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HomeExclusiveEXCLUSIVE: Nutrition and lifestyle for cognitive fitness

EXCLUSIVE: Nutrition and lifestyle for cognitive fitness


Cognitive fitness is a concept that’s becoming increasingly important in today’s world which is characterised with junk foods, mobile devices, and information and sensory overload over the Internet which makes it hard to adapt to fast changing situations, to manage high levels of stress, another hallmark of this age, and to focus and to think clearly as our attention is constantly scattered all over the place.

Ability to adapt to a rapidly changing world, ability to make decisions in dynamic environments, ability to shape and re-shape ourselves to understand and meet the demands of modern world, and ability to still enjoy life, deal with stress and protect our wellbeing… All of these abilities depend on the level of our cognitive skills and fitness. As higher-order thinking processes, cognitive skills allow us to reason, pay attention, learn and remember. Thus, cognitive fitness is crucial for everybody today, particularly for security professionals and medics who work in highly dynamic environments which often require them to make quick and critical decisions under pressure.

In this exercise, we will explore the subject matters of nutrition in Part 1 and lifestyle in Part 2 from a biological perspective, looking at the biochemical processes that are involved in food consumption, exercise, sleep, and stress. And we will try to figure out what we can do to improve our cognitive fitness and our mental and physical wellbeing as a whole, and to reach and enjoy our full potential by understanding how the body actually works.

A sound mind in a sound body

We all know health is a good thing. It’s common sense. Everybody would like to be healthy. However, not everybody would be able to give a positive definition of health when asked. Most people would refer to “not being ill” when they try and define “health” which would be a negative definition. Positive definition, on the other hand, refers to “wholeness, a being whole, sound or well”. We can all infer that being ill takes something from the natural state of a body, thus breaking it, making it less than whole. Nevertheless, understanding concepts such as “health” through its negative is an error of the mind. We must first understand “health” correctly as a concept without referring to its “not being there”.

The concept of “fitness”, on the other hand, is mostly confused with “health”. Confusing “fitness” with “health” is another error of the mind: overlooking the nuances. Yes, fitness is defined as the “condition of being physically strong and healthy”, thus includes “health” but it refers to something else as well, namely “state or quality of being suitable”. This nuance is critical in understanding the concept of “fitness”. “Fitness for what? Which fitness?” would become important questions when the concept is understood in its nuance.

Above, we just made a little exercise for our “cognitive fitness”. The term “cognicioun”, from 15th century English, comes from Latin cognitionem (nominative cognitio) “a getting to know, acquaintance, knowledge”, and it refers to the “ability to comprehend, mental act or process of knowing”. Therefore, it defines our “state of suitability” for the “mental act or process of knowing” or how much we are able to comprehend. If you understand the nuance of fitness and how it differs from the concept of health, you are good to go in terms of cognitive health.

In this exercise, we will explore cognitive fitness from the perspective of health, both physical and psychological, trying to lay out the biological mechanisms which contribute to or deteriorate our state of cognitive fitness by understanding how we are affected by our diet and our lifestyle. We believe, with Spinoza, that “the highest activity a human being can attain is learning for understanding, because to understand is to be free.” The ability to understand what’s at the root of things, the mechanisms of changes and nuances is cognitive fitness. We must learn why we feel the way we feel to achieve this freedom in order to steer our lives in a productive manner and not fall prey to the paralysing power of stress and mental disorders.

We hope, at the end of this exercise, you will be better equipped to tackle life’s challenges with the understanding of underlying mechanisms which will serve as a tool for you to reorganise your lifestyle in a more suitable manner, fit for your body and mind.

