Can eating the rainbow support healthy cognition?

In this blog, Clinical Neuroscientist Miguel Toribio-Mateas discusses the benefits of a diet full of colour for healthy cognition and different brain processes; from memory to reaction time.

Cognition refers to a range of processes relating to the acquisition, storage, manipulation, and retrieval of information by the human brain. It underpins nearly all of our daily activities, in health and disease, across the age span.

Cognition can be separated into multiple distinct functions, dependent on particular areas of the brain or “brain circuits” that work based on a number of natural chemicals known as neurotransmitters. Neurotransmitters are created by the body using building blocks that come from nutrients, hence the importance of being aware of what foods can act as sources of the necessary active components of the molecules that drive our brain processes.

Areas of the Brain Involved in Cognition

The word “cognition” originally comes from the Greek verb “gignosko”, meaning to recognise, perceive and know [1]. More specifically cognition refers to the intellectual processes of acquiring, understanding and using information and transforming it into knowledge through experience, thinking and the senses. The mental actions that characterise cognitive function help human behaviour adapt to new situations and people to adopt new preferences [2].

Cognitive processes can be divided into four to six neuropsychological domains including learning and memory, visuospatial and motor function, attention/concentration, language, social cognition/emotions and executive functions. Building on the research previously carried out by the Institute, this report focuses on memory, attention, executive functioning and reaction time / processing speed. Each domain contains specific functions that provide humans with basic and more complex capabilities that contribute to their personal intellectual skills and knowledge [3].

Feeding your cognition

Nutrition can substantially influence the development of brain structure and function. Indeed, nutrition provides the proper building blocks for the brain to create and maintain neural connections, which are critical for improved cognition. Dietary factors have broad and positive actions on neuronal function and plasticity. Brain function is undoubtedly dependent on adequate nutrition, and short-term variations in the amount and composition of nutrient intake in healthy individuals may influence measures of cognitive function [4].

Understanding relationships between food choices, diet and cognition is necessary to uncover mechanisms involved in and strategies to optimise cognitive performance. This blog aims to provide the reader with insights from the best research evidence available on the subject, as well with a translation of the same into practical applications for everyone, whether you’re a healthcare practitioner or simply have a keen interest in nutrition for brain health.

Whole Dietary Patterns, e.g. the Mediterranean diet

A large amount of good quality scientific literature describing the effects of whole dietary patters such as the Mediterranean diet has been published to date. By quality I mean systematic reviews, meta-analyses, randomised controlled trials and cohort studies. The most prevalent whole dietary pattern emerging as a theme within the result findings is the Mediterranean dietary pattern. It is extremely well reported as being positively associated with better cognitive function, as well as with reduced risk of degenerative conditions such as Alzheimer’s disease / dementia and Parkinson’s. A large proportion of this effect is attributed to the diversity of the brightly coloured fruits and vegetables, legumes / pulses, oily fish, nuts and seeds and whole grains present in cuisines around the Mediterranean, as well as to extra virgin olive oil (EVOO), which scientists are now finding to be depending on your gut flora. That means that gut microbes fed a more diverse diet will enable you as a human to extract more “goodness” out of your food – which in technical terms is called “increased bioavailability of nutrients” – and this results in overall better cognition.

For example, a recent systematic review of longitudinal and prospective trials published between 2000 and 2015 [5] found that the specific cognitive domains that have been found to benefit from adherence to a Mediterranean Diet pattern are memory (delayed recognition, long-term, and working memory) and executive function, as well as visual constructs.

These domains have also been identified in a large systematic review and meta-analysis by Loughrey et al [6]. The authors analysed 15 cohort studies with a total of 41,492 participants, plus 2 randomised controlled trials (RCTs) with 309 and 162 participants in intervention and control groups, respectively and found the strongest evidence of association between the beneficial effect of the MedDiet and global cognition in adults. Meta-analysis of cohort studies revealed a significant association between adherence to the MedDiet and episodic memory but not working memory or semantic memory. Working memory has been defined as memory “active and relevant only for a short period of time” [7], whereas episodic memory is a longer lasting memory that allows people to recall and re-experience personal events [8]. Meta-analysis of RCTs revealed that compared with controls, the MedDiet did improve global cognition, including working memory and delayed recall but that the effects on episodic memory, attention, processing speed or verbal fluency were not significant. Overall, this large study highlights the undisputable benefits to cognitive function of this dietary pattern.

Is what’s good for the heart good for the brain?

Studies have shown the adherence to the MedDiet contributes to a reduced risk for coronary heart diseases and metabolic syndrome including hypertension and dyslipidaemia (high LDL or “bad” cholesterol levels). The presence of cardiovascular and metabolic conditions increases the risk of development of cognitive impairments [9-11] so, as a rule of thumb, what is good for the heart tends to also be good for the brain.

Might it be the Extra Virgin Olive Oil (EVOO)?

