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Seeing the “light”… or “dark”

Pupillary Responses to Words That Convey a Sense of Brightness or Darkness


Pupillary Responses to Light

It might seem as if we don’t have much voluntary control over the size of our own pupils. Their tiny muscles appear to typify an innate response, mediated by the sympathetic nervous system, with their shape or size pretty much unknown to us. What we can literally see with our own eyes is that we have the ability to decipher a vast range in light intensity, however our pupils may not only respond to these physical changes. New research is revealing their dependence upon cognitive factors, aka, our own thoughts!

We are able to see our way across a dark room to open a curtain and subsequently to make out the clouds of a sunlit sky. The light intensities that we can see, in fact range across 9 orders of magnitude, referred to as the eye’s dynamic range, spanning from the scotopic threshold to the glare limit (minimum and maximum light intensities). These values differ from each other by 1,000,000,000, a value greater than the number of people on Earth.

The light reflex of the pupil is a well-known phenomenon, easily demonstrated by changing the lighting in a room while watching your eyes in the mirror. That simple! The diameter of the pupil can vary between around 2mm to 8mm, allowing simultaneous accommodation of both pupils to light conditions, through dilation or constriction. The pathway through which detection and accommodation occur is well understood. For example, beginning with retinal photoreceptors being stimulated, followed by ganglion cells and pretectal neurons, with stimulation then reaching the nucleus of Edinger-Westphal on both sides. (Felten, O’Banion & Maida, 2016). However, could there be more to this that meets the eye? New research is asking whether it is possible that the mere thought of light or dark could cause this physical change? Laeng & Sulutvedt revolutionized ideas about the nature of pupillary responses in 2014, when they found that pupils constrict when imagining a bright light. The implication of this is that high-level cognitive control can affect our so called “involuntary” reflexes.

Role of Language in Vision

The extent to which language is intertwined with sensory and motor systems is a matter under investigation. Strong theories of embodiment of language specify that understanding language relies on mental simulation. For example, comprehension of the word cat involves forming of a mental picture of this animal. Weak embodiment theories and traditional views give less emphasis to the importance of simulation. Embodied theories predict that word meaning alone can trigger brain activity associated with the simulation and therefore also accompanying actions. In alignment with this view, the paper to be explored in this article, Mathôt et al (2017), hypothesized that word meaning alone could trigger this ‘reflex’ response of the pupils, tying together the ideas of embodiment of language and of high-level cognitive control of pupillary response. If comprehending words related to brightness or darkness activates brain areas involved in processing these concepts, then pupillary responses could be triggered in the same way as if these stimuli were imagined or actually attended to.

Experimental Design

First, a group participants were presented with a sequence of words and asked to rate brightness and valence of these in separate blocks. Words were therefore rated on two scales of one to five, ranging from negative to positive and bright to dark. Categories of words were therefore produced, for example, those related to brightness or those with negative connotations.

Control Experiment                                         Main Experiment

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The experiment aimed to compare responses to the sets of words associated with brightness to those related to darkness. Therefore, accurate matching for characteristics other than semantic meaning was needed for words in the two categories. The frequencies with which each word occurs in books was matched for this purpose, as was the total presented luminance of the words in each category for the visual task, for example through choice of words with similar numbers of letters and alterations to font size etc.

There were two main experiments carried out, in order to test both auditory and visual word comprehension. Words were therefore presented either in black writing, or in a synthetic voice. The level of brightness conveyed by the word (semantic brightness) varied, each falling in one of four categories: conveying brightness, neutral, conveying darkness or animal names.  A control experiment was also carried out in which words did not vary in their association to brightness or darkness, but in terms of valence.

Overall, 86 participants took part in the experiments, with roughly 30 in each of the visual, auditory and control tasks. A video-based eye tracker recorded pupil diameter as a proportion of the size at word onset. Initially a central fixation dot would be displayed for three seconds, followed by the presentation of a word for the same length of time, each in a random order. Participants were informed that the task was to press the space bar whenever they heard or saw an animal name.

Results and Evaluation

For visually presented words, dilation occurred around 600 ms after presentation of the word followed by constriction, regardless of semantic meaning (see figure 1), due to the visual stimulation. The time following this expected response holds the key to addressing the experimental hypothesis.

Figure 1

Figure from Mathôt et al (2017). Graph of change in pupil size with time following word presentation. Visual experiment results are displayed in a) and auditory results in b). Vertical dotted lines represent mean response time to animal names. Shaded areas show ± 1 standard error. Horizontal lines indicate times when pupil size differed between bright and dark word categories at each of the significance levels shown.

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Overall, results confirmed that participants’ pupils were smaller when presented with a word conveying brightness and larger when processing a word associated with darkness (see figure 1). From a default, Bayesian one-sided, independent-samples t test, the Bayes factor was found to be 6.7 for the visual task and 3.8 for auditory presentation, giving a combined Bayes factor of 25.4, strongly supporting the hypothesis. The greatest changes in pupil diameter were observed between 1-2 seconds after the word first appeared, with time delay being slightly shorter for auditory presentation (see figure 2).