Part 1. Nutrition

When it all goes wrong: Too much confusion and comfort

“A sound mind in a sound body”, the English translation of a famous quotation by the pre-Socratic Greek philosopher Thales (Miletus, 624 – 546 BC), refers to the close links between physical exercise, mental equilibrium, and the ability to enjoy life, i.e., to deal with stress and to cope with the challenges of life in a healthy manner. On the other hand, stress is one of the top factors that contribute to cognitive impairment today. A study published in 2022 used the UK Biobank, a large-scale national health and biomedical study with over 500,000 participants, to identify the effects of stress on cognitive function and found “clear links between stress at distinct phases of the lifespan, changes in measures of brain microstructure, impairments in cognitive abilities and negative mental health outcomes”. In other words, the more stress one is exposed to, the more difficult it becomes to have cognitive fitness and to deal with stress.

As the global market of mindfulness and meditation is rapidly growing and is expected to reach nearly £7.5 billion a year by 2027 according to the Australian Centre for Meditation and Mindfulness, stress, anxiety and depression cost the global economy more than £800 billion in lost productivity and the number of stressed people out of 143 countries globally reaches to 35%, according to global statistics.

So why the trends which are marketed to be effective against stress apparently do not work? Michael Poulin, an associate professor of psychology in the UB College of Arts and Sciences, says it’s because mindfulness and meditation, which originated from Eastern cultures, are removed from the context when practiced in Western cultures. Mindfulness practice in Eastern cultures requires one to think of themselves in terms of their relationships and communities, i.e., as an interdependent person. When practiced in the context of Western cultures, on the other hand, it can lead to “selfishness”: “However, for people who tend to view themselves as more independent, mindfulness actually decreased prosocial behaviour,” Dr Poulin says.

“Being present here and now”, which constitutes the attentive process in mindfulness practice, is good, but only when it comes in its own context, “with instructions explaining how to make people think of themselves in terms of their relationships and communities,” researchers say. It should be more about participating in life, in relationships, in the community rather than removing oneself from one’s surroundings. Otherwise, it becomes just another way of isolating oneself from community, by doing so, losing the much-required feeling of support relationships can offer to cope with stress. This is just an example of how a good thing can become a trap if we fail to understand it.

Another confusion is observed in the explanation insulin mechanism, including high blood sugar and insulin resistance which are linked to diabetes. A new study published in June 2023 in The Lancet indicate that more than 1.31 billion people could be living with diabetes by 2050 worldwide. This is of importance to us because studies have shown that high blood glucose levels seen in diabetes can affect the brain’s functional connectivity and brain matter. Diabetes can also cause the brain to atrophy or shrink. “And it can lead to small-vessel disease, which restricts blood flow in the brain, causing cognitive difficulties and, if severe enough, spurring the development of vascular dementia,” researchers say.

The fallacy we often see here is confusing cause and effect. The common explanation is that high blood sugar is caused by insulin resistance. This is an upside-down causality. Here what is represented as the cause – insulin resistance – is actually the result – the effect – of consistently high blood sugar. It is also a “post hoc” fallacy which is Latin, and short for “post hoc ergo propter hoc” which means “after this, therefore because of this”. Put it simply, it is asserting that A is a cause of B just because B occurs after A: They say “insulin resistance is a cause of high blood sugar just because high blood sugar occurs after insulin resistance.” It is another mistake in understanding how insulin works taken out of the context of the actual mechanisms of the body. We must understand how the insulin mechanism actually works to see the great errors committed in this subject which are at the root of the misunderstanding that causes millions of people to suffer from huge consequences such as cognitive decline and disfunction, increased risk of Alzheimer’s Disease, dementia, heart attack and stroke, blindness, painful skin ulcers, loss of lower limbs and kidney problems.

  1. The actual way insulin works and the confusion

Insulin is an anabolic hormone: it is a storage and building up hormone. As an anabolic hormone it “works on target tissues to promote storage of the products of digestion and absorption of a mixed meal.”

In metabolism, which is a biochemical process that allows an organism to live, grow, reproduce, heal, and adapt to its environment, there are two metabolic processes: Anabolism and catabolism. Anabolism refers to the process which builds molecules the body needs, requiring energy for completion, and catabolism refers to the process that breaks down complex molecules into smaller molecules, releasing energy for the organism to use. Anabolic hormones are insulin, oestrogen, testosterone, and growth hormone. Catabolic hormones include adrenaline, cortisol, glucagon, and cytokines.

