Anxious, disorientated, fatigued, irritable. This was how Rebekah Calder, 21, constantly felt. For as long as she can remember, Calder has been living with anxiety. Despite trying medication, supplements and natural remedies, her anxiety persisted.
This was until eight months ago, when she cut added sugar out of her diet. The result? She has felt much better, with improved cognitive functioning and less anxiety. She is so improved she no longer has to take her medication.
Calder is not alone. In the past few years, scientists have found links between the consumption of sugar and sugar additives to anxiety, depression and addictive behaviour.
The World Health Organisation recommends that an adult of normal body mass index should consume no more than 25 grams (six teaspoons) of sugar per day. But the Australian Bureau of Statistics reports, on average, Australians are consuming nearly two-and-a-half-times more than this.
Is it just the ‘bad’ foods such as ice cream, cake and lollies that we should be concerned about? According researchers from the George Institute for Global Health, 70 per cent of packaged food in Australian supermarkets contain added sugars.
During the study, published in 2017, 34,000 packaged foods were analysed from two categories: core foods and discretionary foods. Core foods form the basis of a healthy diet and include grains or yoghurt. Discretionary foods are energy-dense but nutrient-poor foods such as cakes or ice cream. Of the 16,000 core foods studied, over half contained added sugar. This suggests that many foods labelled as ‘healthy’ or ‘natural’ are actually filled with added sugars.
The Yoplait ‘real fruit’ strawberry yoghurt in your kids’ lunchbox today – one serve (175g) contains 21.9g or 5.3 teaspoons of sugar. That is over 85 per cent of the recommended daily intake of sugar for adults. The 220g tin of SPC baked beans you had for breakfast – 13.2g or 3.2 teaspoons of sugar, which is over half of your recommended daily intake. The 15g serve (two teaspoons) of honey on your toast – 12.4g or nearly 2.9 teaspoons of sugar. It is easy to see how Australians are consuming more sugar than is recommended. We need to look at the side effects of a high-sugar diet.
With one in five Australians experiencing common mental disorders such as depression and anxiety, and Australians consuming over two times more sugar than recommended, is there a link between them? Several factors contribute to the link between high sugar intake and poor mental health.
University College London research associate Anika Knüppel found in her 2017 study that high sugar diets increase inflammation of the brain. “There is ongoing research that low grade inflammation could increase the risk of mood disorders,” she says.
Another factor is the function of a vital growth hormone in the brain called the brain-derived neurotrophic factor. Knüppel, who is now at the Univeristy of Oxford, says BDNF has been linked with the development of depression. “This is a growth factor that has been suggested to be involved in the development of depression and lower levels have been reported in depressed individuals.”
Another contributing factor is dopamine, a neurotransmitter responsible for transmitting signals between the nerve cells of the brain. According to Knüppel, dopamine is believed to influence our mood facilitating reward and play a role in depression. Knüppel studied repeated sugar intake in rodents and found an association between changes in dopamine signalling and an increased sugar intake. She says dopamine signalling may affect humans, and these changes may play a role in depression.
The research also found that although a high-sugar diet does not necessarily cause anxiety, it can worsen the symptoms and weaken the ability to cope with stress. For example, people who have panic attacks are hyper-alert to signs of potential danger. Sugar can cause fatigue and difficulty with thinking which, to someone with anxiety, are signs of a panic attack.
However, our brains do need sugar to function. According to Virginie Lam from the Curtin Health Innovation Research Institute, approximately 20 per cent of our daily sugar intake is used for the brain. “The brain needs a constant supply of glucose, but if you’ve got too much glucose, or refined sugars, that’s been shown to adversely affect neuronal health.” She says this can result in behavioural changes and psychotic episodes.
Despite this, it isn’t all sugars we should be cutting out of our diets. Nutritionist Gemma Craven says the consumption natural sugars should be included in a healthy, balanced diet. “It’s thought that this really comes down to us having less of the core nutrients that we need such as fibre and antioxidants … when our diet consists of a lot of products with added sugars.
“We do need more research to be done to better understand the link between added sugars and mental health, but what we can say for now is that a diet rich in fruit, vegetables and wholegrains is linked with better overall health, including our mental health.”
While there is still a stigma around mental illness, Knüppel emphasises the importance of seeking professional help to reduce the burden on an individual. “Unfortunately, my research can lead to the idea that if you just did the right thing, for example eat healthily or cut out sugar, you would be fine like everybody else,” she says. “That is so not true … mental health is affected by many, many things.”
Knüppel says the next step is to conduct trial research to further establish the association. “Trial evidence would allow for a more definitive answer … The field of diet and mental health is difficult to study as both are hard to measure and are affected by many other factors … [but] I definitely see that this topic is of very high public interest and there is a lot of interesting research happening around it.”
In the meantime, early research shows signs of improved mental health with lower sugar intake, and Calder says she wouldn’t go back to eating refined sugar.
“I was on anti-depressants to purely help with my anxiety and shakiness,” she says. “But I don’t even need to take them since cutting sugar out of my diet. My doctor even said that decreasing my sugar intake assisted with decreasing my anxiety.”
While some question remain about whether sugar affects our mental health, what is certain is that a decreased sugar intake is associated with health benefits. Cutting down on sugar is a good idea, regardless.