Figure 2

From Mathôt et al. (2017). Graphs of the magnitude of difference (pupil size for words conveying darkness minus size that for words conveying brightness) of individual participants for the a) visual experiment and b) auditory experiment. Graphs of change in pupil size over the 1-2 second window from time of word onset, presented for each word for the c) visual experiment and d) auditory experiment. Bars all show ± 1 standard error.

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A follow up analysis examined the trend in pupil response over smaller time intervals. A linear-mixed effects model, was generated, using ‘pupil size’ as the ‘dependent variable’ and ‘semantic brightness’ as the ‘fixed effect’. This was carried out for each 10 ms window following word presentation, finding the effect to be reliable from 1,310 to 2,410 and 2,440 to 2,760 ms for the visual task and 1,030 to 1,360 ms in the auditory task. Further support for the general effect on pupil size across the sample was found through a Bayesian one-sided, one-sample t test.

The correlation found between valence and semantic brightness also needed to be addressed, as words associated with brightness are rated more positively and vice versa. As this correlation was so strong, a control task was necessary to confirm that no pupillary response was correlated with valence. Statistical tests confirmed a strong correlation between emotional intensity and pupil size, however, whether the word was positive or negative was unimportant. Therefore, only the absolute magnitude of the emotional intensity correlated with pupil size, meaning valence could not be responsible for the trend observed. However, it would not be entirely valid to ignore this correlation when interpreting the results as a weak correlation was found between words conveying brightness and higher emotional intensity. Regression analysis was used in order to account for this, with emotional intensity as control predictor, still finding brightness to be significant in its effect on pupil diameter.

A key strength of this study was the use of much larger sample sizes than in related experiments. This was a precaution taken due to the expectation of only small changes in pupillary response being observed. Only words associated with brightness or darkness were included in the final statistical analysis. The validity of results was, however, confirmed through finding similar outcomes when all words were included. The use of a variety of statistical techniques is also an important strength of this study. Through the controls and analyses listed, it is possible to reliably determine that the observed effects were not due to valence and emotional intensity of the words, but that brightness level was significant.

However, there were several limitations to this study, for example there was no consideration of cross-cultural or language differences, as all words were presented in French to French speaking participants. Further to this, several words used in the trials were extremely semantically similar, meaning variation was limited, as a high degree of matching between categories was prioritized by experimenters. The age of participants was also not considered as a separate factor, with an age range of 18-54 included in the visual experiments and 18-31 in the auditory tasks. It is known that the maximum dilation of the pupil tends to decline with age, so this may have been a worthwhile consideration.

Further limitations exist at a wider scale, beyond this single study. For example, the theory of embodiment of language is potentially a subject of selective reporting and publication bias. The scale of studies demonstrating embodied-cognition is also fairly limited and further replication would help increase reliability.

Discussion and Conclusion

A key starting point of this study was the idea that language comprehension is associated with the formation of sensory representations, similar to those arising when the concept or object of the word is itself attended. This would rely on involvement of brain areas unrelated to linguistic processing and instead related to visual information. The ability to trigger responses associated with these words, such as pupillary changes is therefore logical. This is the first time word meaning has been demonstrated to be sufficient to generate these effects.

Our use for these mechanisms is largely unknown and there is a potential that they are simply byproducts of comprehending language. It is, however, interesting to speculate what the functionality might be. The authors of this study recognize that these physiological changes could have aided word comprehension. This is because, occurring 1-2 seconds after presentation, responses would be too slow to be beneficial.

It seems that the responses triggered in this experiment were irrelevant to the task, so it is uncertain what other function they could serve. One possibility is that embodied language and consequent responses can be beneficial preparing the body for following conditions, in this case, light intensity changes.

A further discovery has come to light this year, related to the complex and predictive nature of the pupillary response in a different context. Zavagno et al. (2017) monitored pupil diameters while participants observed static or dynamic images of grey-scale gradients. These results suggested that pupil constrictions occurred in anticipation of brightness increases, protecting from damage and pain. Anticipatory dilation in response to expectation of darkness can also be argued to be an advantageous feature, due to shortening the time taken for adaptation to occur, potentially offering an ultimate evolutionary explanation, rather than proximate mechanism for the pupillary results observed in the Mathôt et al. study.

Overall, previous results have demonstrated the relationship between higher-level cognition and pupillary responses. There is also building evidence to support the idea that language comprehension involves generation of simulations. The combination of these two ideas has been shown through the demonstration that pupillary reflexes are triggered in response to word presentation alone, suggesting a tighter link between bodily responses and language than is commonly understood. Whether this is a functionally useful property of our sensory system is unknown, but there is some research to suggest it serves an advantageous anticipatory role.


Felten, D. L., O’Banion, M. K., Maida, M. E. (2016). Netter’s Atlas of Neuroscience (Third Edition). (pages 353-389). Ney York: Elsevier inc.