As an anabolic hormone, every time we put food in our mouth insulin is secreted from beta cells in the islets of Langerhans, which are the regions of the pancreas that contain its endocrine (hormone-producing) cells. This insulin secretion is in response to elevated blood glucose when we eat food. Glucose is one group of carbohydrates known as simple sugars which is the source of energy in cell function. Insulin works as a key to open cells to take glucose inside, thus regulating how much glucose is left in the blood. Blood glucose levels rise every time we eat something, which triggers an insulin response to regulate the glucose levels by either using glucose as a fuel source for cells or storing it as fat for a rainy day.

And there are different insulin responses to three different categories of macronutrients, namely carbohydrates, protein, and fat. Macronutrients are the nutrients we need in larger quantities that provide us with energy while micronutrients are mostly vitamins and minerals. Carbohydrates, which consist of starches, sugars and fibres, trigger the greatest insulin response, except fibres which slow digestion, because they spike blood glucose. Proteins have a moderate insulin response corresponding to the moderate spike in glucose levels and fats trigger virtually zero insulin response. This is because fats don’t break down into glucose when digested. These differing blood glucose spikes and insulin responses are expressed in glycaemic index, “a number from 0 to 100 assigned to a food, with pure glucose arbitrarily given the value of 100, which represents the relative rise in the blood glucose level two hours after consuming that food.” The higher a food’s value is on the glycaemic index, the more it will spike blood glucose, thus resulting with higher levels of insulin which would be quite dangerous both for the body and the brain in the long run.

At the molecular level, cells sense insulin through insulin receptors, but over time when there is too much insulin all the time – when we constantly eat and snack which causes blood glucose levels to rise and in turn causes insulin levels to rise and remain constantly high to counter blood glucose levels – the cells become unresponsive to insulin. Cells find themselves full, unable to use glucose as fuel or store it as fat. Insulin sensitivity decreases and cells become insulin resistant, inhibiting insulin action. Thus, more insulin is secreted to regulate blood glucose levels that remain dangerously high because insulin resistant cells don’t respond to insulin action and remain closed to glucose.

For a 70 kg human, approximately four grams of blood glucose is maintained in the blood plasma at all times. Wasserman (2009) says: “This glucose is critical for normal function in many cell types. In accordance with the importance of these 4 g of glucose, a sophisticated control system is in place to maintain blood glucose constant.” These levels correspond to normal blood glucose levels between 4 to 6 mmol/L before meals and up to 8 mmol/L two hours after eating according to the British Heart Foundation.

High blood glucose over time damages blood vessels that carry oxygen-rich blood to the brain as well as other cells and when the brain receives too little blood, brain cells can die. CDC says: “This is called brain atrophy and can cause problems with memory and thinking and eventually can lead to vascular dementia.” And extremely low blood glucose levels have a similarly damaging effect on the brain as well as other cells.

B. Plenty of food and the detrimental comfort

In fact, this system is critical for survival mechanism. Human survival has always relied on the body’s ability to store energy for starvation periods, to fight off infection and to deal with stress, which are all regulated by the anabolic actions of insulin. And the mobilisation of stored energy when needed relies upon the temporary inhibition of insulin action, in other words insulin resistance. In 1962, James Neel speculated that insulin resistance “must have evolved as an adaptive trait that later turned pathological due to changed lifestyle and diet. He hypothesized that a “thrifty” genotype that helped survival in primitive life characterized by periods of “feast and famine” has now turned detrimental in the modern urban lifestyle and diet.”

In a study published in 2012 that deals with insulin resistance as an adaptive mechanism, the researchers say that “in the current environment, high energy intake, low physical activity, and chronic stress favour the storage of surplus fat in adipose tissue depots that far exceeds their storage capacity and liporegulation.” And this excess in storage capacity, in other words, “lipid overload in central fat depots initiates an inflammatory response” and “activate the mechanism of insulin resistance as would occur in the case of infection or stress.”

