‘Hangry’ humans – why an empty stomach can make us mean

There’s no point denying it, at one point or another, we’ve all been guilty of being ‘hangry’. Whether you’re a frequent culprit or just an occasional offender, getting angry when hungry is a common crime in many households, and one that can result in arguments, ‘fallings out’ and even a night spent sleeping on the couch. But is it really our fault or is there a more biological reason to blame? An increasing body of research suggests our blood glucose may be the real culprit.

The glucose we obtain from our diet is a key source of energy, required for our bodies to function and delivered to all of our cells via our blood. Out of all the organs of the body, our brain is the most energy-consuming, using around 20% of the energy our bodies produce. It also relies almost completely on glucose as its energy source, making an efficient supply of this sugar essential to maintaining proper brain function. This is particularly true for higher-order brain processes such as self-control, which require relatively high levels of energy to carry out, even for the brain. Since self-control allows us to resist such impulsive urges as out-of-control eating or aggressive outbursts, if our brain does not have sufficient energy to perform this process, our ability to stem these unwanted impulses can suffer.

Low levels of glucose in our blood can also result in an increase in certain chemicals in our body, believed to be linked to aggression and stress. Cortisol, for instance, colloquially named the ‘stress hormone’, has been shown to increase in individuals when they restrict their caloric (and therefore glucose) intake. Neuropeptide Y concentrations have also been shown to be higher in individuals with conditions associated with impulsive aggression when compared to healthy volunteers.

Given such evidence, it therefore makes sense that low levels of blood glucose, like those experienced when we are hungry, could plausibly lead us to become more aggressive. The association between blood glucose and level of aggression has been observed in multiple studies, including Ralph Bolton’s 1970s research of the Quolla Indians. These Peruvian highlanders are well-known for their high rates of unpremeditated murder and seemingly irrational acts of violence. Having observed both this behaviour and a strong sugar craving among the Quolla Indians, Bolton decided to investigate the possible link between hunger and aggression. In agreement with his hypothesis, Bolton found that the Quolla Indians commonly experienced low blood glucose levels, and that those with the lowest levels tended to be the most aggressive.

In another, more recent study, similar findings were observed in college students who took part in a competitive task. Participants were randomly assigned to consume either a glucose beverage or placebo drink containing a sugar substitute. Following this, participants then competed against an opponent in a reaction time task, which has been shown previously to provide a measure of aggression. Before beginning the task, the students could set the intensity of noise their partner would be blasted with if they lost. As predicted, participants who drank the glucose drink behaved less aggressively towards their partner, choosing lower noise intensities, compared with those who had consumed a sugar substitute. This suggested that hunger-related aggression, or ‘hangriness’, could be ameliorated by boosting one’s glucose levels.

One notable (though some may argue rather dark) study into the ‘hangry’ condition investigated the relationship between blood glucose and aggressiveness in married couples. As well as pitting spouses against each other in a similar reaction time task to the one described above, participants were also given a voodoo doll of their partner and told to stick pins in the doll each evening, depending on how angry they were at their partner. (Warning, do not try this at home). As with previous studies, lower levels of blood glucose resulted in participants blasting their spouses with higher noise intensities and sticking more pins in the voodoo dolls, suggesting greater levels of anger and aggression.

While these studies do not necessarily ascertain causality, the relationship between low blood glucose and the tendency to become aggressive makes biological sense, since glucose is the main energy source our brains need to control such negative impulses. As observed in studies and experienced by many of us, ‘hangry’-related crimes can also be easily avoided by supplying the potential offender with food, further supporting the role of glucose in hunger-related anger. So next time ‘hangriness’ threatens to ruin the harmony in your household, fill your mouth with food rather than foul language, and save yourself a night banished to the couch.

Post by: Megan Freeman

Save

Save

How your smartphone could improve your health

Lamiece Hassan on why unlocking the potential of smartphone data could be the next frontier for health research.