Laeng, B., & Sulutvedt, U. (2014). The eye pupil adjusts to imaginary light. Psychological Science, 25, 188–197.

Mathôt, S., Grainger, J., Strijkers, K. (2017). Pupillary Responses to Words That Convey a Sense of Brightness or Darkness. Psychological Science, 28(8) 1116–1124.

Zavagno, D., Tommasi, L., Laeng, B. (2017). The Eye Pupil’s Response to Static and Dynamic Illusions of Luminosity and Darkness. i-Perception, 11;8(4).


Natural Knack for Numbers

In Oliver Sacks’ book ‘The Man Who Mistook His Wife for a Hat’ he describes the behaviour of two twins, John and Michael, who had been previously diagnosed as “autistic, psychotic and severely retarded”. What he observed in them, on the other hand, was closer to genius. Their mathematical abilities were so outstanding and unusual that they still provoke questions about our own innate mathematical ability.

Completely incapable of performing simple addition or subtraction, and lacking any concept of multiplication or division, these twins had an extraordinary ability to ‘feel’ or ‘see’ numbers. For example, Sacks recalls an occasion in which both twins said the number 111 aloud when a box of matches fell to the floor. On counting, it was realised that this number had been present in the box. The twins even repeated ‘37’ three times, showing recognition of this as a factor, despite their inability to perform any calculations.

The abilities of the twins also extended to other areas of maths, for example, listing prime numbers of twenty figures or telling the week day of any given date!

This is clearly unusual. For most people, using maths in everyday life is somewhat of a bugbear. Even figuring out the date of next Wednesday can cause a mild headache, let alone a date years into the future. However, we do have some mathematical capability that is seemingly not learnt through school. Children as young as five months have been shown to have an understanding of addition (study by Karen Wynn, University of Arizona). This experiment also relied on attention-grabbing Mickey Mouse dolls, as babies are not exactly known for their mathematical interest. The innate ability to see numbers is known as subitization, but, for most of us, applies only to embarrassingly small quantities.


A further way of learning about mathematical understanding comes from cultural studies. I can’t remember the day on which the chanting of times tables began. Having been drilled into my head so early, since so far back in childhood, I can’t imagine a life without these concepts. For all I know, they could have always been sitting there in my mind, a natural thinking process.

Through studying societies where education and language differ, we can reveal surprising truths about our own abilities and how they arise:
Do we rely on language for mathematical thinking?
Do we have the ability to see numbers?
What about numerical patterns?
Or geometry?

The Mundurukú are an Amazonian tribe, living an isolated life in the forest with a rich culture, full of traditions. Their terminology for numbers is extremely limited, only reaching up to 5, with even some of these words appearing to translate to rough estimates, such as four-ish. So how does this affect their lifestyle and understanding? It’s easy to think of language and arithmetic as separate capabilities and people often consider themselves talented at one but not the other, however we rarely think about the way in which they interact. We now understand that human babies and other animals use this rough estimation of numbers, named ‘analogue representation’, rather than exact counting, which is only demonstrated by older humans. For example, when Pica showed Mundurukú individuals different numbers of dots on a screen, their answers were wildly different from those given in the west, for example the number 5 was identified only 28% of the time. It is the innate number recognition ability, differing from our counting system, that is reflected in the Mundurukú language.

Pica himself also provides a fascinating case study of the way in which numerical language can influence culture. On returning from his studies of the tribe he experienced extreme culture shock, having lost track of numerical concepts, causing great problems with timekeeping, among other things.

A further study of this same tribe has revealed findings related to geometry; a concept completely absent from their language. The study, however, found that their ability matched that of US children, suggesting that understanding images such as right angles and equilateral triangles was unaffected by language. Geometric understanding therefore seems to extend more widely across cultures, being less dependent on language. Other studies have also found that young children and tribes have a greater ability to recognise ratios and plot logarithmic scales, than carry out stepwise counting in the way we are accustomed to.

These results may be interpreted from an evolutionary perspective. In the natural environment, we perhaps rely on recognising ratios and rough estimations of numbers. This allows us to, at a flash, recognise which patch of berries it might be more profitable for us to collect etc. An understanding of geometry can be highly beneficial in navigation and other activities. Our style of numeracy, on the other hand, does not have a place in this lifestyle. It is only in modern routines, where exact counting of minutes, pennies or G&Ts has become a necessity.

The Man Who Mistook His Wife for a Hat
Alex’s Adventures in Numberland


Blue Zones – Healthy, Happy and Spreading

Live to 100, stay healthy and skip the meds! Dan Buettner has led research into the five locations where people around the world live longest, remaining healthy:
-Sardinia, Italy
-Okinawa, Japan
-Loma Linda, California
-Nicoya Peninsula, Costa Rica
-Ikaria, Greece


What secrets can be learnt from these 5 ‘Blue Zones’ with the longest lived residents? Could studying these locations have revealed any keys to extending life expectancy?
Teams of researchers have investigated common factors shared among these residents in search for possible answers. The lifestyle factors that have been highlighted are referred to as the ‘Power 9’:

Well who would have guessed? Although it is in no way surprising that exercise is good for your health, it is interesting to note that high intensity exercise rarely features in the daily lives of these individuals. Their exercise is incorporated into daily routines, often in an enjoyable way and as a necessity. This is exercise in a style far different from a rushed gym session which may often be considered to make up for an otherwise sedentary day.