Of all of the individual components characteristic of the MedDiet, olive oil is possibly the one contributing most strongly to the prevention of cognitive decline in those adhering to this dietary pattern, as confirmed by a recent systematic review of 56 studies conducted by researchers at the Division of Human Nutrition and Health of Wageningen University in The Netherlands [12]. Extra virgin olive oil (EVOO) is a rich source of polyphenols such as hydroxytyrosol and oleocanthal, known to have a strong neuroprotective effect [13]. Studies from countries around the Mediterranean seem to agree. Like the recent French NutriNet-Santé cohort study wherein a large sample of 6,011 men and women over 60 years of age, adherence to the MedDiet resulted in fewer subjective memory complaints [14].

In Spain, the now famous PREDIMED (Prevención con Dieta Mediterránea) study was a 5-year randomized clinical trial on the use of the Mediterranean diet versus a control diet for primary cardiovascular prevention in older individuals at high cardiovascular risk [15, 16]. A parallel group of PREDIMED divided 447 cognitively healthy adults at high cardiovascular risk (233 women / 214 men, average age 66), into three groups [17]. Some participants were randomly assigned to a Mediterranean Det supplemented with extra virgin olive oil (EVOO, 1 litre a week). The rest were split and assigned either to a Mediterranean diet supplemented with mixed nuts (30g a day, 15 g of walnuts, 7.5 g of hazelnuts, and 7.5 g of almonds), or a control low fat diet.

The study measured the rates of cognitive change over time based on a comprehensive neuropsychological test battery and found the MedDiet supplemented with either EVOO and the nuts had significant benefits on memory (particularly episodic memory), frontal cognition (attention and executive function), as well as on global cognition.

The researchers believed that the beneficial effect of the foods supplemented in the study (EVOO and nuts) on cognition probably stemmed from the abundance of antioxidants and anti-inflammatory agents that these foods provide. It is known that the supplemental foods, EVOO and nuts, are particularly rich in polyphenols [18], known to counteract oxidative processes in the brain, leading to neurodegeneration [19] and to support brain health by means of improved cerebrovascular blood flow and enhanced production of brain-specific repair molecules known as neurotrophic factors [20].

Healthy eating effects on cognitive performance in later life

Based on health data analysis of 16,948 Chinese men and women aged 45-74 from 1993-1998 as part of the Singapore Chinese Health Study we know that there is evidence that adherence to healthy dietary patterns in midlife is associated with a lower risk of cognitive impairment in late life (Wu et al., 2019). This study used adaptations of the Mediterranean dietary pattern as the example for healthy eating. From this data we learn that positive effects are cumulative and can manifest themselves as protection from neurodegenerative diseases affecting several cognitive domains in later life. Therefore, it appears to be the case that it pays to start introducing elements of the Mediterranean diet now, regardless of your age.

Is the Mediterranean diet exclusively plant-based?

Whilst the guidelines for Mediterranean-type diets are that they should include less red meat than Western diets, researchers in Australia tested a variation of this dietary pattern that included meat and also derived cognitive benefits.

Their variation included diverse vegetables, fruits, olive oil, beans, lentils, fish, whole grain cereals, nuts and seeds, dairy products, and low consumption of processed / sugary foods. Participants were asked participants to consume 3 servings of fresh pork per week for 3 weeks or a meat-free diet. Processing speed / reaction time was significantly improved in those who included meat in their diet (Wade et al., 2019). Whilst it is unclear what the mechanism for the benefit might be, what this study confirms is that a Mediterranean Diet doesn’t necessarily need to exclude meat, and that it can indeed derive cognitive benefits even eating red meat 3 times per week. This kind of evidence can give flexitarians more of a reason to mix and match their protein sources, whilst still being certain that the food they’re choosing is “proper brain food”.

Final thoughts

You may think that a whole litre of olive oil per week is a lot, but this includes oil used in cooking and added to salads etc. at the table. The nuts included in the PREDIMED study are equivalent of just a small handful of mixed nuts a day, so both recommendations are doable. Additionally, you may find that it is easier to adhere to a “Mediterranean way of eating” if you can still have foods typically featured in British and other Western diets, such as red meat. So if you are a meat eater, you can be reassured that there are still benefits to be derived from going Mediterranean.

About the author

Miguel Toribio-Mateas is a clinical neuroscientist and nutrition practitioner, currently working towards a professional doctorate in health neuroscience, using health-related quality of life outcome measures alongside biomarkers from microbiome analysis to assess the complex effects of food on cognitive function and mental health via the gut brain axis.

With many thanks to Miguel for this blog. If you have any questions regarding the health topics that have been raised, please don’t hesitate to get in touch with Amanda via e-mail or phone:

amanda@cytoplan.co.uk
01684 310099

Amanda Williams and the Cytoplan Editorial Team

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Last updated on 4th August 2021 by cytoffice