Humans are biologically wired to prefer sweet tastes, which is a problem when we live in a world of Uber Eats, says Dr Nicole Avena.
I grew up as a kid in the 1980s with fizzy drinks and sweets in our house as a regular thing. I wasn’t aware how poor my diet was until I left home for college. What really got me interested in sugar was when I started graduate school and began looking into the science behind it. During research into eating behaviours and addiction, I became fascinated by how sugar affects the brain, especially in ways that mimic addictive drugs.
I started to look at processed food products – many contained so much added sugar, and in amounts we would never see in nature. I realised our brains were being blasted multiple times each day with the effects of 10 times that amount of sugar (in nature) from cookies, cakes, and protein bars. Not to mention “healthy food” like some yogurts, salad dressings and fruit smoothies.
In the 1970s, fat was demonised because of its supposed negative impact on heart health and links to obesity. People believed fat = bad, carbs = good, and the idea was companies were doing you a favour by taking it out of the products. But they found that if you take fat out of the yogurt, it doesn’t taste good, and so companies added sugar to fix the problem.
How sugar affects the brain
I’ve spent the last 25 years studying sugar as an addictive substance. Back in 2001, no one had scientifically shown that food and drugs could be classified as equally addictive. But the more I studied it, the clearer it became that sugar isn’t just a treat – it can hijack our biology.
While my peers were going to gigs, I spent my evenings feeding rats a liquid sugar solution, and I noted something interesting. The rats with unlimited access to the sugar were in fact bingeing on it and showing other signs of addiction. They were escalating their intake each day, and when we deprived them of the sugar, they showed signs of withdrawal. They also seemed to be craving it. When we looked at what was happening in terms of their neurotransmitters, the brains looked more like a rat that was hooked on drugs.
Since those early rat experiments, many clinical studies have shown that humans who consume highly processed foods containing high amounts of sugar may also experience symptoms of withdrawal. People who have been bingeing for years need more to feel the pleasurable effects – like a drug addict, they are chasing a sugar high that is unattainable. Even though our rational brains know this, the primitive parts of our brains win out.
Sugar stimulates the brain’s reward system, particularly the release of dopamine in areas like the nucleus accumbens: the same region activated by drugs like cocaine or alcohol. To be frank, our brain doesn’t know if we are shooting heroin or eating a cupcake. This is why it makes sense that many of the foods we eat, especially highly processed man-made foods loaded with added sugar, affect the brain like a drug.
Sugar is a silent killer
Sugar has not only been shown to have destructive effects on metabolic health, but new research shows it can negatively impact learning, memory and impulse control. Diabetes, cardiovascular disease and fatty liver disease are now being tied back to our diet, with sugar as the main culprit. For example, two or more servings per day increases your risk of dying from CVD by over 30%.
In 2020, a large analysis including over 35 studies (published in the European Journal of Epidemiology) found every 250ml increase in sugar-sweetened beverage intake increases risk of mortality by 4%. That’s not even a can of soda. Another large study found sugar-sweetened beverage intake, even after taking into account BMI, dietary and lifestyle factors, increases your risk of dying.
You’re not going to drop dead from eating one cookie, but many years of a poor diet rich in added sugar will not only reduce your life span, but make it much more likely to be fraught with illness, disease and unhappiness.
We’re born addicted to sugar
We’re biologically wired to prefer sweet tastes from birth – it’s an evolutionary survival mechanism. Breast milk is naturally sweet, and sweetness signals energy and safety. If our ancestors stumbled across a berry bush, the sweet berries on the bush were safe, but if they ate the sour ones on the forest floor, they would get sick, possibly die. This innate preference becomes problematic in today’s food environment, where highly concentrated sources of sugar are everywhere. We have the brains of starving hunter-gatherers, but live in a world of Uber Eats.
Genetics play a role in how sensitive we are to rewards, including food, and some people may have variations in dopamine or opioid receptor genes that make them more prone to addiction-like responses to sugar. So while the environment is a trigger, your biology can influence your vulnerability.
Dopamine release is the hallmark of drug use: each time a person smokes a cigarette, drinks alcohol, uses heroin or eats sugar, dopamine is released in reward-related areas of the brain. When this happens, additional changes occur in the brain that make the individual crave the drug, contributing to the vicious spiral of addiction.