2.Fullness vs satisfaction
Sopping eating when nearing fullness is a practise encouraged in many diets for weight loss. This practice appears to be commonly followed in these locations, being partially responsible for maintenance of a healthy weight. The Okinawan mantra ‘Hara hachi bu’ captures this tradition precisely, reminding them to stop eating when feeling only 80% full. It seems that culture here is a huge factor promoting healthy dietary habits.
A further unusual routine shared among these locations is to eat the smallest and final meal of the day in the afternoon or early evening, therefore leaving an extended period of fasting overnight compared to most societies. Intermittent fasting has recently received a large amount of both research and media attention. Several studies have linked this to preventing and reversing obesity, as well as related metabolic issues. For example, a paper published in Cell Metabolism 2014 reported that fasting for at least 12 hours in mice resulted in them remaining healthier and lower in weight than others, despite their calorie intake remaining the same. The optimal way to practice of intermittent fasting is still under debate, for example low calorie days vs overnight fasts. Evidence also exists to suggest that to boost the benefits, fasting should be combined with high intensity exercise on an empty stomach.

3.Fresh and fibrous
The majority of these individual’s diets consist of fresh fruit, veg and wholegrains. Beans and nuts are also regularly eaten as a protein source, with meat and fish only being consumed in moderation in most areas. Residents of Loma Linda, however, are pescetarian, avoiding meat all together. Nuts are a popular snack, adding a wide variety of vitamins and minerals to the diet.

4.Dine with wine!
Opinions on the relationship between alcohol and health seem to swing almost daily in the media, largely fuelled by the intense interest among readers.

“Half a glass of wine a day ‘can increase breast cancer risk’”
“drinking tequila is good for your bones, science says”
“drinking wine engages more of your brain than solving maths problems”
“drinking a pint of beer a day linked to reduced risk of a heart attack”

People’s relationship with alcohol in the Blue Zones is far different from that in many societies, however this gives us no reason to encourage abstinence. In four of these locations, alcohol is regularly consumed in moderation, for example 1-2 glasses of wine per day. In Sardinia the preference is for cannonau wine, which is high in antioxidants and polyphenols which are known to be preventative of many diseases.

5.Tackling Stress
Although stress may be inevitable in any life circumstances, an important feature of lives within Blue Zones is routine practices to reduce stress, for example, happy hour in Sardinia, napping in Ikaria and preying in Loma Linda by seventh day Adventists. Chronic stress is associated with many inflammatory diseases and is therefore linked to many of the problems experienced in old age.

6.Family Time
Forming close relationships with loved ones is an essential part of life in these locations. This comes in many forms, such as commitment to a single partner, love and care for children and also valuing aging relatives. Older members of the family are, in general, respected and looked after within the family home. Other studies have separately investigated the effects of social structure on mortality. For example, a paper published in the Journal of Health and Social Behaviour found a lower likelihood of death among individuals with social ties with relatives, friends and the community. This can even be as simple as the influence of loved ones in promoting healthy behaviours, such as eating habits or quitting smoking etc.

In these areas 258 out of 263 centenarians belong to a community of shared faith. Membership in these communities involves attendance of services and other activities which help promote a sense of belonging. The association between sense of community-belonging and health has also been noted in other studies, such as of self-reported health in Canadian citizens in 2002.

“Ikigai” in Okinawa and “plan de vida” are both terms used to describe a person’s reason for waking up. In 2014 a study was led by UCL of 9050 people in England, measuring eudemonic wellbeing (related to sense of purpose and meaning in life). A key finding was that eudemonic wellbeing is associated with increased survival. 29.3% of people in the lowest wellbeing quartile died during the study period, compared to 9.3% of the highest quartile. It is estimated that those with highest eudemonic wellbeing live an average of 2 years longer. Sense of purpose has often been highlighted as important to happiness, which is further associated with lower risk of death. Just having a reason for living is therefore implicated in increasing life expectancy.

9.Positive Influence
Healthy habits are contagious. Carrying out these dietary and exercise routines, as well as holding these values is simply part of the culture in certain social groups. Close friendships within these societies are an encouragement to continue with these life-lengthening customs.

Lifestyles in each of these zones revolve around simplicity, compared to modern standards. The stress and rush of modern lifestyles, leaving little time for exercise and, quite literally, a need for “fast” food, might be inevitable in most societies, but also responsible for all kinds of chronic illnesses with which they are plagued.

The Blue Zones Project
The findings of the Blue Zones research is now being applied to help new communities adopt healthier behaviours and live longer. Taking inspiration from these healthy and happy areas, the project aims to make changes to the environment which will encourage residents to live out more of these 9 practices.
Policies have been transformed, such as encouraging dietary changes and preventing smoking. The food available to the community, from restaurants and supermarkets has also been altered in accordance with the recommendations made from the original Blue Zones. Infrastructure changes have also been made to public spaces and homes to encourage people to exercise more and eat less. The formation of strong relationships, sense of community, finding purpose and stress management are also key to these schemes.

For example, the Blue Zones Project has already begun in three communities of Southern California: Redondo Beach, Hermosa Beach and Manhattan Beach. Within two years, a 14% decrease in obesity and 30% decrease in smoking was already apparent. Exercise has also been on the increase, for example through the organisation of morning activities and walking school busses in Manhattan Beach community.

The main findings of Dan Buettner’s research is detailed in several books, such as ‘The Blue Zones’, ‘The Blue Zone Solution’ and ‘Thrive’.

References and Further Reading:
World – Stamp by

Save Our Sleep

Considering that we spend 1/3 of our lives asleep, we give it very little thought. The importance of sleep is regularly overlooked from day to day and not given the same attention as, for example, our diet and exercise plans. Sleep patterns changed massively with the invention of electric lights, and have only worsened since, as technology allows 24-hour communications. It is not exactly surprising that this sleep deprivation has been found to have many negative consequences.

Facts about sleep

o Our liver, heart, pancreas, kidneys and lungs are all able to create their own circadian rhythms, independent of the brain. Altering meal times and exposure to light can cause these factors to be out of sync with each other.

o Humans sleep around 3 hours less per night than most primates.

o The shift to daylight saving time in spring (causing one hour less sleep) results in nearly 20% more road accidents on the following Monday.

o 40-70% of alcoholics suffer from insomnia.

o Twice as many people are killed or injured by drowsy-driving as are by driving accidents related to drugs.

o After 24 hours without sleep, performance is impaired so much that levels fall to those of a drunk person (blood alcohol greater than 0.08%).

o When we are awake, adenosine builds up, causing us to feel drowsy after a long period without sleep. Caffeine blocks the adenosine receptors in the central nervous system as well as increasing the heart rate.

o It takes around 5 hours for half of the caffeine in our body to be metabolised (the half life). The way we respond to caffeine varies between individuals due to differences such as in the adenosine A2A receptor gene, altering the level of sleep disruption caused.

o Our circadian clock creates an almost 24 hour rhythm which causes us to feel tired at almost the same time each day. We rely on environmental cues, such as light, to reset this every day because it may be a little under or over 24 hours. It is therefore very common for blind people to suffer from non 24-hour sleep-wake disorder, going through phases of good and bad sleep as their rhythm moves in and out of sync with day and night times.

Stages of Sleep

In 1928, the electroencephalogram (EEG) was first used, allowing the study of voltage changes in the brain. These changes are caused by neurone signals and therefore it became possible to track brain activity. Studying this has given us a much greater insight into what happens during sleep.
Sleep occurs in different stages, that take place in a set order (the sleep cycle). This cycle takes around 90 minutes and is then repeated. It consists of non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). There are 4 stages of NREM sleep, during which conscious awareness of our surroundings disappears and, in the final 2 stages, we may begin dreaming. Activities such as walking and talking also can occur in the final 2 stages of this NREM sleep. This takes around 70 minutes and then REM sleep takes place, involving similar patterns of brain activity to being awake. Dreaming within this phase of sleep is likely to be more vivid and complex.

Importance of Sleep

The initial reason why sleep was evolutionary favourable is unknown. There are 3 main theories to explain this:
-> for cellular restoration
-> for energy conservation
-> for memory consolidation

Whatever advantages sleep initially brought to animals, we now understand that sleep has a great many benefits.

The National Sleep Foundation recommend adults sleep for 7-9 hours per night. It is fairly well agreed that around 8 hours of sleep are required for an adult, and between 9-10 hours for a teenager. the National Health Interview Survey found that from 2005-2007, nearly 30% of adults had 6 hours or less sleep per day.

This sleep deprivation is worrying as it is associated with many health problems:

-Cardiovascular Disease
The reason why sleep deficiency increases the risk of CVD is unknown, but there are several possibilities. Metabolic changes occur during sleep which could mean that a deficiency increases the level of fat in the blood and platelets are most able to form clots throughout the nighttime. The endothelial cells of blood vessels, hormone levels, heart rate and cytokine production are also affected by sleep.

During sleep, our blood sugar level is maintained at a constant level. When we are awake throughout the night, this level will fall and this affects our insulin sensitivity. Studies have shown that after sleep deprivation, insulin is less effective at lowering blood glucose. there are other factors linking sleep and diabetes as well, such as an increased carbohydrate intake.

-Anxiety, depression and other mental health
There is a strong link between sleep deprivation and poor mental health, with either one being a risk factor for the other. For example, 80% of people with depression or schizophrenia have sleep problems. It has also been suggested that having a history of insomnia increases the risk of depression by 4 times. The way in which sleep affects mental health is not fully understood but it is known to bring about several hormonal changes which could play a part.

-Decreased cognitive performance, memory and decision making
Through the use of EEG, it has been observed that often during sleep, the same neural activity is repeated as took place when awake. This may indicate the formation of memory by replaying the day’s events. Many studies have also found memory to be better in subjects allowed a greater number of hours asleep.
The link between sleep and cognitive performance is particularly noticeable in adolescents, who experience a 2-3 hour difference in circadian rhythm compared to adults, which occurs naturally. This is not a result of using technology throughout the night, even though this can worsen sleep patterns. This means that an adolescent waking up at 6 or 7 am is equivalent to an adult waking up at 3 or 4 am.
A US study showed that delaying the start of school by 1 hour reduced the number of road accidents in 17-18 year olds by 16.5%. The same study found (as lots of others have) that there was a positive correlation between numbers of hours slept and grades achieved by the individuals. By moving the school start time forward, many people expected the bedtimes of students to become later, however they remained constant throughout the experiment, resulting in longer nights of sleep.

-Weight Gain
It has been shown that after sleep deprivation, appetite will increase due to hormone changes. This comes with a particular craving for carbohydrates. The hormone Leptin is produced by fat cells in the body and causes us to feel satisfied, where as Ghrelin is mainly produced by the stomach to stimulate appetite. When deprived of sleep, our leptin production is reduced as well as our Ghrelin production being increased. Eating at night is also dangerous for dieters as it has been shown that the amount of insulin, glucose and fat in the blood will be at completely different levels depending on whether a meal is eaten during the day or night.

-Poor immune response
In 2002, a study in the Journal of the American Medical Association gave 2 groups of subjects an influenza immunisation. One group had slept for 4 hours and the other for 8 hours. The findings were that the group with less sleep had produces less than half of the amount of antibody as the other group. A 2012 study also observed the number of white blood cells decreasing throughout 29 hours of being awake.

-Types of cancer
The link between cancer and lack of sleep could be attributed to changes to hormone levels, reduced melatonin levels, reduced immune function or disruption of the cell cycle. Whatever the cause, there is evidence that a link does exist. Shift workers with extreme disruption of their circadian rhythm have been found to have a 50% greater risk of breast or prostate cancer. Links have also been found with other types of cancer and the risk varies with the level of sleep disruption.

Sources Used:
Journal of Clinical Sleep Medicine
National Sleep Foundation
The National Sleep Research Project
Sleep – A Very Short Introduction (Oxford University Press)
Centre for Disease Control and Prevention
The Better Sleep Council
American Psychological Association
Science Direct: The Metabolic Consequences of Sleep Deprivation
Journal of Applied Physiology – Sleep Loss: A novel risk factor for insulin resistance and Type 2 diabetes
Principles and Practise of Sleep Medicine sample
ScienceDaily: sleep deprivation effect on the immune system mirrors physical stress
National Institutes of Health
Harvard Health Publications
Cancer Treatment Centres of America

Vital for Vegetarians

In 1989, a poll found that 3% of the UK’s population was vegetarian. This figure has recently been estimated to be 5.7%. There are, of course, many ethical and environmental reasons to choose a plant-based diet, however, there is debate surrounding the health implications. Is eating meat good for us or are we better off without it? This article considers recent research concerning vegetarian’s health, leaving aside any ethical debate. Is the vegetarian diet the best option for our health and how can common deficiencies be avoided?

There are many statistics that are commonly quoted in favour of vegetarianism. For example, vegetarians have:
Lower cholesterol (LDL) and blood pressure
Lower risk of cancer
Lower risk of type-2 diabetes
Average life expectancy of 9.5 years longer for men and 6.1 years for women
Lower average BMI
Lower obesity rates (16.7% compared to 33.3% for meat eaters)
Lower rate of food allergy development

The BBC’s recent programme ‘How To Stay Young’, follows this line of research. The study of Loma Linda is discussed, highlighting that people here ‘live up to 10 years longer than the average Californian’. Within this town, the main religion encourages vegetarianism and a high proportion of the population is vegan. A questionnaire carried out here also found the vegan diet to be associated with the best overall health, and mortality being reduced by one quarter.

However, vegetarians also generally have a higher level of education, exercise more regularly and are less likely to smoke or drink alcohol excessively. This data has repeatedly been found by studies, for example the American Journal of Clinical Nutrition 2009, and the Journal of American Diet Association. This means that it is difficult to establish a causal relationship between the correlations found between improved health and vegetarianism.

The difficulty of drawing conclusions from this data is demonstrated by the 1996 BMJ study of 11000 health conscious individuals. These people were recruited from health food shops, vegetarian societies and magazines. The group had a mortality rate around half of that of the general population. Within the group, 43% of the subjects were vegetarian, and they were not found to have any significant differences in mortality. It appears that intervention studies would provide clearer health advice than observational studies when assessing the impacts of a vegetarian diet. However, this sort of data is not easy to come by.

Following a vegan or vegetarian diet also increases the risk of several deficiencies. There are ways to avoid these, but this often requires a fair amount of planning that would not need to cross the minds of meat eaters.

Vitamin B12
Deficiency of vitamin B12 is fairly rare amongst meat eaters (only 5%), compared to 68% of vegetarians and 83% of vegans. This is because vitamin B12 is found only in animal-based products, such as meat, fish, eggs and dairy. This means that in a vegan diet this vitamin must be obtained through dietary supplements.
Deficiency is not to be taken lightly, as it can cause anaemia and nervous system damage. Common symptoms include low energy levels, tingling, numbness, blurred vision, confusion and poor memory.

This is an amino acid that is found exclusively in meat and fish. It is not an essential amino acid as it can be manufactured by the liver, however, around half of the body’s creatine is obtained from the diet. The synthesis of creatine also requires several dietary substances, including vitamin B6 and B12., which are generally lacking in a vegetarian diet. Creatine is necessary for muscle energy and nervous system function. A deficiency of creatine is not common, however, lower levels are generally found in vegetarians with could still be detrimental. Increasing levels of creatine have, for example, been found to be associated with memory improvement (2010 British Journal of Nutrition). Creatine can also be taken as a supplement, which may therefore be advisable for many vegetarians.

This is a dipeptide formed from beta-alanine and histidine. When carnonise is eaten it is digested by enzymes into these two amino acids. Therefore, the body must produce its own carnosine using the building blocks. Beta-alanine is found in meat and fish, so is usually lacking in vegetarians. Carnosine is a popular supplement against ageing as it protects against several of these processes. Carnosine is mainly found in our muscles and is known to improve their performance. Dietary supplements of Beta-alanine have been shown to be the most effective way of increasing carbonise in the body.

Vitamin D3
Vitamin D deficiency is extremely common amongst both omnivores and vegetarians. The most common dietary sources are meat, fish and eggs, however even eating large amounts of these foods may not be satisfactory. The National Health and Nutrition Examination Survey found 45% of the US population to be deficient between 1988 and 1994, whereas 77% were found to be deficient 10 years later. Statistics on vitamin D deficiency are usually based on a level of 10ng/ml in the blood, whereas several studies have found 30ng/ml to be an optimum level for health. By these standards, 90% of the UK population would be deficient throughout the winter. There are two main types of vitamin D in the diet. These are vitamin D2 (which is found in plant-based foods) ad vitamin D3 (which is found in animal products). These two types of the vitamin are metabolised very differently in the body and a study published in the American Journal of Nutrition very clearly stresses the advantages of D3 over D2. There are, however, vegetarian vitamin D3 supplements available and the body naturally synthesises vitamin D3 when exposed to sunlight. Since over 90% of our vitamin D should be produced due to sunlight anyway, the dietary factors are less significant. The risk for everyone in the population is high, not only vegetarians.

This is an omega-3 fatty acid which is found in animal products, especially in fish. It is used throughout the body as a structural fat, such as in the brain, eyes and heart. 30% of the structural fat in the grey matter of the brain consists of DHA, and it is thought to be important in the development and maintenance of the brain.
It is possible for the body to manufacture DHA from a different omega-3 (ALA). ALA can be easily consumed as part of a vegetarian diet, as it is found in flaxseeds, chia seeds and walnuts. The trouble here is that the body is not very efficient at this conversion and so lower levels are usually found in the blood plasma of vegetarians and vegans. Lower levels are also found in the breast milk of vegan mothers, however, the impact of this on infants is unclear. Vegan sources of DHA are available in the form of supplements made from algae. It is therefore easily possible to avoid deficiency whilst following a plant based diet.

Iron deficiency is the most common deficiency across the world. It is estimated that 30% of the total population are anaemic and this figure varies hugely between different groups. For example, menstruating and pregnant women have larger daily requirements of iron, causing higher incidence of deficiency. 8.7mg or iron are required daily for men, compared to 14.8 for women. The average daily intake of iron from food sources is 16.3–18.2 mg/day in men and only 12.6–13.5 mg/in women.
Vegetarians generally do not have higher rates of anaemia than average, but this is likely to be due to other lifestyle differences. Following a vegetarian diet significantly reduces the number of iron sources available, so paying more attention to iron consumption is important.
There are 2 main types of iron: heme-iron and non-heme iron. Heme-iron is found in meat, and is readily absorbed into the body. Non-heme iron (unfortunately for vegetarians) is less easily absorbed, and is more easily absorbed in the presence of heme-iron. Despite this, it is possible for a vegetarian to consume an adequate amount of iron, without supplementation.
Good sources of non-heme iron include:

*many other herbs also contain large amounts of iron

Sulphur is mainly found in animal based foods, and is a necessary component of 4 amino acids. Meat and fish are described as ‘complete’ protein sources because they contain all 9 essential amino acids (including methionine which contains sulphur). With these 9 amino acids, the body is capable of synthesising any other amino acid we need.
The sulphur that we need to manufacture amino acids in our bodies is mainly obtained from protein in our diets, and vegetarians are at higher risk of sulphur deficiency. Sufficient sulphur can easily be found in a vegan diet in the form of legumes, soy products, nuts, seeds and grains. Processing of foods can, however, reduce sulphur content, as can growing crops in sulphur deficient soils.

