Sugar-coated: are sweet treats affecting your mental health?

The relationship between food and feelings can be a tricky one. Even though we may have a good understanding of how too much sugar can impact physical wellbeing, the sweet impact of sugar on our mental health is perhaps a topic less known. 

Nutritional researchers can often tease out trends from studies of how what we eat may impact mood – such as people who eat a healthier diet may be happier. But it isn’t always clear whether a healthy diet promotes happiness, or happier people are more likely to choose a healthy diet.  

That said, we know that in Britain, adults consume approximately double the recommended level of added sugar, with sweet foods and drinks contributing three-quarters of daily intake [1]. Meanwhile, depression is predicted to become the leading cause of disability in high-income countries by 2030 [2].  

So, is there a link between our sweets treats and how we feel? 

Where does the sugar in our diets come from? 

Sugars occur naturally in some foods, such as fruit and dairy products. Free sugars are added to our foods and take many different forms, including white, raw, or brown sugar, honey, or corn syrup. Both types of these sugars (natural and free sugars) will make up the total sugars in food ingredients lists.  

Natural sugars provide essential nutrients that keep the body healthy. The American Journal of Public Health published findings from a survey of over 12,000 adults that found frequent fruit and vegetable consumption can increase happiness, life satisfaction, and wellbeing in just two years [3].  

How does sugar affect health? 

Glucose is the main source of fuel for our cells [4]. When we have more energy going in than we’re using, the excess is stored in the body – mainly in the liver and muscles. This feeds into what we’re all told quite often - a sedentary lifestyle, combined with a high caloric diet, plays a significant role in obesity.  

As a diet that’s high in excess sugar can lead to weight gain, one theory is that obesity could be a mediating factor between a sugar-dense diet and depression, not only via inflammatory but also through psychosocial factors like weight discrimination. 

What does sugar do to the brain? 

Our brains are extremely rich in nerve cells and neurons. It’s our most energy-demanding organ and uses one-half of all the sugar energy in the body. That means how well our bodies handle glucose, and how much glucose we’re consuming, can impact how well our brain is operating.

Diabetes and having too much or too little glucose in the blood aren’t always caused by sweet treats alone. Other risk factors for how well your body can control glucose (or insulin) include age, ethnicity, family history, or other lifestyle factors such as smoking or obesity.  

Here are some examples of how long-term low or high glucose levels in the blood can affect our brains and bodies.  

Low and high glucose levels  

A common complication of diabetes (hypoglycaemia), which is caused by low glucose levels in the blood, can lead to:  

• Loss of energy for brain function  
• Poor attention  
• Impaired cognitive function 

Having too much sugar in the blood for long periods can also have serious health problems if not treated. Hyperglycaemia, where there’s too much glucose in the blood, can increase the risk of: 

• Heart disease and stroke 
• Kidney disease 
• Vision problems 
• Nerve problems 

Type 1 vs type 2 diabetes

Type 1 diabetes is an autoimmune disorder whereby the pancreas fails to produce insulin, whereas type 2 diabetes is a metabolic disease often triggered by over-consumption of sugar, obesity, genes and a sedentary lifestyle.

Type 2 diabetes is independently associated with quality of diet and genetic factors (so a family history makes you more likely to have it) [5]. The distribution of body fat is also more strongly associated with the development of diabetes than simply being obese. People who store fat around their middle are more likely to develop it (i.e. more visceral obesity) [6]. In the early stages, type 2 diabetes may be able to be reversed or managed through lifestyle changes, by cutting down on sugar and losing weight. 

Read our ten steps to reduce your risk of type 2 diabetes or check your risk of diabetes with a simple home blood test – Advanced Diabetes Blood Test.  

Sugar and your mood 

1. Does sugar cause anxiety and depression? 

Sugar has been linked to depression, mood swings, and symptoms of anxiety.

The initial energy boost that’s gained from eating sugar can keep people craving sugary foods and drinks throughout the day (notice how it’s sometimes easier to avoid biscuits altogether, rather than just having one?). However, once the energy boost has peaked, blood sugar levels drop quickly, which may contribute to lethargy, low mood, and further cravings. 

A 2016 study strengthens the hypothesis that dietary glycemic index (GI – a rating system for foods containing carbohydrates) may play a role in the pathogenesis or progression of mental illnesses, such as generalized anxiety disorder. It concludes that dietary modification as a therapeutic intervention in the treatment of mental illness warrants further study [7]. 

Further data suggest that greater glycemic variability may be associated with lower quality of life and negative moods. Implications include replication of the study in a larger sample for the assessment of blood glucose fluctuations as they impact mood and quality of life [8]. 

If continued, these peaks and lows in blood sugar levels can trigger the release of adrenaline and cortisol (the stress hormone), causing anxiety and sometimes even panic attacks. Carbohydrate (sugar molecules) consumption has been associated with increased circulating inflammatory markers, which may depress mood [9].  

2. Does sugar help deal with stress? 

Being stressed may make you more likely to reach for something sweet over a salad. That’s because sweet foods can ‘blunt’ the effects of stress, at least in the short term by altering chemical signalling in the brain [10].  

The bad news? These effects are only temporary, and they can lead to addictive eating behaviours that affect your long-term health. Sugar-laden foods raise the risk of diabetes, obesity, and other related diseases.  

3. Could quitting sugar help anxiety? 

While addiction, stress, fear, anxiety, and depression all involve overlapping neural mechanisms, quitting or limiting free sugar may not be as simple as you think. 

Withdrawing from sugar suddenly can cause side effects, such as: 

• Anxiety 
• Irritability 
• Confusion 
• Fatigue 

Dr Uma Naidoo, who’s considered the mood-food expert at Harvard Medical School, says that people consuming high amounts of sugar in their diets can experience the physiological sensation of withdrawal if they suddenly stop consuming sugar.  

So, going cold turkey from sugar may not be the best solution for someone who also has anxiety. While it’s still a good idea to cut down on sugar, it’s best to do it gradually.    

4. Doesn’t sugar give you brainpower? 

While sugar may be the brain’s main power source, excess sugar has been shown to impair cognitive functioning, even in the absence of extreme weight gain or excessive energy intake. 

A study on the impact of adolescent sucrose on cognitive control and recognition memory found that consuming high levels of sugar-sweetened beverages impaired functions like decision making and memory [11].  

Have a look at our blog on 5 foods to boost brainpower.

How to reduce free sugar intake 

The sugar that occurs naturally in fruit, vegetables and milk has lots of benefits, so we should aim to include these within our diets. Free sugars, also known as added sugars, are a slightly different story though.  

The government recommends that free sugars (found in sweets, cakes, biscuits, chocolate, and some fizzy drinks and juice drinks) make up no more than 5% of our daily calories – that’s around 30g. Right now, the average UK adult is eating twice as much [12].  

To consume less free sugar, choose sugar-free versions of soft drinks and stick to no more than one glass if you drink juice. Don't add sugar to your tea or coffee, and avoid sugary snacks or stick to small portions.  

Check ingredients lists to see whether it contains free sugar. Keep your eye out for the names in the list below.  

Ingredients lists – other words for sugar 

Brown sugar	Cane sugar	Corn syrup
Crystalline sucrose	Dextrose	Fruit juice concentrate/purées
Fructose, glucose, or sucrose	Honey	High-fructose corn syrup
Nectars (such as blossom)	Maple and agave syrups	Maltose
Molasses	Treacle

 

The Mediterranean diet, which is usually high in vegetables, fruits, legumes, nuts, grains, fish, and unsaturated fats, has been found to directly reduce the risk of developing depression [13]. It's also linked to good heart health and low cholesterol [14]. 

How to test blood sugar levels

Checking your blood sugar levels at home can help you to reduce your risk of having serious complications both now and in the future. Sugar that is not stored or used for energy is left in the blood, where it attaches itself to haemoglobin – the part of the red blood cell that carries oxygen. 

With a blood test, you can measure blood glucose as well as HbA1c, a measure of the amount of sugar in the bloodstream over the previous eight weeks or so.   

If you have or are at risk of diabetes, knowing your blood sugar levels can help you to either prevent or manage the condition.  

Diabetes UK has lots of useful information on preventing type 2 diabetes and living with diabetes, including eating with diabetes and practical advice. If you’re concerned about your blood sugar levels, speak to a medical professional about your lifestyle to reduce your risk of or manage your condition.  

Is sugar bad for mental health? 

Diet is very important to make sure that you get all the nutrients your body needs to function at its best. If your diet is too high in sugar or processed food, you may be at risk of obesity or type 2 diabetes – which can also affect your mental health. 

