A friend of mine keeps a drawer full of emergency chocolate chip cookies at work. They are for those moments, he says, when after an intensely stressful moment, everyone’s brain ‘crashes’ and his team need sugar to keep going and continue to work at peak mental performance. Suddenly feeling light-headed and energy-drained after an intensely stressful experience is one of the oldest survival mechanisms we have evolved to have.
What is actually happening?
As soon as a stress response is triggered, the brain activates sympathetic nerve activity, leading to the release of cortisol and a switch to a completely different physiological baseline. The heart rate is elevated, blood pressure is raised and blood is diverted away from the abdominal organs and into muscles. The amygdala within the brain (the emotion centre) is on high alert and vigilant for every possible threat or danger. The brain diverts all resources to defence in the face of attack. The brain is the command centre of the defence force. It is the General of the body’s army. All resources get diverted to the brain. Sugar is one such resource.
Pushing sugar towards the brain
Glucose can enter cells around the body via a particular type of gate: the GLUT-4 receptor. Only insulin has the key to this gate.
It unlocks it to let glucose through. When blood glucose levels rise, insulin is released.It unlocks the gates around the body and glucose is taken up by muscle cells and fat cells to bring levels down again. This gate is not present in the brain, so the brain does not need insulin to access glucose. During acute stress, the GLUT-4 receptor becomes temporarily insulin resistant. Glucose suddenly stops being removed from the blood and its concentration in the blood shoots up. This rise in blood glucose pushes glucose into the brain. In effect, this mechanism ensures that glucose is being diverted to the brain at a time when the brain’s performance is absolutely crucial.
So, is it a good thing?
Thousands of years ago, it probably was. Right in the middle of being mauled by a bear, when absolutely exhausted, muscles aching and profusely bleeding, it would have helped to have every last drop of energy diverted to the brain so it could think through a strategy to overpower the bear and survive. Today, our biggest source of stress is psychosocial stress. The bears we encounter today take on a more human form and we are mauled by unpleasant behaviour, emotional injury and aggressive encounters. We don’t need to run away and we don’t need to overpower our opponent with strength and stamina. We don’t use up as much energy in dealing with these stressors.
We no longer need blood to be diverted to our muscles or for our pupils to dilate. Unfortunately, the mechanisms of stress are wired into our brains so tightly that we still react to a traffic jam the same way we used to react to a bear. Although the brain is at no risk of running out of energy, we still become temporarily insulin resistant to divert glucose to the brain, the second we become stressed. Acute stress makes glucose levels within the brain go up by up to 12 times the baseline level. As soon as the moment of stress has passed, the GLUT-4 receptors suddenly respond again to insulin and there is a surge of glucose out of the blood and into peripheral tissues. This causes a sudden drop in glucose. Hence the feeling of a ‘sugar crash’.
You probably don’t need the sugar
The first step is to recognise that the sugar crash is a physiological reflex. If you are perfectly healthy and don’t suffer from a medical condition, you probably don’t need the sugar that you think you do – and neither does your brain. Instead of reaching for a sugary snack immediately after a stressful experience, you may try to wait a moment to see if the feeling subsides. If not, reaching for snacks that don’t affect insulin levels will minimise the yo-yo effect of insulin and glucose on the brain.
Please Note: this site is for discussion only and should not be used as a source of medical advice. Please consult your medical doctor before making any changes to your diet, lifestyle or medications.
Straub RH. Insulin resistance, selfish brain, and selfish immune system: an evolutionarily positively selected program used in chronic inflammatory diseases. Arthritis Research & Therapy. 2014;16(Suppl 2):S4.