What happens to your brain when you give up sugar (2024)

It might surprise you to learn thatsugar consumption(in the UK and other developed countries at least) has actually beensteadily decreasingover the past decade.

This could be happening for any number of reasons, such as a shift in tastes and lifestyles, with thepopularity of low-carbohydrate diets, like keto, increasing in the past decade. A greater understanding of the dangers of eating excess sugar on our health may also be driving this drop.

Reducing sugar intake has clear health benefits, including reduced calorie intake, which canhelp with weight loss, andimproved dental health. But people sometimes reportexperiencing negative side effectswhen they try to eat less sugar. Headaches, fatigue or mood changes, which areusually temporary, are among the symptoms. The reason for these side effects is currently poorly understood. But it's likely these symptoms relate to how the brain reacts when exposed to sugary foods – and the biology of "reward".

Carbohydrates come in several forms – including assugars, which cannaturally occur in many foods, such as fructose in fruits and lactose in milk. Table sugar – known assucrose– is found in sugar cane, sugar beet and maple syrup while glucose and fructose are the main constituents of honey.

As mass production of food has become the norm, sucrose and other sugars are now added to foods tomake them more palatable. Beyond the improved taste and "mouthfeel" of foods with high sugar content, sugar has profound biological effects in the brain. These effects are so significant it's even led to a debate as to whether you can be"addicted" to sugar– though this is still being studied.

Table sugar, or sucrose, is a disaccharide made up of a molecule of glucose and a molecule of fructose joined together (Credit: Alamy)

Sucrose activatessweet taste receptors in the mouthwhich ultimately leads to the release of a chemical called dopamine in the brain.Dopamine is a neurotransmitter, meaning it's a chemical that passes messages between nerves in the brain. When we're exposed to a rewarding stimulus, the brain responds by releasing dopamine – which is why it's often called the "reward" chemical.

The rewarding effects of dopamine are largely seen in thepart of the braininvolved in pleasure and reward. Reward governs our behaviour – meaning we're driven to repeat the behaviours which cause dopamine to be released. Dopamine can drive us toseek food, such as junk food.

Experiments in both animals and people have shown how profoundly sugar activates these reward pathways. Intense sweetnesssurpasses even cocainein terms of the internal reward it triggers. Sugar is able to activate these reward pathways in the brain whether it's tasted in the mouth or injected into the bloodstream, as shown in studies on mice. This means its effects areindependent of the sweet taste.

In rats, there's strong evidence to suggest that sucrose consumption can actuallychange the structures in the brain that dopamine activatesas well as altering emotional processing and modifying behaviour inboth animals and humans.

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It's obvious that sugar can have a powerful effect on us. So that's why it's not surprising to seenegative effectswhen we eat less sugar or remove it from our diet completely. It's during this early "sugar withdrawal" stage that both mental and physical symptoms have been reported – including depression, anxiety, brain fog and cravings, alongside headaches, fatigue and dizziness. This means giving up sugar can feel unpleasant, both mentally and physically, which may make it difficult for some to stick with the diet change.

Although sugar is used in many of the foods we eat, consumption of sugar has been declining in the US and Europe (Credit: Alamy)

The basis for these symptoms has not been extensively studied, but it's likely they're also linked to the reward pathways in the brain. Although the idea of "sugar addiction" is controversial, evidence in rats has shown that like other addictive substances, sugar isable to induce bingeing, craving and withdrawal anxiety. Other research in animals has demonstrated that the effects of sugar addiction, withdrawal and relapse aresimilar to those of drugs. But most of the research that exists in this area is on animals, so it's currently difficult to say whether it's the same for humans.

The reward pathways in the human brain have remained unchanged by evolution – and it's likelymany other organismshave similar reward pathways in their brains. This means that thebiological impacts of sugar withdrawalseen in animals are likely to occur to some degree in humans too because our brains have similar reward pathways.

A change in the brain's chemical balance is almost certainly behind the symptoms reported in humans who remove or reduce dietary sugar. As well as being involved in reward, dopamine also regulates hormonal control,nausea and vomiting,andanxiety. As sugar is removed from the diet, the rapid reduction in dopamine's effects in the brain would likely interfere in the normal function of many different brain pathways, explaining why people report these symptoms.

Although research on sugar withdrawal in humans is limited, one study has provided evidence ofwithdrawal symptoms and increased sugar cravingsafter sugar was removed from the diets of overweight and obese adolescents.

As with any dietary change, sticking to it is key. If you want to reduce sugar from your diet long term, being able to get through the first few difficult weeks is crucial. It's important to also acknowledge however, that sugar isn't "bad" per se – but that it should be eaten in moderation alongside a healthy diet and exercise.

This articleoriginally appearedon The Conversation, and is republished under a Creative Commons licence.

* James Brown is an associate professor in biology and biomedical science at Aston University, Birmingham, UK

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