The roller coaster of high blood sugar, followed by a sugar crash, may impact mood disorders such as depression or anxiety and can affect your memory and how well you sleep (see our blog on ways to improve your sleep). 

If you’re planning on majorly changing your diet, it’s best to seek professional help beforehand or get a blood test to see what’s happening inside your body. That way, you’ll be able to make informed and safe changes to positively impact your overall health.  

An Advanced Well Man or Advanced Well Woman Blood Test can give you a good overview of your health, including your risk of heart disease and diabetes.  
 

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References 

1. UCL News. 2022. High sugar intake linked with poorer long-term mental health. [online] Available at: <https://www.ucl.ac.uk/news/2017/jul/high-sugar-intake-linked-poorer-long-term-mental-health> [Accessed 26 April 2022]. 
2. Knüppel, A., Shipley, M.J., Llewellyn, C.H. and Brunner, E.J. (2017). Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Scientific Reports, [online] 7(1). Available at: https://www.nature.com/articles/s41598-017-05649-7. 
3. Mujcic, R. and J.Oswald, A. (2016). Evolution of Well-Being and Happiness After Increases in Consumption of Fruit and Vegetables. American Journal of Public Health, 106(8), pp.1504–1510.  
4. kidshealth.org. (n.d.). Definition: Glycogen (for Teens) - Nemours KidsHealth. [online] Available at: https://kidshealth.org/en/teens/glycogen.html#:~:text=Glucose%20is%20the%20main%20source.  
5. PLOS MEDICINE. 2022. Polygenic scores, diet quality, and type 2 diabetes risk: An observational study among 35,759 adults from 3 US cohorts. [ONLINE] Available at: https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003972. [Accessed 5 May 2022].
6. Lacobini, C., Pugliese, G., Blasetti Fantauzzi, C., Federici, M. and Menini, S., 2019. Metabolically healthy versus metabolically unhealthy obesity. [online] Science Direct. Available at: <https://www.sciencedirect.com/science/article/abs/pii/S0026049518302488> [Accessed 5 May 2022]. 
7. Aucoin, M. and Bhardwaj, S. (2016). Generalized Anxiety Disorder and Hypoglycemia Symptoms Improved with Diet Modification. Case Reports in Psychiatry, [online] 2016, pp.1–4. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4963565/. 
8. Penckofer, S., Quinn, L., Byrn, M., Ferrans, C., Miller, M. and Strange, P., 2012. Does Glycemic Variability Impact Mood and Quality of Life?. Diabetes Technology &amp; Therapeutics, 14(4), pp.303-310.
9. ‌Edwards, S. (2016). Sugar and the Brain. [online] hms.harvard.edu. Available at: https://hms.harvard.edu/news-events/publications-archive/brain/sugar-brain. 
10. Ulrich-Lai Y. M. (2016). Self-medication with sucrose. Current opinion in behavioral sciences, 9, 78–83. https://doi.org/10.1016/j.cobeha.2016.02.015.
11. Reichelt, A.C., Killcross, S., Hambly, L.D., Morris, M.J. and Westbrook, R.F. (2015). Impact of adolescent sucrose access on cognitive control, recognition memory, and parvalbumin immunoreactivity. Learning & Memory, 22(4), pp.215–224. 
12. British Heart Foundation (2018). Free sugars. [online] Bhf.org.uk. Available at: https://www.bhf.org.uk/informationsupport/heart-matters-magazine/nutrition/sugar-salt-and-fat/free-sugars. 
13. Parletta, N., Zarnowiecki, D., Cho, J., Wilson, A., Bogomolova, S., Villani, A., Itsiopoulos, C., Niyonsenga, T., Blunden, S., Meyer, B., Segal, L., Baune, B.T. and O’Dea, K. (2017). A Mediterranean-style dietary intervention supplemented with fish oil improves diet quality and mental health in people with depression: A randomized controlled trial (HELFIMED). Nutritional Neuroscience, [online] 22(7), pp.474–487. doi:10.1080/1028415x.2017.1411320.
14. Lassale, C., Batty, G.D., Baghdadli, A., Jacka, F., Sánchez-Villegas, A., Kivimäki, M. and Akbaraly, T. (2019). Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. Molecular psychiatry, [online] 24(7), pp.965–986. doi:10.1038/s41380-018-0237-8.