Cravings are a natural part of being human, but most people don’t know whether a craving is biological (i.e. we have low blood sugar or low iron, and our body is physiologically in need of food), or something else. Hedonic cravings are driven by pleasure, not hunger. You might feel full but still want dessert; that’s hedonic hunger at work. These cravings are triggered by cues, emotions or habits.
In 2015, a large review study analysing 45 research papers (published in Obesity Reviews) found seeing the food and the subsequent craving significantly influences eating behaviour.
Giving up sugar is like withdrawing from drugs
When a brain is addicted to drugs, specific neurotransmitters start to act differently in key regions, specifically the reward-related region. If you’ve been eating a diet high in added sugar and processed foods and you make an abrupt change, you might feel good for a few days, but then suddenly you may suffer from symptoms including irritability, anxiety, lethargy and headaches. This is sugar withdrawal.
Research has shown adults with high sugar intake score significantly lower on cognitive impairment tests. Furthermore, adults who consume more than 11 teaspoons of sugar per day are also more likely to score lower on immediate and delayed memory tests, as well as verbal memory. Remember, 11 teaspoons of sugar is less than the sugar in a 590ml bottle of Coke.
Recent studies have also suggested a link between excessive sugar intake and the development of dementia, with some even beginning to consider whether Alzheimer’s disease should be called ‘type-3 diabetes’. Persistent hyperglycemia, found in individuals who have type 2 diabetes and pre-diabetes, has been shown to be associated with developing dementia and cognitive impairment.
Cancer cells love sugar
Cancer cells grow and divide much faster than other cells in our body, which explains why they take in so much sugar for fuel. But this doesn’t necessarily mean sugar from our foods “feeds” the cancer cells. While there’s still plenty of research that needs to be conducted to understand the complex relationship between dietary factors and tumour growth, there is a lot out there supporting a strong association between sugar and cancer.
One reason for this relationship may be due to the pro-inflammatory nature of sugar. Inflammation can damage the DNA in our cells, which leads to poor replication and gene mutations, leading to cancer. Another is that sugar stimulates the secretion of insulin and insulin-like growth factors, which can promote tumour growth and progression. This may partially explain why one large study analysing dietary information from over 100,000 participants found those with the highest total sugar intake had the highest risk of cancer. Higher sugary beverage intake is associated with almost a 60% higher risk of obesity-related cancers, while sugar-sweetened beverages have been positively associated with death from all cancers, especially breast cancer.
Sugar is linked to ADHD and depression
We often use sugar to attempt to self-medicate mental health issues like mild to moderate depression and anxiety, but in reality, added sugar often promotes mental unwellness. Although the underlying causes of many mental health conditions are out of our control, like genetics and our biochemical make-up, there are things within our control that increase or decrease our risk.
Although the causes of ADHD are controversial and multifactorial, one of them may be related to neuro-inflammation. So, if neuro-inflammation could be contributing to ADHD, you can see why sugar may be contributing to this increase, or at least making it worse.
Sugar is the new tobacco
Some of the unhealthiest people I have met and worked with have been what would be considered a healthy weight. Yet, they were totally addicted to sugar, and bingeing on it regularly. They felt out of control. They wanted to change their behaviour but felt stuck in the sugar vortex.
Even the tobacco industry admits their products are addictive (see the warning labels and public health campaigns they sponsor), though it took 50 years and quite a few lawsuits. And I think it’s going to take time when it comes to food, but hopefully we’re getting closer. Because the longer we wait, the more people are going to end up having medical complications that could have been mitigated with better choices.
We need to enact policy changes to help people understand that a lot of these processed foods are highly addictive, so they can think twice about what they want to eat, or decide how much of it they want to eat. Some countries now add warning labels on food, which is a great idea. So red means very highly processed, versus green, which signifies minimally processed.
We live in a sugar-centric world. It is pushed on our kids, and hidden in food products using different names. Grocery store positioning is like luxury real-estate shopping, with added sugar found in things that are purposely placed at eye level in stores. Companies pay to have their products in those spots. The poorer brands (often the healthier options) are way up top or below, where you can barely reach them. Companies know the average person hitting the grocery store is a woman with kids who wants to get in and out fast.
Sugar addiction is still controversial among some scientists
When I first started presenting my research at conferences, I got pushback. Many academics and medical doctors believed addiction is for alcohol and cocaine, not cakes and crisps. But I’d argue their critique hinges on a narrow view of addiction.
