Research has shown that what we eat and drink influences brain functioning, which in turn can affect our mental state and performance 1. Read on to find out how your dietary habits may be affecting your mind-set and functioning at work.
Healthy and Unhealthy Fats
Omega 3 Fats
Omega‑3 polyunsaturated fatty acids are found in cold water fish such as salmon, mackerel, halibut as well as in flaxseeds, pumpkin seeds, walnuts, and their oils. They are normal constituents of cell membranes and are essential for optimal brain function. Since the human body is inefficient in synthesising these fats, we are reliant on the dietary sources listed above. It is recommended that girls and women who might have a baby one day and women who are pregnant or breastfeeding should consume at least 1 portion of oily fish weekly and not exceed 2 portions weekly, while boys, men and women who are not planning on having a baby in the future should consume at least 1 portion of oily fish weekly and not exceed 4 portions oily fish weekly (a portion is about 140g).
Dietary deficiency of omega‑3 fatty acids has been associated with increased risk of attention-deficit disorder, dyslexia, dementia, depression, bipolar disorder and schizophrenia(2)(4)
Why is omega-3 so important for brain health? Research has found that an omega-3 fatty acid called docosahexaenoic acid (DHA) provides nerve cell membranes with “fluidity”- the capacity to transport signals from one nerve cell to another across synapses (5). Synapses are the junctions between nerve cells, and their optimal functioning is central to learning and memory. DHA also provides “plasticity”- the ability of the brain and nervous system to change/adapt structurally and functionally as a result of environmental input; this is required for learning, memory, and in recovering from brain damage (6).
Saturated and Trans Fats
In contrast to the healthy effects of diets that are rich in omega-3 fatty acids, epidemiological studies indicate that diets high in trans and saturated fats adversely affect cognitive performance (7). Trans fats are found in margarine, vegetable shortening, processed foods such as ready-made pies, cakes & cake mixes, biscuits, pizza, crisps, doughnuts, gravy & sauce mixes, artificial creamers and confectionery. Saturated fat is found mostly in meat and dairy products, including butter, as well as some vegetable oils such as coconut and palm oils (tropical oils). The precise mechanism underlying these detrimental cognitive effects induced by high consumption of these fats is not well understood, but it is thought that they negatively affect the fluidity of cell membranes. In addition, it is suggested that they also induce hormonal abnormalities, including the development of insulin resistance (disturbed blood sugar control), and thereby mediate the cognitive deficits associated with high trans and saturated fat consumption (8).
We do need some saturated fats for healthy functioning, but the average man should eat no more than 30g of saturated fat a day and the average woman no more than 20g of saturated fat a day. Trans fats should be kept to an absolute minimum, not exceeding about 5g a day for adults, since unlike saturated fats they have no health benefits whatsoever.
The brain is highly susceptible to oxidative damage because it consumes a large amount of oxygen and thereby generates an abundance of highly reactive molecules known as free radicals (9). Free radicals are unstable molecules which bond with other (stable) molecules in an effort to become stable themselves. In the process, they damage other molecules and trigger a chain reaction of oxidative damage to proteins, cell membranes and genes. The fact that the brain is abundant in polyunsaturated fatty acids (omega-3 fats for example), which are themselves highly susceptible to oxidative damage, compound its vulnerability to oxidative injury. Oxidative damage as a result of free radicals has been connected with ageing and with neurological diseases such as Parkinson´s disease, Alzheimer´s disease, and stroke, all of which detrimentally affect brain function in various ways (10).
To counteract oxidative stress, the body produces an armoury of antioxidants to defend itself. Antioxidants neutralise or ‘mop up’ free radicals that can harm our cells. The body’s ability to produce antioxidants is strongly influenced by genetic makeup (about which we can do nothing) and exposure to environmental factors, such as diet and smoking (about which we can do a lot). Modern lifestyles include more environmental pollution and reduced quality in our diets, such that we are exposed to more free radicals than ever before.