Indeed, today, we find very different circumstances from the way of life of hunter-gatherers who had to endure hunger until the next lucky hunt. Now, we live in a state chronic overnutrition, therefore in a state of chronic inflammation. Inflammation is part of the body’s defence mechanism by which “the immune system recognizes and removes harmful and foreign stimuli and begins the healing process.” When we overeat, the excess calories consumed leads to inflammation in in fat cells and “the release of fatty acids into other tissues, including liver and muscles.” On the other hand, excessive intake of sugar and processed foods have been shown to lead to the occurrence and aggravation of inflammation.

Brain is especially sensitive to inflammation. Neuroinflammation is a common feature of almost all central nervous system diseases, and it is also increasingly recognized as a potential mediator of cognitive impairments. Diabetes is at the top of the list of chronic inflammation-mediated diseases and these are ranked as the greatest threat to human health by the World Health Organization (WHO).

In the brain and spinal cord, there are microglia, which act as the first and main form of active immune defence in the central nervous system. These work as the maintenance crew of the nervous system, constantly eating up and cleaning the brain and nervous system from plaques – which are responsible for Alzheimer’s Disease to develop – and any damaged or unnecessary neurons and synapses and infectious agents. Whenever a traumatic brain injury, alcohol, stress, leaky gut or allergies cause inflammation in the brain, these microglia react quickly to decrease inflammation and remove the threat.

There are three mechanisms that destroy the brain: direct toxicity, gut-brain axis and insulin resistance.

Monosodium Glutamate (MSG) is an excitotoxin, a direct toxin for the brain which causes neurons to fire too much until they are completely consumed: “It gives a special taste to processed food which is known as umami in Japanese”. They add this to food to make it taste better than it actually tastes, therefore it is one of the most used food-additives in commercial foods to make you eat more than you would otherwise. Therefore, it is extremely important to read labels when buying food to see if it contains MSG.

Another direct toxin for the brain is mercury found in fish. Nearly all fish and shellfish contain traces of mercury however large, predatory fish (swordfish, shark, king mackerel and tilefish) which live longer accumulate more mercury, so it is recommended to choose smaller fish.

Alcohol is another neurotoxin which contribute to all three of the mechanisms: it is a neurotoxin, it contributes to leaky gut which is increased intestinal permeability, it causes fatty liver and brain shrinkage. It is also important to remember that the brain shrinkage caused by alcohol is dose dependent. The more you drink, the more damage you will suffer.

The gut-brain axis consists of two-way communication between the central and the enteric nervous system which links emotional and cognitive centres of the brain with peripheral intestinal functions and recent studies increasingly show the importance of gut microbiota in influencing these interactions. As such, anything that unbalances the gut microbiota will cause the intestines to be vulnerable to increased permeability. Intestinal permeability is a term describing “the control of material passing from inside the gastrointestinal tract through the cells lining the gut wall, into the rest of the body”. When it is increased, it causes increased brain inflammation.

Insulin resistance, the third mechanism that damages the brain, does so by depriving the brain of glucose, its main energy source – there is another energy source for the brain, namely ketones, but we will discuss those later – when we are on a high-carbohydrate diet. Insulin resistance prevents glucose to enter into cells as we discussed earlier. And even though the brain cells are swimming in glucose, they starve to death because they are not able to use glucose due to insulin resistance.

