Dopamine and diets: Experts flag ultra-processed foods’ possible impacts on brain’s reward systems

13 Oct 2023 --- A team of researchers proposes classifying ultra-processed foods (UPFs), rich in carbohydrates and fats, as addictive substances. This comes following findings showing that an estimated 14% of adults and 12% of children could be addicted to UPFs, a rate similar to addiction rates for other legal substances for adults, such as tobacco and alcohol.

Researchers from the US, Spain and Brazil analyzed 281 studies from 36 countries and stress that the classification could enhance global health. However, they note that this level of childhood addiction is unprecedented.

“It has become more and more clear over the last few decades how the UPF substances created by the industry are a disaster for our physical and mental health,” Ashley Gearhardt, University of Michigan psychology professor focusing on obesity and food addiction and of of the researchers behind the analysis, tells Nutrition Insight. 

“The food industry is on record as designing these products to maximize their craveability and to hit consumers' bliss point. It is time for there to be more industry culpability, in their creation and marketing of these UPFs without adequately warning consumers' of the risks.”

As defined in the study, addiction to UPF has been compared to addiction patterns observed in substances, including neural dysfunction, impulsivity, emotion dysregulation, decreased physical and mental health and lower quality of life.

Some contend that the physiological signs strengthen the belief in the addictive potential of food. However, determining which foods can be classified as addictive remains ambiguous.

Measuring addiction 
Diagnostic frameworks such as the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) do not acknowledge the possibility of addiction to certain types of food as of yet. However, a growing body of research conducted over the last few decades suggests the opposite. 

Many studies in this area employ the Yale Food Addiction Scale (YFAS), designed to evaluate food addiction by applying DSM-5 criteria for substance use disorder within the context of dietary consumption.

The YFAS incorporates 11 criteria for diagnosing substance use disorders, including factors like reduced control over consumption, cravings, withdrawal symptoms, and persistent use despite adverse effects. Addiction is defined as “the presence of two or more symptoms in the past year and clinically significant impairment or distress.”

“These highly rewarding UPF substances trigger all the hallmarks of addiction, including reducing consumer's ability to control their intake or cut down on these products even if they are experiencing life-threatening health conditions,” says Gearhardt.Refined carbohydrates and fats may trigger levels of extracellular dopamine akin to addictive substances like nicotine and alcohol.

Addictive food choices 
The specific food items that YFAS outlined as being closely linked to behavioral signs of addiction are foods high in refined carbohydrates or added fats, such as sweets and salty snacks, which have been shown to lead to overconsumption, lack of control, intense cravings and persistent use despite adverse outcomes.

In particular, refined carbohydrates and fats are said to trigger comparable levels of extracellular dopamine in the brain’s striatum, akin to addictive substances like nicotine and alcohol.

Considering these behavioral and biological similarities, foods containing high levels of refined carbohydrates or added fats could be defined as addictive substances, according to the current paper.

“I would suggest that people focus on the quality of the food they are eating. Your diet should be composed mostly of real food - like fruits, vegetables, lean meats, and nuts. If a food product comes in a bag or a box with a list of unpronounceable ingredients, treat it with caution (even if it has health claims on it). Be aware of your triggers for consuming highly rewarding UPFs,” Gearhardt states. 

The analysis, published in The BMJ, further points out that what makes industrially produced foods, or UPFs, so uniquely addictive is that they tend to contain ingredients not found in the average home kitchen. 

While natural or minimally processed foods commonly consist of either carbohydrates or fat, it is uncommon for them to contain both simultaneously, as is overwhelmingly the case with ultra-processed food. 

The Scientific Advisory Committee on Nutrition (SACN) recently released a position statement on UPFs, which aligns with the definition of such food presented in the paper, as well as given by the YFAS. 

Effects on the body 
The blend of refined carbohydrates and fats often present in this type of food appears to have a “super-addictive” impact on brain reward systems, surpassing the effect of either macronutrient in isolation. This phenomenon might enhance the addictive potential of these foods.

“For many people, the trigger to consume these foods is for emotional reasons, to deal with stress, boredom, or loneliness. Try and develop alternative healthier emotional coping strategies (you may need to get help from a professional to do this),” adds Gearhardt.

 What is further outlined as a vital aspect of the addictive qualities of UPF is the rate at which it supplies carbohydrates and fats to the gastrointestinal tract, as substances and methods that swiftly impact the brain tend to have higher addictive potential.

UPF products undergo alterations in their food matrix, making them easier and faster to consume, enhancing their bioavailability and potentially enabling them to affect the brain more rapidly.UPF products undergo alterations in their food matrix, making them easier and faster to consume, enhancing their bioavailability.

At this year’s annual meeting of the European Society of Cardiology in Amsterdam, the Netherlands, UPFs were outlined as a cause of cardiovascular disease and strokes. 

Another study from this year, carried out in China, linked UPFs to hormonal and digestive cancer risk.

The researchers conclude that not all foods induce addictive behaviors, but among the foods accessible for consumption, UPFs appear to be the most likely candidates for addictive substances. 

They also assert that further research is required to pinpoint the exact mechanism through which these foods trigger addictive responses while reaffirming that refined carbohydrates and fats are “clearly consumed in addictive patterns” and that this consumption trend is “leading to deleterious health outcomes.”

“Focus on the intake of food to nourish your body and brain,” reminds Gearhardt.

“This is not easy in a food environment where access to healthy food can be limited, especially for individuals who are poor, and ultra-processed foods are cheap, convenient and heavily marketed. We have to advocate for policies to make it easier to eat healthfully in the modern world,” she concludes. 

By Milana Nikolova