Sources used:
PubMed (Vegetarian diets: what do we know of their effects on common chronic diseases)
BMJ (Dietary habits and mortality in 11,000 vegetarians and health conscious people: results of a 17 year follow up)
The Vegan Society to avoid common nutrient deficiencies if your a vegan)
The Health Delusion
The Western A.Price Foundation (Vegetarianism and Nutrient Deficiencies)
British Journal of Nutrition (the influence of creatine supplementation on the cognitive functioning of vegans and omnivores)
Vegetarian Journal (about vitamin)
JAMA International Medicine (Demographic differences and trends of vitamin D insufficiency in the US population 1988-2004)
Journal of the Academy of Nutrition and Dietetics
The American Journal of Nutrition
lifesdka website
PubMed-Health benefits of docosahexaenoic acid
British Nutrition Foundation (Briefing Paper)
Dr. Fuhrman – Smart Nutrition website
World Health Organisation – Micronutrient deficiencies
The American Journal of Clinical Nutrition – Iron status of vegetarians
nutritionfoundation website
healthise – sources of iron
USDA – National Nutrient Database for Standard Reference Release
The Journal of Nutrition – the sulphur-containing amino acids: an overview
authoritynutrition website

The Value of Veg

The Department for Environmental, Food and Rural Affairs produced a report in 2013 suggesting that in the UK we consume an average of 4 fruit and vegetable portions each day. This has fallen from an average of 4.4 in 2005. The study also found a strong correlation with socioeconomic status and differences associated with gender. Despite this variation among different groups, the fact is that only 30% of people actually eat their 5 a day.

We are all used to the standard ‘5 a day’ advice which has been around since 1990, but recently there have been several attempts to promote the importance of ‘7 a day’. This could soon become the new NHS recommendation in the UK, fuelled by new research findings.

A 2014 study carried out at UCL found that people who ate 7 or more portions of fruit and vegetables each day had a 42% lower risk of death from any cause than those eating less than one portion. Both cancer and heart disease were highlighted as key factors in this trend. This research also suggested that vegetables have a greater impact on health than fruit. It was stated that each vegetable portion per day reduced ‘overall risk of death by 16%’, whereas the figure for each portion of fruit was 4%.

There is no internationally agreed figure on how much fruit and vegetables we should be eating. Not only do the recommendations here in the UK vary between different organisations, but the suggestions given by each government differ around the world. For example, in Australia it is recommended to eat 5 vegetable portions and 2 of fruit each day, whereas France suggests that people should aim for 10 portions per day in total.

The average consumption also varies hugely between different countries. The mean intake of fruit and vegetables is 33% higher in France than in the UK. This intake is also, shockingly, 2.2 times greater in Poland than in the UK.

The high sugar content of fruit is often discussed, and leads some people to limit their intake. However, the NHS has produced separate recommendations on the amount of ‘free sugars’ that should be consumed, therefore excluding the amount of naturally occurring sugars in our diet. These recommendations state that less than 5% of our energy intake should come from ‘free sugars’. This has nothing to do with the amount of sugar we are consuming in foods like fruit, vegetables and milk products. Currently the average intake of these ‘free sugars’ is greater than double what it should be in every age group, and around triple the guideline amount for teenagers. Therefore it is safe to say that we have greater issues with our diets than the sugar content of a slice of orange or bunch of grapes.

Simple Human Evolution Timeline

10 MYA  – the climate dried out
8 MYA  – our lineage split from that of gorillas
6 MYA  – our lineage split from that of chimpanzees
4 MYA  – time of the Australopithecines (possibly the first bipedal                                           walkers)
3.2 MYA – Lucy (the now famous example of Australopithecus afarensis)
was alive in Ethiopia
3.6 MYA – The Laetoli footprints in Tanzania were created
2.5 MYA – time of Homo habilis (the first species of the Homo genus and
also thought to have been the inventors of laughter)
2 MYA – time of Homo ergaster (described as a chronospecies)
1.8-1.5 MYA – time of Homo erectus (probably the first species in the
human timeline to leave Africa)
600,000 YA – time of Homo heidelbergensis (this species underwent rapid growth in brain size and is thought to have developed music as a bonding activity)
400,000 YA – the use of fire took off
230,000 YA – time in which Neanderthals were also living in Europe
200,000 YA – time of Homo sapiens (our own species, in which doctrinal religion and complex language were created)
170,000 YA  – time of the direct ancestor of all humans alive
10,000 YA  – the use of agriculture began
5,000 YA  – writing began to be used

skulls imgae