The body’s internal production of antioxidants is not enough to neutralise all the free radicals it is exposed to. Thus, we need to help the body defend itself by increasing dietary intake of antioxidants found in plant foods such as fruits, vegetables, nuts and spices. The compounds in these plant foods interact with and stabilise free radicals, and may thus prevent some of the damage they might otherwise cause, possibly through their antioxidant and anti-inflammatory properties (11-13).Plants synthesise a vast array of secondary chemical compounds which enhance the plant’s ability to survive (14). It is thought that by consuming plants, their antioxidant and anti-inflammatory benefits are conferred onto us. Research has shown that dietary supplements of fruit and vegetable extracts with high antioxidant activity (strawberry, spinach, or blueberry) for 8 months slowed age-related decline in cognitive functioning in animals (15). A subsequent follow-up study showed that these fruit and vegetable extracts also helped reverse the course of neuronal (nerve cell) aging (16).
Some of the highest ranked antioxidant foods are as follows:
Fruits – Blueberries, blackberries, cranberries.
Vegetables – Beans, artichoke hearts, russet potatoes.
Nuts – Pecans, walnuts, hazelnuts.
Spices – Cinnamon, oregano, ground cloves.
From American Chemical Society 2004 (17)
The take home message is to have a minimum of 2 portions of fruit and 3 portions of vegetables daily and to include nuts and spices in your daily diet. In addition, variety is key, as different foods supply a different array of antioxidants. Also, it’s important to steam rather than boil your vegetables, since steaming helps retain more of the antioxidants (18).
Blood Sugar Balance
The importance of balancing blood sugar levels for optimal brain functioning
How you fuel your body is one of the most important choices you make when it comes to brain health and optimal cognitive functioning. Food is turned into glucose or sugar, which is the fuel that drives all cells and bodily processes. Glucose levels must be kept within strict boundaries, since too much is toxic to cells on the one hand, and too little makes us feel tired and lethargic on the other. This balancing process happens through the actions of two hormones. Firstly, insulin stimulates cells to take in glucose when there’s too much of it in the blood- this helps lower high blood sugar levels, but also provides cells with the fuel they need. Secondly, another hormone called glucagon breaks down stored sugar when blood sugar levels are low.
Glucose is the brain’s primary source of fuel. To keep this energy demanding organ functioning at its best, it is critical to maintain steady blood sugar levels so the brain has a steady supply of fuel. Research suggests that even in the absence of diabetes (characterised by impaired blood sugar regulation), those who have poor glucoregulation (the ability to maintain steady blood glucose levels) may suffer from cognitive impairment (19). Tests evaluating working memory (memory which retains and uses a limited amount of information, for a short time, to help solve a problem or perform a task), verbal declarative memory (memory where information is available to conscious recollection) and executive functioning (cognitive processes involved in planning, decision-making, realising tasks, and for recognising and correcting errors) found impaired cognitive functioning among those with poor blood sugar regulation (20).
But why does poor glucoregulation impair cognitive functioning? One suggestion is that elevated levels of blood sugar and the hormone insulin (as a result of a diet high in sugar and refined carbohydrates) may generate high levels of free radicals that can damage cells (21). As discussed above oxidative cell damage has been connected with ageing and neurological diseases which affect brain functioning (22).
How you can maintain steady blood sugar levels
1. Eat breakfast
The meaning of the word “breakfast” is literally “breaking the fast”. Blood sugar levels are low after an overnight fast and will result in an inadequate supply of glucose to the brain and will therefore affect cognitive functioning. How? If your blood sugar levels drop too low, you’ll have trouble concentrating, learning, and remembering information. Research has found that not eating breakfast results in reduced performance on word list recall and memory, but can be reversed by the consumption of a glucose-supplemented drink (23). It appears that breakfast consumption influences cognitive functioning via several mechanisms, including increasing the blood sugar supply to the brain (24). However, it is important to understand that this should not be interpreted to mean you should eat a lot of sweet, sugary foods and highly refined carbohydrate foods (i.e. white pasta, white bread or white rice, as opposed to their whole grain versions) which are rapidly converted to sugar, as these cause detrimental blood sugar roller coasters, which will be described below shortly.
2. Don’t skip meals
This is for the same reason you shouldn’t skip breakfast; it will lead to low blood sugar and insufficient glucose supply to the brain for optimal cognitive functioning.
3. Choose complex carbohydrates
Complex carbohydrates are broken down more slowly into glucose because of their fibre content and therefore provide a steady supply of fuel to brain cells. Complex carbohydrates are found in whole grains, nuts, seeds, legumes, and vegetables.
