We’ve had it drilled into us for a long time that sugar is bad for us. We know that too many sweets make trips to the dentist unbearable, that Starbucks’ sugary drinks aren’t as diet-friendly as you’d expect, and that too much Mountain Dew can give us unexpected outbreaks of acne. But what you might not have heard so much about are the effects the much-loved carbohydrate can have on the brain.
Those of you with a particularly sweet tooth may already have an inkling that sugar can be addictive. You might have noticed that you can never really eat just the one Jaffa Cake, or chocolate biscuit.
The good news is that it might not be our lack of willpower that’s causing us to chain-eat the sugary treats. A recent human study looked at how our brains respond to sugar by monitoring activity in different areas of the brain. The scientists found that when participants ate sugary foods, activity increased in areas of the brain which have been previously associated with other addictions, such as alcohol or drug addictions. Separate studies subjected rats to a program designed to cause sugar-dependence. When they took the sugar away, the rats exhibited signs of withdrawal.
We also know that a sugar overload causes a spike in levels of dopamine, a neurotransmitter which is often called the brain’s “reward chemical”, which makes us feel good and leaves us craving more.
From an evolutionary standpoint, sugar being addictive is a good thing: it means we’ll be more driven to consume it, and so we’re less likely to die of starvation. But from a modern standpoint, in a world where sugar is everywhere and we’re actually eating too much of it? Not so good.
You feel sad, you hit the Ben and Jerry’s. You feel a little bit better, or at least comforted, and you wouldn’t be blamed for thinking that sugar can act as a mood-booster. According to research however, high levels of processed and sugary foods can actually have a negative impact on our mental health, worsening symptoms of anxiety, and increasing depression risk by up to 58%.
There are several possible reasons for this. Firstly, eating lots of sugar causes a lot of peaks and troughs in blood glucose levels, whilst the brain relies on even glucose distribution. The peaks and troughs cause sugar highs and sugar crashes, which can make you feel even lower than you felt before hitting the ice cream. The sugar rushes can mimic the symptoms of anxiety, as they can cause fatigue, shaking and nervousness (to name but a few), which may make the anxiety worse.
Additionally, refined sugars can use up the body’s supply of mood-enhancing B-vitamins, which may contribute to depression risk. Sugars also interfere with neurotransmitters in the brain which are usually involved in regulating moods.
Whilst regulating blood sugar isn’t likely to be a “cure” for depression or anxiety, poorly regulated blood sugar certainly doesn’t seem to help. This doesn’t mean a cup of tea and a chocolate biscuit can’t be a nice way to relax and de-stress at the end of a long day, but it might be a good idea to avoid eating the whole pack of custard creams.
Recently, high levels of added sugar have also been linked to reduced production of brain-derived neurotrophic factor, a neurotransmitter involved with learning and forming new memories. Connections have even been made between high sugar consumption and dementia, suggesting that high levels of sugary foods can increase disease risk. Diabetes, a side-effect of high sugar consumption, in particular, has been linked to memory loss, as well-controlled diabetes has been found to prevent memory problems developing in the long-term.
One study tested this by putting mice on a high-sugar diet, and subjecting them to a series of mental and physical tests. They found that after four weeks on the high-sugar diet, the mice performed poorly on long and short-term memory tests, and on cognitive flexibility tests, in which the mice had to find new escape routes from their cages.
Some scientists have even taken to calling Alzheimer’s disease “type 3 diabetes”, because of the correlation between high blood sugar levels and insulin resistance associated with diabetes, and cognitive decline.
So the huge push in recent years to cut down on sugar isn’t just for the sake of our bodies. It’s for our brains too. And while I certainly won’t be converting to any form of sugar-free diet (is there any such thing?), I will be watching the number of those addictive Jaffa Cakes I eat in a day.
For a more detailed look at your brain on sugar, take a look at the video below: