Cognitive Fitness Chapter 8 – Glucose – Your brain needs sugar… really?

Our latest research looks at the factors that most impact our cognitive performance – so individuals and organisations can understand and adopt best practices to get everyone’s brain in peak condition. Last time we looked at the impact that caffeine has on the brain. This time we are looking at the effects of glucose on your brain – like caffeine it needs to be handled carefully!

Glucose is a type of sugar and is the primary source of energy for the human brain. To ensure for maximum cognitive ability, the brain needs a constant supply – normally obtained from recently eaten carbohydrates. An inadequate supply of it will result in a significant decrease in cognitive performance. The frontal cortex (described as the “CEO of the brain”) is particularly sensitive to falling glucose levels, likely resulting in some confused thinking – but high levels of glucose will damage other cells in the body so as ever, a balance is required.

Why is the impact of glucose on the brain important to understand?

Human brain studies show that dips in glucose availability can have a negative impact on attention and memory and that consuming glucose can enhance these aspects of cognitive function. The brain also uses more glucose during particularly challenging mental tasks.
So it’s important to keep blood glucose levels at an optimum level for good cognitive performance – something that’s not always easy to do, but having regular meals can help to achieve this. This links back to the advice we gave on breakfast – imagine how many hours there are between your last meal of the day and breakfast… by which time your brain can be crying out for fuel! Its vital that to maintain mental performance, you feed your brain.

Despite some pretty sophisticated regulation of its glucose fuel requirements, the brain does experience short-term dips in glucose availability. These can impair cognitive functions such as attention and memory. By contrast, the parts of the brain that look after vital functions are more hardy and less sensitive to a fall in glucose levels (for example your breathing won’t be compromised by a drop in glucose levels… you’ll more likely suffer some confusion and loss of concentration).

When a drop in attention and memory occur, taking additional glucose can improve short term memory and attention – and it has even been shown that the uptake is increased under mildly stressful conditions such as challenging mental tasks.

How much glucose / sugar is ok?

Some experts suggest that the brain works best with about 25 grams of glucose circulating in the bloodstream – about the amount found in a banana – and the body will break down other foods (fats, carbohydrates, even protein) to turn them into glucose if the level gets too low.

Whilst branded ‘high energy’ drinks may provide a ‘sugar rush’ with a feeling of immediate energy, this will be short term and most nutritionists agree that sugar provided through fruit and other natural products taken as part of regular nutrition breaks should be adequate – and/or simply eating regular meals to provide a continuous supply of fuel.

Do different foods make a difference?

Heard of the glycemic index (GI)? It ranks foods according to how they affect blood glucose levels (or blood sugar levels if you like). Against a standard of 100 (pure glucose) low GI foods are 55 or less and high GI is 70 or more. Roast potatoes are high on the index (c85), because they cause blood sugar to rise very quickly, but celery has a low glycemic index (c45) and will turn into glucose more solely, providing a steadier supply of energy to the brain and dealing effectively with hunger.

Combining low GI / high fibre carbohydrates can slow absorption even further. For example, white bread is high glycemic (72), is digested quickly and causes a stressful, brief spike in glucose levels. Adding some meat or other protein to the bread slows down the speed at which glucose is absorbed.

That said, not all fats are equal in terms of their ability to lower the GI of a meal. Despite fat’s ability to lower the GI of a meal, not all fats are equal. Trans fats, common in fast food, are the worst; saturated fats aren’t great but unsaturated fat is the healthiest.

Cognitive Fitness - Glucose - sugar - cognitive performance - awa - advanced workplace associates - workplace management

What would we advise?

    1. Make sure you eat foods that contain sugar evenly throughout the day (e.g. fruit, vegetables) – small frequent meals work well
    2. According to The World Health Organisation you should have a maximum of 25g of ‘free sugar’ (i.e. processed sugar, bread, drinks and other foods where refined sugar has been added) – equivalent to 6 teaspoons a day
    3. Bear in mind that fruit drinks sound healthy but have often had a lot of the goodness of the fruit removed, leaving the sugar behind. They can contain as much sugar as regular coke.
    4. Check the labelling on the things you eat to identify natural vs added sugars. Sugars occur naturally in foods such as fresh fruit and milk – and you don’t need to cut down on those. Look out for sucrose, glucose, fructose, maltose, hydrolysed starch and invert sugar, corn syrup and honey… all are “added sugars” (subject to the maximum above). Remember there is a lot of sugar in processed foods and drinks (through corn syrup) – so you may be consuming more added sugar then you think.
    5. If you eat a balanced diet, there is no need to add more sugar for the brain. Use “high energy” drinks sparingly. A sugar rush is just that – a temporary spike in glucose levels – and is no substitute for giving your brain and body what they need to function optimally without yo-yo-ing up and down.
    6. Know yourself! If you typically don’t eat much, over exercise or skip meals, even a minor dip in glucose is enough to make you a bit fuzzy – try to notice what happens when you skip meals or go too long without a healthy snack.

Give your brain a great day – regular meals during the day keeps a good supply of energy and glucose available for your brain – keep the high glucose energy drinks for when you really need a short term boost. Water is much better to keep you hydrated!

Next time we’ll start to look at the environmental factors that came out of the research. The seventh factor is Noise (earplugs at the ready!).

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