Sugar is the number one cause of insulin resistance and insulin resistance is the number one cause of cognitive decline over time. Sugar exists in nature in very small quantities, made up of 50 percent glucose and 50 percent fructose, a simple sugar found in many plants which needs to be converted into glucose by the liver. The highest dietary sources of fructose are foods containing white sugar (sucrose), high-fructose corn syrup, agave nectar, honey, molasses, maple syrup, fruit and fruit juices, as these have the highest percentages of fructose (including fructose in sucrose) per serving compared to other common foods. High-fructose corn syrup (HFCS) was first introduced to the food and beverage industry in 1970s principally as a replacement for sucrose because of its sweetness, improved stability and functionality and ease of use. The problem is that almost all sweetened and processed foods now contain high amounts of sugar and HFCS and the liver becomes overwhelmed with the amount of fructose it has to convert into glucose when it also has other critical functions to deliver. Many studies have linked “excessive consumption of HFCS” which is found almost everywhere from fast food items, breakfast cereals, bread and baked goods to sweetened dairy products, canned foods like soups and fruit, and soft drinks, to “health problems like obesity, diabetes and heart disease” as well as non-alcoholic fatty liver disease.

Sugar in itself is perfectly natural, it is found in everything in nature. We are, however, feeding ourselves with too much sugar, amounts which would be impossible to consume if we were to eat only whole foods in contrast to processed foods. Therefore, the overdose of sugar becomes a poison for the brain. With all these contributing factors in mind, we shouldn’t be surprised at how too much food, especially processed food, and the comfort of modern lifestyle result in brain damage that is detrimental for cognitive fitness.

C. Feeding and fasting: Right quality in right quantity at the right time

Nutrition is critical for a healthy brain and cognitive fitness. We have discussed glucose as the only energy source of the brain and we have seen various complications consistently high blood glucose levels create, such as insulin resistance. However, there is another fuel: ketones. Ketone bodies are water-soluble molecules which are produced from fatty acids by the liver during periods of caloric restriction such as fasting when insulin levels are low. The brain gets a portion of its fuel requirements from ketone bodies when glucose is less available than normal: “After strict fasting for 3 days, the brain gets 25% of its energy from ketone bodies. After about 24 days, ketone bodies become the major fuel of the brain, making up to two-thirds of brain fuel consumption.” So, when there is very low intake of carbohydrates which are converted into glucose or no intake of food such as in fasting state, the body turns to ketone bodies to supply its energy by burning fat storage of the body.

Brain only weighs 2% of the body but it consumes 20% of the energy the whole body consumes. As such, it is more vulnerable to the byproducts of the fuel burning with oxygen to make energy. Mitochondria supply cellular energy and maintain control of the cell cycle and cell growth. The way energy is produced is through oxidation. Just like you can’t build a fire without oxygen, you can’t make energy without oxidation. This process produces reactive oxygen species (ROS) which are highly reactive chemicals formed as byproducts of oxidation process. In case of uncontrolled production, ROS “can cause irreversible damage to DNA as they oxidize and modify some cellular components and prevent them from performing their original functions”. In the long run, these oxidants are the hallmark of aging, stroke and neuro-degeneration.

Recent studies have shown that ketones significantly decreased ROS production and the associated excitotoxic changes during energy production process of mitochondria. Other studies found that “very low carbohydrate consumption, even in the short term, can improve memory function in older adults with increased risk for Alzheimer’s disease”. A study which focuses on understanding how diet influences brain aging by looking at brain network stability found that “glucose decreases, and ketones increase the stability of brain networks”.

Although ketogenic diet, which basically consist of mimicking the state of fasting to achieve low blood glucose and insulin levels through a daily consumption of 70 percent fat – since fat causes virtually zero blood glucose spike, – 25 percent protein and only 5 percent or less carbohydrates, has been trending and taken as a fad diet in recent years, it is not new in the medical world. As a comprehensive review states, it was first developed in the 1920s “as a treatment for epilepsy due to early observations of an antiseizure effect”: “Most clinical studies examining the neuroprotective role of ketone bodies have been conducted in patients with Alzheimer’s disease, where brain imaging studies support the notion of enhancing brain energy metabolism with ketones.” As such, “ketone bodies are now thought to be a potential therapeutic strategy in many disorders such as cancer, diabetes, cardiovascular disease, and neurodegeneration.”

