“Ice cream ‘could be as addictive as cocaine’,” reported the Daily Mail. In a bid to scoop its rivals, the newspaper claimed that new research had whipped up “concerns that the dessert could be genuinely addictive”.
It’s not clear who exactly had these chilling “concerns” over the possible addictive qualities of the frozen snack, but the study in question looked at measures of brain activity in 151 teenagers while they drank an ice cream milkshake. During the scans, teenagers who had frequently eaten ice cream over the past two weeks showed less activity in the “reward areas” of the brain that give pleasurable sensations. This reduced reward sensation was reported to be similar to what is seen in drug addiction as users become desensitised to drugs.
Unsurprisingly, the study did not directly compare brain responses to or cravings for ice cream with those for illegal drugs. Therefore, while some aspects of the brain’s response may be similar, it is not correct to say that this study has found that ice cream is “as addictive” as illegal drugs.
It should be noted that the study included only healthy teenagers of normal weight, and its results may not represent overweight or older people. It also only tested one food, so the results may not apply to other foods.
Where did the story come from?
The study was carried out by researchers from the Oregon Research Institute in the US. Sources of funding were not clear. The study was published in the peer-reviewed American Journal of Clinical Nutrition.
The newspapers focused on the suggestion that ice cream is “as addictive” as drugs. However, it is not possible to conclude this from the study.
What kind of research was this?
This experimental study looked at whether regularly eating ice cream reduces the brain’s pleasurable “reward” response. When we do things that support our survival, such as eating and drinking, the brain gives us a pleasurable reward sensation, reinforcing this behaviour and encouraging it in future. A similar process is also believed to occur in drug addiction, where a person’s reward response to the drug decreases with repeated exposure, leading to a need to take more of the drug.
The researchers reported that people who are obese experience less of a response to food in the reward centres of the brain, which may contribute to over-eating. Repeatedly eating foods with high levels of calories (called “energy dense” foods) has also been shown to lead to brain changes that reduce reward response in rats. The researchers wanted to see if a similar thing happens in humans, by looking at whether regularly eating ice cream reduces the brain’s pleasurable reward response to an ice cream milkshake.
What did the research involve?
The researchers recruited 151 adolescent volunteers who were not overweight. They asked them how often they ate ice cream, and carried out brain scans while they drank either a tasteless solution or an ice cream milkshake. They then looked at whether the volunteers who ate ice cream frequently showed less brain activity in the reward centres of the brain when drinking the ice cream milkshake.
The study excluded any individuals who were overweight or had reported binge eating in the past three months, as well as any who had used illegal drugs, took certain medications, had a head injury or a mental health diagnosis in the last year. The volunteers completed standard food questionnaires about their eating habits over the past two weeks, including how often they ate ice cream. They also answered questions about food cravings and how much they liked certain foods, including ice cream. The volunteers also had their weight, height and body fat measured.
Volunteers were asked to eat their meals as usual but not to eat anything for five hours before the brain scan. The researchers then gave them either a sip of chocolate ice cream milkshake or a tasteless solution, and monitored the activity in their brain. Each participant received both drinks in a randomised order. The researchers then looked at what happened in the brain during each drink, and whether this varied depending on how much ice cream the volunteer usually ate. They also looked at whether body fat or energy intake from other foods influenced the response.
What were the basic results?
The researchers found that when the volunteers drank the ice cream milkshake, it activated the parts of the brain involved in giving a pleasurable “reward” feeling. Volunteers who ate ice cream frequently showed less activity in these pleasurable reward areas in response to the milkshake. Percentage of body fat, total energy intake, percentage of energy from fat and sugar, and intake of other energy-dense foods were not related to the level of reward response to the milkshake.
How did the researchers interpret the results?
The researchers concluded that their findings show that frequent consumption of ice cream reduces the “reward” response in the brain to eating the food. They reported that a similar process is seen in drug addiction.
The researchers also said that understanding these sorts of processes could help us understand how changes in the brain may contribute to, and help maintain, obesity.
This brain-scanning study suggests that the brain’s pleasurable reward response to ice cream decreases if it is eaten frequently. There are some points to note:
- The study only included healthy adolescents who were not overweight. Its results may not be representative of overweight or older individuals.
- The study only tested one food, so the results may not apply to other foods.
- Volunteers’ eating habits were only assessed for the past two weeks, and these may not be representative of their long-term eating habits.
- The study did not look at any other food with a discernable taste, only a “tasteless liquid”. It would have been interesting to see whether the reward response with tasting other foods, including less energy-dense foods, also diminished over time.
- News reports claimed that this study shows that ice cream is “as addictive” as illegal drugs, but this is not the case. While the reduced brain reward seen with frequent ice cream eating was reportedly similar to that seen in the use of addictive drugs, the study unsurprisingly did not directly compare brain responses to ice cream and illegal drugs, or their addictive potential.