I have an addiction to my smartphone. It helps me to navigate not only the streets of my adopted home city of Manchester, but life in general; everything from banking to shopping, scheduling, videoing, networking, dating and, on occasion, making phone calls.  And it helps me to monitor things, like my patterns in exercise, diet and sleep. I’m the type who posts annoying screenshots of their step count on Instagram after a big night (#danceallnight). To some this could seem a somewhat unhealthy, yet common, obsession. However, I’m keen to learn how our increasing attachment to technology can actually help to generate new insights into health and disease and benefit others.

You see, your smartphone is a sort of digital Swiss Army knife, jam-packed with vital sensors and tools that collect, process and transmit all manner of data. Furthermore, it’s a constant companion, always on and always with you, effortlessly tracking your everyday routines. To researchers like me, who would otherwise have to dedicate significant time and effort to collecting these data themselves, smartphone apps are appealing, inexpensive tools for generating a wealth of high quality data on everyday life on a mass-scale.  Moreover, this type of ‘big data’ could hold the key to better understanding and treatments for many health conditions – like seasonal allergies, dementia and Parkinson’s.

One area where patient data is currently lacking is seasonal allergies.  Allergies are basically the result of the body’s immune system ‘misfiring’ and incorrectly responding to harmless substances or ‘allergens’, such as pollen. These allergies are very common in the Western world. One in four people will experience an allergy at some point in their lives and this number is increasing.  However, the causes are unclear.  Dr Sheena Cruickshank, an immunologist at The University of Manchester, explains the situation: “The rise in seasonal allergies like hay fever could be down to all sorts of things – such as changes in pollen exposure, pollution or maybe a lack of childhood exposure to germs. We have good quality data on many of the suspected causes but we don’t know how people are actually being affected. Gathering real-time data on a mass-scale about when and where symptoms occur could really help to change all of that.”

A nationwide study is currently underway to fill in these blanks and try to better understand seasonal allergies, all using a smartphone app called #BritainBreathing*. Allergy sufferers act as ‘citizen sensors’, using the app to keep a daily log of their symptoms (or lack thereof) like sneezing, itchy eyes and wheezing and track them over time. The app automatically does the rest, automatically sharing anonymised reports with the research team, with a time-stamp and approximate location.

Whilst sometimes trivialised, hay fever symptoms can be severe for some people and it is often associated with other conditions, such as asthma and eczema. Caroline, now 32, has had all three since childhood: ” I’ve had eczema since I was a baby, then I got hay fever and asthma later on around primary school age. At one point I was constantly on antihistamines.” Could a smartphone app help people like Caroline get a better handle on what their triggers might be? “When you’re young everyone else manages it for you, but when you get older you need to build up a picture in your own head to start to think about triggers: what is it, where was I, what was I doing at the time? Everyone carries their phone around now so that would be a good place to start.”

Indeed, decoding data has been key to other recent breakthroughs in the world of allergy research.  Whilst big is often beautiful, advances in statistical methods have arguably been just as important to unlock the insights hidden within the data. For example, combining data from several long-term studies (which collectively tracked almost 10,000 children from birth) helped researchers to question the stereotype of the so-called “allergic march”; a supposedly classic progression of symptoms starting in childhood, beginning with eczema, then progressing to wheeze and finally hay fever.  Using sophisticated analysis techniques, researchers showed that individuals fall into one of several ‘profiles’ and that this classic sequence is much less common than once thought (less than 7% followed this pattern). Findings like these appear to strengthen the case for acknowledging how variable patterns of allergic conditions can be, with slightly different symptoms and trajectories.

Teaming smartphone data with data from research studies like these has, to date, been an area with largely untapped potential. However, researchers are increasingly recognising the opportunities in bringing together different sources of data – including smartphones, wearable fitness gadgets and medical records – to shed light on diseases like dementia and Parkinson’s. For example, the 100 for Parkinson’s project invited people to use a smartphone app to track aspects of their health (including sleep quality, mood, exercise, diet and stress) for 100 days and donate their data to research.