No matter what diet you are on, studies suggest that “better cognitive performance, particularly in verbal retention and memory is associated with a higher diet quality,” which supports the “whole diet approach” theory, i.e., a balanced diet as a whole rather than single nutrients is beneficial for brain health which may also include Mediterranean diet, which includes unrefined carbohydrates and starches along with cheese, yogurt, fruits and vegetables with chicken, fish and eggs consumed a few times a week with fat content coming from olive oil, an unsaturated source of fat; the Nordic diet, which includes foods and nutrients such as fruits and vegetables, fish, canola oil, and several types of meat; and the Dietary approach to Stop Hypertension (DASH) diet, which is characterized by low sodium content and small portion sizes.

In light of everything we discussed up until now, this means staying away from too much food, especially junk foods, processed foods and drinks that contain too much sugar, and additives, and going for “whole foods” which include nutrients and healthy drinks such as mineral water. However, when you eat is equally important as what you eat for a healthy brain and cognitive function. We must have understood by now that small frequent meals or snacking in between meals is not a good idea as it causes blood glucose levels to rise and insulin levels to be constantly high, which overwhelms the cells in the long run, leading up to insulin resistance. We must allow some time to the body for the insulin levels to drop. This naturally happens while we sleep during which we consume no food.

Fasting can be extremely beneficial in this context, as one of the best things you can do to reduce insulin resistance, thus improve brain health and cognitive function. Easiest way to start would be skipping breakfast. Marketed as “the most important meal of the day”, breakfast actually had no particular importance attached to it before late 19th century. Before the invention of cereals, breakfast was not a standard or routine meal of the day, let alone being “the most important one”. After Kellogg developed corn flakes in the 1890s, cereals have started to be advertised as health foods even after the coating of cereals with sugar which started in 1940s. Food historian Caroline Yeldham writes that the Romans didn’t eat breakfast and they only consumed only one meal a day around noon. According to Abigail Carroll, it was similar for the native Americans who sometimes fasted for days at a time.

Studies suggest that “intermittent fasting (IF), the abstinence or strong limitation of calories for 12 to 48 h, alternated with periods of regular food intake, has shown promising results on neurobiological health in animal models.” Some studies have found that “IF induces several molecular and cellular adaptations in neurons, which, overall, enhance cellular stress resistance, synaptic plasticity, and neurogenesis.” Intermittent fasting does this by way of production of ketones and increasing growth hormone secretion only by limiting the time frame of eating. Growth hormone (GH) is crucial for the brain as well as for the body as it stimulates growth, cell production and cell regeneration. As another anabolic hormone, growth hormone has a crucial role in both mental and emotional well-being and maintaining a high energy level. It is secreted “as a series of pulses throughout the 24-h cycle” according to the circadian rhythm. In childhood, it promotes growth as its name indicates and in adulthood, it helps to maintain normal body structure and metabolism, “including helping to keep your blood sugar (glucose) levels within a healthy range.”

From an evolutionary perspective, “insulin promotes energy storage in the condition of energy surplus, whereas GH promotes lipid mobilization and oxidation when food is sparse,” thus insulin, which inhibits growth hormone secretion, needs to be low for the growth hormone to be secreted. Therefore, extending the time window of low insulin levels which we naturally experience during a good night’s sleep would help secretion of more growth hormone, thus helping growth hormone to retrieve the fat to maintain and repair the body as well as maintaining, strengthening and building synapses in the brain.

Another benefit of fasting is autophagy, a natural process of the body that removes unnecessary or dysfunctional components, recycling cellular components, thus cleaning up the body through waste management and disposal. The term itself means “self-eating”. Since it cleans up the body, it improves immune system, activates an anti-aging process, enables cells to work more efficiently. Some studies have suggested that increase in autophagy may be related to the improvement of neuronal function. Therefore, fasting is a powerful tool to cleanse the body and the brain, and improve the functioning of the organism as a whole.


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