Sugar hit

One of the big reasons people struggle with maintaining a healthy diet is the fast pace of life. Although we know a wholesome, balanced diet is the best option overall, many people find themselves reaching for ‘quick fix’ energy solutions like caffeine and sugar when they’re juggling commitments in a busy day. A joint Australian and UK study recently examined the effects of caffeine and sugar on cognitive performance and mood. The results show that your morning muffin is doing nothing to improve your concentration or alertness, although a daily flat white may be useful.

Background to the research
Caffeine and glucose are two of the most widely consumed substances in the world, partly because of a widespread belief that they help us perform better. People may believe they can’t concentrate without coffee, they feel happier when they eat chocolate or they need a high calorie breakfast to push them through a busy morning. Increasingly, too, we are seeing the combination of these two stimulants in popular energy drinks.

Previous studies have shown that caffeine does, in fact, improve alertness and reaction times – particularly in people who are feeling tired and sluggish to begin with. Research also shows that sugar does increase energy levels, though this is short term. To date there have been few studies that look at the effects on concentration, alertness and mood of caffeine and glucose consumed together.

The study
Researchers grouped volunteers into three sets: one consuming glucose alone, one consuming glucose and caffeine, and a placebo group. The participants were tested for levels of cognitive performance, fatigue, stress and mood during an extended ‘multi-tasking framework’ activity. This ‘MTF’ was a computerised testing system that ran problem-solving activities across a 4-way split screen, including maths, memory tasks and visual games. The test was designed to cause frustration and stress, and lead to fatigue and decreased alertness – a lot like many of our average working days!

The study confirmed that drinks containing both caffeine and sugar (like many of the popular energy drinks) do improve our ability to multi-task by having a positive effect on speed and accuracy of performance. The caffeine/glucose combination drink showed significant improvement in areas like the speed of performing mental arithmetic and ‘working memory’, which is the part of our memory function required for short term recall, like remembering the details of an image you’ve just seen.

This result may come as little surprise – especially to anyone who enjoys energy drinks. But other results of the study were more surprising. Whilst glucose has been shown to increase energy in other studies, it showed no benefit to accuracy, numeracy or memory in the glucose-only drink participants here. There was also no change to ‘mood’ in any of the groups, suggesting that sugar does not make us happier or smarter, even if it does create a short term boost to energy levels.

The study did not examine results using a caffeine-only drink, so further research may even show that glucose has no positive effect on brain power whether consumed with coffee or not.

The combination of caffeine and glucose in drink form does give us a short term improvement in cognitive performance, although other negative health effects (like increased blood pressure) are important considerations. Digging deeper into the results proves that glucose alone does not improve mood or mental alertness, so grabbing a donut as a mid morning pick me up increases nothing but your daily calorie intake. It seems the idea that a ‘sugar hit’ at morning tea can help your performance at work is just a myth.

Andrew Scholey, Karen Savage et al (2014). Effects of two doses of glucose and a caffeine-glucose combination on cognitive performance and mood during multi-tasking. Human Psychopharmacology, 29, 434-445.