Of course, it’s not all plain sailing. Some have expressed concerns about the quality of data, the ability to produce meaningful analyses and safeguarding personal information. However, the ability to work with the public to build large datasets to allow us to gain insights into both health and disease states mean that it’s an option increasingly being considered by a large array of scientific and medical fields. Is the smartphone the future of health research or is the challenge of disentangling the complex data generated by constant tracking more trouble than it’s worth?  We’ll just have to wait and see. I, for one, think it’s an opportunity too big to pass up.

*The free Britain Breathing app is available on the App Store and Google Play now.

Post by: Lamiece Hassan

Save

Seasons and Sefton

In temperate regions such as the UK, our ecosystems experience seasonal dynamic fluctuations, as our moderate climate slowly fluctuates throughout the year. These fluctuations follow an annual trend, with many species of tree blossoming in spring before shedding their leaves in an impressive colourful autumn display leaving just bare branches through the winter days. In sync with this, animals appear to breed as temperatures increase yet hibernate through cooler days.

For those of you living in Liverpool, student or otherwise, it is well known that Sefton park is one of the most popular places to visit for its aesthetic beauty. I have lived in Liverpool for 4 years and have always been intrigued by the ecosystems it has to offer. Here I have documented how the park changes throughout the year by capturing photos at four different occasions between September 2016 and May 2017:

September 2016
November 2016
March 2017
May 2017

The science behind these changes is fascinating. One of the most noticeable differences observed in the park can be seen in the trees, specifically in how their leaves reflect the fluctuating seasons. Throughout the winter months, trees enter a period of dormancy in order to survive the low temperatures. However, despite their stark dormant appearance, deep within their branches they are actually busy maintaining themselves through respiration and enzyme synthesis and preparing for the coming spring.

As spring approaches, these trees begin to bud leaves and flowers, a change brought about in response to an increase in temperature and light availability. Throughout the summer months, different shades of green dominate the park. It is the photosynthetic pigment chlorophyll which gives leaves their vibrant green colour. This pigment enables plants to absorb energy from sunlight, specifically, it absorbs light in the blue and red portions of the electromagnetic spectrum while reflecting the near-green portion, therefore producing the vivid shades of green we see throughout the summer.

The breakdown of chlorophyll in the autumn reveals carotenoids in the leaves causing them to change from green to yellow/orange and creating a variety of colour throughout the park. Eventually, leaf abscission occurs.
Leaf abscission refers to the controlled process by which trees shed their leaves. This occurs from the Abscission zone (at the base of the leaf’s stem). Abscission zone cells differentiate in early plant growth and are able to respond to a number of environmental stressors and plant hormones. When light levels start to reduce and chlorophyll is degraded, levels of the plant hormone auxin decrease which in turn increases sensitivity in the abscission zone to another hormone ethylene. When the plant is exposed to ethylene cell wall-degrading enzymes such as cellulase and polygalacturonase are activated and abscission occurs.The trees then enter dormancy and the process repeats itself. There is a clear seasonal regulation of growth. And, it’s not only trees which follow this cycle, other flowering plants also respond to changes in seasons and sunlight which, in turn, allows many insects and mammals to thrive building a complex and beautiful ecosystem around these plants.

The images included in this article provide a visual representation of how our planet constantly changes. Sefton provides city dwellers with the ability to witness these changes first hand throughout the year – and we can guarantee you a mystical view on whatever day you decide to visit.

Take home message: Next time you take a trip to Sefton, have a look at the forever changing ecosystems and think about the biological processes occurring beneath the visual changes.

Post by: Alice Brown:

References
http://www.journals.uchicago.edu/doi/abs/10.1086/283724?journalCode=an
https://link.springer.com/chapter/10.1007%2F978-94-011-4453-7_45#page-1
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1087143/pdf/plntphys00512-0027.pdf
http://postharvest.tfrec.wsu.edu/pages/PC2000F
http://scienceline.ucsb.edu/getkey.php?key=1110
https://www.ncbi.nlm.nih.gov/pubmed/17737985

Save