4. Avoid simple carbohydrates
Simple carbohydrates exist in either a natural or refined form and convert more quickly into glucose than complex carbohydrates, causing rapid blood sugar spikes which can negatively affect cognitive functioning. Because high blood sugar levels are potentially toxic to cells the pancreas releases extra insulin to lower blood sugar levels and restore balance. However, when the pattern of high blood glucose continues, because of a diet high in sugar and refined carbohydrates, the pancreas over-reacts and excessive amounts of insulin are released. Consequently, too much glucose is taken from the blood into the cells, resulting in low blood sugar and subsequent insufficient blood sugar supply to the brain. This rapid drop in blood glucose levels (below the optimal reference range) starves the brain of its primary fuel and we experience symptoms such as energy slumps, cravings for sweets and stimulants (tea, coffee, and cigarettes), irritability, mood swings, poor memory, poor concentration and fuzzy thinking.
Refined carbohydrates are found in white pasta/bread/rice (as opposed to their whole grain versions) and anything containing added sugar like cakes, sweets, ice cream etc. Natural sugars are found in fruit and are better sources of simple carbohydrates because they contain protective antioxidants as well as fibre, which slows down the release of fruit sugar into blood and so reduces blood sugar spikes.
5. Avoid stimulants like cigarettes, coffee, chocolate and soft drinks (including diet soft drinks)
Nicotine in cigarette smoke as well as caffeine in coffee, chocolate and caffeinated soft drinks act as stimulants and lead to increased nerve cell activity in the brain. This in turn results in the release of the hormone adrenaline. Adrenaline is a “fight-or-flight” hormone, biologically evolved to help survival under stressful situations by breaking down stored sugar to heighten alertness and fuel muscles for emergencies. However, unless the extra sugar released in the blood stream is burned off through a physical response as in the “fight-or-flight” reaction in an emergency, blood sugar levels will remain high. This will trigger a large insulin response and lead to low blood sugar levels and subsequent insufficient blood sugar supply to the brain. Usually this results in reaching for another cup of coffee or more chocolate and the blood sugar roller coaster starts over. When stimulants are consumed, blood sugar levels remain high because the “fight-or-flight” reaction has been artificially induced rather than through a genuine emergency and requires no physical “fight-or-flight” response which would use up the extra blood sugar.
6. Make sure you consume protein with each meal and snack
This helps slow down the release of sugar from food into the blood. Choose from chicken and turkey, game, white fish, oily fish (tuna, mackerel, herrings, pilchards, sardines, and salmon), pulses, eggs, yoghurt, cottage cheese, feta, nuts and seeds.
7. Increase your intake of dietary fibre
This slows the rate at which food is digested, slowing the release of glucose into the bloodstream. Choose from whole grains, lentils, pulses, seeds, nuts, fruit and vegetables.
The Mediterranean Diet-The Ideal “CogniSharp Diet”?
Is there an ideal diet which can boost cognitive functioning? Well, in answer to this question, a recent study found that young women following a Mediterranean diet for 10 days had significant improvements in self-reported vigour, alertness, and feelings of contentment as compared to those who continued to consume their normal diets (25). In addition, those in the Mediterranean group had faster reaction times on a task assessing spatial working memory. Participants who followed the Mediterranean diet were required to increase their intake of fruits, vegetables, oily fish, nuts and seeds, and choose low fat dairy products and whole grains. They were also required to exclude red meat, refined sugars, refined flour (refined carbohydrates), pre-packaged and processed foods, caffeinated products, soft drinks and condiments. It is important to note that calorie intake was not restricted.
The research team hypothesised that the benefits they observed were due to increased intake of omega-3 fatty acids (found in cold water fish such as salmon, mackerel, halibut and in flaxseeds, pumpkin seeds, walnuts, and their oils), and magnesium (found in seafood, nuts, dark green vegetables, legumes, whole grain cereals) (26). The results are intriguing, especially considering the short duration of the trial, and suggest that adopting a healthy (and delicious) Mediterranean diet way of eating can enhance mental well-being and functioning.
The Mediterranean diet is really what we have been discussing above- choosing healthy fats and carbohydrates and boosting intake of antioxidants!
