A healthy diet plays a vital role in attaining optimal academic performance during the rigours and challenges of exam time.

Key foods and their components have been found to enhance cognitive function, improve mental alertness and enable sustained concentration to help students learn and remember the themes, concepts or formulas for their exams.

PROTEIN AND BRAIN POWER

Protein consumed from food sources provides the body with amino acids, or building blocks, to produce key chemicals such as neurotransmitters for the brain. Neurotransmitters are vital for brain cell-to-cell communication. Key neurotransmitters in terms of improved cognitive function and brain health include serotonin, norepinephrine and dopamine.

Serotonin, produced from the amino acid tryptophan, is found in brown rice, cottage cheese, salmon, red meat, carrots, peanuts and sesame seeds. It helps in the regulation of memory, learning and mood.

The amino acid tyrosine is involved in the production of the neurotransmitters norepinephrine, key to the transfer of memories to long-term storage, and dopamine, which is involved in improving motivation and activity. Tyrosine-rich foods include avocados, turkey, chicken, red meat, dairy, lentils, lima beans and sesame seeds.

The consumption of foods low in these amino acids, such as many "junk" foods, will result in low levels of serotonin, dopamine and epinephrine. This leaves students with lowered mood and concentration levels and a reduced ability to transfer learning to long-term memory.

Similarly, consuming foods high in refined sugar will lower the levels of neurotransmitters such as dopamine, resulting in decreased motivation, mental dullness and an inability to focus.

CARBOHYDRATES FOR SUSTAINED ENERGY

Carbohydrates can provide sustained energy for mental alertness and concentration for those long study periods and for three-hour- plus exams. Glucose, the energy storage form of carbohydrates in the body, is the primary source of energy used by the brain. To ensure energy is sustained, students need to be careful which type of carbohydrates they consume.

There are two primary forms of carbohydrates, complex carbohydrates and simple carbohydrates. Complex carbohydrates are found in wholegrain cereals, bread, pastas, fruit and vegetables.

Simple carbohydrates, as their name suggests, comprise single carbohydrate units such as glucose or fructose and are found in lollies, muesli bars, energy bars and drinks, and soft drinks.

In the body, complex carbohydrates are absorbed a lot more slowly. The slower absorption rate means that energy is slowly released and available for a longer time. This allows students to be more alert and able to concentrate and commit information to memory more effectively.

SUGAR BURN-OUT

Sugar burn-out refers to the impending "high" and subsequent "crash" after consuming foods containing high levels of simple or refined carbohydrates.

As the sugar from these foods is quickly absorbed by the body, there is a rush of glucose into the bloodstream, creating a short burst of energy, a "high".

The body (and brain) quickly uses up this energy and the high is just as quickly followed by a burn- out or "crash", leaving the person feeling lethargic, irritable and sleepy. Learning is not committed to memory and, come exam time, information cannot be effectively recalled.

SUSTAINING NUTRITION FOR A LONG EXAM

To ensure students have energy for that exam of three hours or more, they should eat a light meal comprising carbohydrates and protein - for example, baked beans on wholemeal toast or an egg or tuna salad wholemeal sandwich - one to two hours beforehand. If students are nervous, they should try a snack of vegetable sticks and hummus or wholemeal raisin toast around one hour beforehand. This way, their body and brain will be fuelled to go. In terms of fluids, water is best.

•The writer is assistant professor in food science and nutrition, University of Canberra.

•This article first appeared in The Conversation (http://theconversation.com), a website which carries analysis by academics and researchers.