While sugar doesn’t create the same physical dependence as synthetic opioids, it does meet the behavioural and neurochemical hallmarks of addiction. We’re not saying sugar is identical to heroin, but that it activates the same systems in the brain in strikingly similar ways.
In March, Frank Hu, chair of the department of nutrition and the Fredrick J. Stare professor of nutrition and epidemiology at Harvard’s T.H. Chan School of Public Health, argued in The Harvard Gazette that lumping sweets with alcohol and nicotine is a problem. My response is that the only reason sugar is not recognised as an addictive substance is because major organisations like the World Health Organisation (WHO) and American Psychiatric Association (APA) have not endorsed it as being an addictive substance. Similar to how gambling wasn’t “addictive” until medical authority groups “decided” it was.
I am an author on petitions to both the APA and WHO, calling for ultra-processed foods to be recognised as addictive substances, and these are presently being reviewed.
Sugar meets the APA’s criteria for being a substance of abuse. There are 11 criteria, including tolerance, withdrawal, hazardous use and social/interpersonal problems, and meeting just one puts you at risk. Six is said to be an addiction. Sugar checked all the boxes as an addictive substance.
Some critics say focusing on sugar oversimplifies overeating and ignores the role of other palatable foods. That’s a fair point – sugar isn’t the only issue. Highly processed foods that combine sugar, fat and salt are engineered to be hyper-palatable and override satiety signals. But sugar is often the “gateway” component that drives cravings. It’s not the whole story, but it’s a critical piece.
People say: “I grew up having those cookies and I turned out fine.” But the problem is that the foods we grew up with, even 20 years ago, are vastly different to the foods we have now. Manufacturers use additives, colourants and chemicals specially designed to ensure “food” will last on a shelf for six months without spoiling and taste really good. Although you can consume them, I don’t consider them to be actual food. Food should be a nutritious substance that maintains life and growth.
Sugar has been around for centuries and, for most of that time, we have lived in harmony with it. We need food to survive, and many foods that are good for us (fruits, some vegetables, milks) naturally contain sugars in amounts that aren’t bad for us. But people are increasingly relying on fast food and processed grocery store foods as a staple. And they all contain added sugar.
Twenty-five years ago, doctors viewed obesity as caused by a lack of willpower. I hope our work has changed that – now we understand the addictive hold sugar has on some people.
– Interview by Liz Hoggard
Top strategies to beat sugar addiction
Bin added-sugar foods
Go through your refrigerator and record how much added sugar is in each item and whether it contains an alternative sweetener. Do the same thing with your pantry. Remove high-sugar foods from your house to avoid temptation.
Eat balanced meals
Protein and healthy fats slow digestion, keep cravings at bay and keep blood sugar stable. Foods rich in fibre, such as wholegrains, legumes, fruits and vegetables, keep you fuller for longer, while high-carbohydrate foods such as sweetened drinks, pasta, pizza and high-fat foods, such as fried foods and baked goods, produce very little satiety.
Identify emotional triggers
Keep a cravings journal to spot stressors when you use food to soothe or reward - especially when you’re feeling low, or coping with withdrawal. Think about specific times (or people) that lead you down a path of sugar-seeking.
Find healthy swaps
Try fruit, dark chocolate or cinnamon tea when cravings hit.
Find non-food rewards
When you’ve done something well, buy yourself something. See a show. Play sport. It’s about retraining the reward system so we get reinforcement from things that don’t pose a significant risk.
Avoid sweeteners
I view them like methadone: it’s better for you than heroin and can help when you’re trying to detox, but you don’t want to stay on it forever.
Eat solid food
Liquid calories from sugar go down super-quick and you don’t get satiated. Solid foods require chewing, which slows consumption and increases the oral sensation of the food.
Think before you eat
Slow down and ask yourself if you’re truly hungry.
Don’t panic if you ‘relapse’
Don’t beat yourself up and view the slip-up as a total failure. Consider it a learning experience so you can better cope next time you find yourself in a similar situation.
Remove images of food porn
Go through your social media accounts and unfollow food-focused accounts that post photos of desserts and other treats.
Get enough sleep
Lack of sleep increases ghrelin, your hunger hormone. Going to bed early can be the best solution to coping with sugar withdrawal.
Stay consistent
The less sugar you eat, the less you crave it. It’s about small incremental changes, like not having sugar in coffee. You’ll see the benefits almost immediately.