1 Westenhoefer J Bellisle F Blundell JE et al (2004) PASSCLAIM–mental state and performance Eur J Nutr 43 Suppl 2 II85-II117
2 Hibbeln J R(1998) Fish consumption and major depression. Lancet 351 1213
3 Horrobin D F (1998) Schizophrenia: the illness that made us human. Med Hypotheses 50 269–288
4 Freeman MP Hibbeln JR Wisner KL et al (2006) Omega‑3 fatty acids: evidence basis for treatment and future research in psychiatry. J Clin Psychiatry 67 1954–1967
5 Gómez-Pinilla F (2008) Brain foods: the effects of nutrients on brain function Nat Rev Neurosci 9 7 568–578
6 Gómez-Pinilla F (2008) Brain foods: the effects of nutrients on brain function Nat Rev Neurosci 9 7 568–578
7 Greenwood CE & Winocur G (2005) High-fat diets, insulin resistance and declining cognitive function. Neurobiol Aging 26 Suppl 1 42–45
8 Greenwood CE & Winocur G (2005) High-fat diets, insulin resistance and declining cognitive function. Neurobiol Aging 26 Suppl 1 42–45
9 Unno K & Hoshino M (2007) Brain Senescence and Neuroprotective Dietary Components Central Nervous System Agents in Medicinal Chemistry 7 109-114
10 Centre for Biomolecular Interactions Bremen (CBIB) (2011) Oxidative damage and antioxidative strategies in brain cells. Last accessed 23.11.11 at http://www.fb2.uni-bremen.de/en/dringen/research?start=1
11 Wang H Cao G Prior R (1996) Total antioxidant capacity of fruits. J Agric Food Chem 44 701–5
12 Joseph JA Shukitt-Hale B Denisova NA (1998) Long-term dietary strawberry, spinach, or vitamin E supplementation retards the onset of age-related neuronal signal-transduction and cognitive behavioral deficits. J Neurosci 18 19 8047-55
13 Joseph JA Shukitt-Hale B Denisova NA (1999) Reversals of age-related declines in neuronal signal transduction, cognitive, and motor behavioral deficits with blueberry, spinach, or strawberry dietary supplementation. J Neurosci 19 18 8114-21
14 Joseph JA Shukitt-Hale B Casadesus G (2005) Reversing the deleterious effects of aging on neuronal communication and behavior: beneficial properties of fruit polyphenolic compounds. Am J Clin Nutr 81 1 Suppl 313S-316S
15 Joseph JA Shukitt-Hale B Denisova NA (1998) Long-term dietary strawberry, spinach, or vitamin E supplementation retards the onset of age-related neuronal signal-transduction and cognitive behavioral deficits. J Neurosci 18 19 8047-55
16 Joseph JA Shukitt-Hale B Denisova NA (1999) Reversals of age-related declines in neuronal signal transduction, cognitive, and motor behavioral deficits with blueberry, spinach, or strawberry dietary supplementation. J Neurosci 19 18 8114-21
17 American Chemical Society (2004) Largest USDA Study Of Food Antioxidants Reveals Best Sources. ScienceDaily.
18 Xu B & Changa SKC (2008) Effect of soaking, boiling, and steaming on total phenolic content and antioxidant activities of cool season food legumes Food Chemistry 1 110 1-13
19 Messier C Tsiakas M Gagnon M Desrochers A Awad N (2003) Effect of age and glucoregulation on cognitive performance. Neurobiol Aging 24 7 985-1003
20 Messier C Tsiakas M Gagnon M Desrochers A Awad N (2003) Effect of age and glucoregulation on cognitive performance. Neurobiol Aging 24 7 985-1003
21 Evans JL Goldfine ID Maddux BA Grodsky GM (2002) Oxidative stress and stress-activated signaling pathways: a unifying hypothesis of type 2 diabetes. Endocr Rev 23 5 599-622
22 Centre for Biomolecular Interactions Bremen (CBIB) (2011) Oxidative damage and antioxidative strategies in brain cells. Last accessed 23.11.11 at http://www.fb2.uni-bremen.de/en/dringen/research?start=1
23 Benton D & Parker PY (1998) Breakfast, blood glucose, and cognition Am J Clin Nutr 67 (suppl) 772S–8S
24 Benton D & Parker PY (1998) Breakfast, blood glucose, and cognition Am J Clin Nutr 67 (suppl) 772S–8S
25 McMillan L Owen L Kras M Scholey A (2010) Behavioural effects of a 10-day Mediterranean diet. Results from a pilot study evaluating mood and cognitive performance. Appetite 56 1143-7
26 McMillan L Owen L Kras M Scholey A (2010) Behavioural effects of a 10-day Mediterranean diet. Results from a pilot study evaluating mood and cognitive performance. Appetite 56 1143-7