29 June 2015

How diet and physical activity affect brain function – Part II

In this article DietDoc takes a more detailed look at specific foods that have been identified by researchers as protective against brain deterioration.


In Part I we discussed dietary factors that can influence brain function and possibly prevent loss of cognitive ability as we age. We emphasised that diet and lifestyle, especially exercise, may help to stem the prevalence of Alzheimer’s disease among our senior population.

In this article we will take a more detailed look at specific foods that have been identified by researchers as protective against brain deterioration.

Foods that can improve brain function

a) Omega fatty acids (FAs)

Omega fatty acids, especially omega-3s have long been identified as “brain food” for people of all ages. Eating foods rich in omega-3 fatty acids such as fatty fish at least 3 times a week may slow mental deterioration in the elderly. Omega-3 supplements are also freely available at varying prices.

b) Polyphenols

As the name implies, polyphenols are chemical compounds that contain a number of phenol groups in their structure. They are classed as powerful antioxidants, which means they can counteract the damage caused by reactive oxygen species or ROS believed to cause deterioration of brain cells. The astringent taste of strong tea or red wine is an indication that these products contain high levels of polyphenols.

Read: Ten sources of antioxidants

Well-know foods and drinks that are rich in polyphenols include:

- Black tea, green tea, red wine, cacao and coffee are major sources in the diet.

- Flavonoid-containing plants such as parsley, celery, citrus fruits, herbs like oregano, soy and soy products, onions, leeks and broccoli, berry fruits (particularly blueberries), kiwi fruits, plums and apples, peanuts green tea, red wine and chocolate.

- It is interesting to note that most of the above mentioned foods form part of the Mediterranean diet. This may be another reason why this diet has been found to be so healthy and can help us remain cognitively active.

Read: Mediterranean diet good for the brain

The positive effects of polyphenols and/or flavonoids include the following:

- Reducing the risk of dementia, improving cognitive function, and boosting cognitive development over time, including improved learning ability

- Memory enhancement

- Neuron protection and reduced neuro-inflammation, which may be one of the factors responsible for damaging the nervous system and brain.

According to Meeusen, “consumption of polyphenol-rich foods throughout life holds the potential to limit neurodegeneration and to prevent or reverse age-dependent deteriorations in cognitive performance.” He does, however, caution that “the therapeutic and pharmacological potential of these natural compounds still remains to be translated to humans in clinical conditions.”

In other words, we can recommend that people should eat plenty of foods that contain polyphenols throughout their lives, but need to remember that many of the over-the-counter pills that promise eternal youth and brain power may as yet not be worth buying.

c) Branched-chain amino acids

Anyone who has ever purchased an amino acid mixture for muscle building at a pharmacy or gym will have seen that such products contain “branched-chain amino acids”. Leucine, isoleucine and valine are called branched-chain amino acids (BCAAs) and they play an important role in brain physiology. BCAAs help the brain to produce protein, 5-HT (5-hydroxytryptamine or serotonin, is an important “brain messenger” and also combats depression), dopamine and noradrenaline (other “brain messengers”).

For sports purposes, the BCAAs are intended to prevent fatigue, and more recently they have been suggested as brain power stimulants, but this has as yet not been proved by means of scientific experiments.

Read: Brain chemistry uncovered

In South Africa most people tend to eat a lot of protein foods that supply BCAAs. So if these amino acids do prove to be vital for brain function, it will not be necessary for most South Africans to use supplements provided that we eat a moderate portion of meat, fish, eggs, or cheese regularly and use milk daily.

d) Tyrosine

Another amino acid called tyrosine which is found in most high-protein foods including soy products, chicken, turkey, fish, peanuts, almonds, avocados, milk, cheese, yoghurt and sesame seeds may help to reduce the negative effects of stress on cognitive function.

Most people are aware of the fact that stress and/or lack of sleep can make it really difficult for you to maintain your brain function and think clearly. Meeusen states that “the majority of evidence suggests that tyrosine is useful as an acute treatment to prevent stress-related declines in cognitive function”.

e) Caffeine

Beverages that contain caffeine have been used as a “pick-me-up” for the body and the mind for a long time. Moderate intakes of coffee, tea and cacao will provide sufficient caffeine to stimulate brain activity without causing the negative effects of caffeine overdose such as insomnia, tremors, nervousness, anxiety, gastric upsets etc.

Read: Caffeine gives erectile boost

Overdoing caffeine intake in various ways (drinking too much coffee, using caffeine-laced energy drinks and taking so-called “ergogenic aids” to improve performance in various fields including brain function), is counterproductive and should be avoided.

Caffeine is a diuretic which increases the loss of fluids by the body which can affect brain function negatively. Too much caffeine has the potential to dehydrate the body and the brain, leading to poor performance both physically and mentally.


It is evident that researchers still have a long way to go to identify exactly which foods and which components in foods are the most beneficial when it comes to maintaining brain function and preventing deterioration of our “little grey cells”.

In the interim it is good to keep in mind (excuse the pun) that these protective foods need to be used in moderation for a lifetime and be combined with regular exercise (see last week’s article) to achieve a healthy mental state and prevent Alzheimer’s and other diseases of cognitive decline.

Read more:

The balanced diet

Regular exercise adds years to life

Keep your mind sharp


- Meeusen R (2014). Exercise, nutrition and the brain. Sports Medicine:44, (Suppl 1): S47-S56.

Image: Human brain from Shutterstock

Dr Ingrid van Heerden is a registered dietician and holds a doctoral degree in Nutrition and Biochemistry. She believes that "we are what we eat" and offers free nutrition and weight loss advice via her DietDoc service on Read more of her articles.


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