Finnish cohort study showing high fat, salt and sugar consumption was associated with worse school performance5. Complex carbohydrates and whole foods with a lower glycaemic load give a more slow-release energy source and avoid these fluctuations. The HELENA (Health Lifestyle in Europe by Nutrition in Adolescence) study clearly showed a higher attention capacity in adolescents correlated with improved overall diet6.

Top Tips – Swap white bread for brown bread or wholemeal wrap. Substitute sugary cereal for porridge topped with seeds and berries. Ditch sugary snacks for nuts, seeds or popcorn.

3. Brain Fat: SMASH your exams!

60% of your brain is made of fat with omega-3 fatty acids (particularly EPA & DHA) the essential building blocks of the cell membranes that will drive those new neural connections and facilitate learning. Adequate natural intake of omega-3 fatty acids has been associated with reduced anxiety, improve attention processing speed (and longer term reduce the risk of cognitive decline and Alzheimer’s)7,8. The best sources for omega-3 fatty acids are walnuts, chia seeds, flaxseeds, hemp seeds and oily fish (SMASH; salmon, mackerel, anchovies, sardines and herrings). Sadly, aquaculture (fish farming) is impacting on nutritional levels of EPA & DHA in salmon creating huge disparities and widening health inequalities with not everyone able to afford wild-farmed sock-eyed salmon9.
Top Tips – Snack on walnuts and seeds and try to include SMASH oily fish in one of your daily meals during peak revision/exam periods. Tinned mackerel or sardines are the most affordable.

4. Breakfast: the most important meal of the day

Eating breakfast improves attention, accuracy, complex task performance, maths performance and processing speed10,11. Skipping breakfast has been promoted by the intermitting fasters but for the exams, large population studies have shown it is associated with poorer academic performance12. Participation in a school breakfast program enhanced daily nutrient intake and improvements in nutrient intake resulted in improved academic performance – a class that eats together, achieves together13. How and when you eat also will affect exam performance. Sitting an exam within an hour of having a large meal reduced scores by 8-16% in a study of nearly 5,000 adolescents in India14.

Top Tips – Make sure to have breakfast during revision periods and for the exam days, no matter how nervous you’re feeling, try to have something at least one hour before.

5. Gut-Brain Axis: happy gut, healthy mind

95% of our “happy hormone”, serotonin is produced within the gut and a whole-food, plant-based diet with minimal ultra-processed food maintains microbiome diversity and alleviates stress15. Exam periods necessitate a pragmatic approach and so the 80:20 rule of aiming for wholesome nutritious food 80% of the time and not escalating stress if 20% of dietary intake is more processed. Eating the rainbow boosts antioxidants and reduced infection risk and anthocyanin-rich berries (especially wild blueberries) have been shown to improve memory16. Green, leafy vegetables rich in iron, vitamin K, lutein and folate sharpen brain function and reduced mental exhaustion17.

Top Tips – Stick with 80:20 rule with 80% of diet whole foods or minimally processed. Include fermented foods (e.g. kefir, yoghurt) alongside natural prebiotics (e.g. onion, garlic, asparagus, bananas, apples) to feed your microbiome and boost your serotonin. Consider adding in a home-made smoothie with spinach, banana, blueberries.

Take Away Message (other than avoiding unhealthy take aways!)

Whilst healthy eating is the focus of this blog, it relates to every other pillar intricately and intimately. Improving restorative sleep, continuing physical activity, maintaining healthy relationships, avoiding/minimising harmful substances and reducing stress for mental wellbeing are all essential to build the strongest foundations for optimal performance and I will endeavour to explore each of these in similar detail in future blogs.

It is also imperative to remember that exams are not the only measure of success. A fish might fail the test of climbing a tree, but when it comes to swimming, they will SMASH it! Whether it is succeeding for exams or succeeding in swimming in the sea of life, I hope some of these tip’s help.

Good luck and Bon Appetit!

References

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