It’s a question many of us will have asked ourselves at some point. Whether it’s snacking on crisps or chocolate, or getting in pizza or Chinese, there are some foods which just seem to leave us craving more. As it turns out, in many cases science offers us an explanation.
Food has been an important part of our survival for a very long time, forever in fact, and so the motivational systems of the brain are highly aware of it. The body has sensors in the mouth and gut which measure the nutritional content of foods, and then the level of motivation is set by the brain based on this information via dopamine release in the nucleus accumbens, the reward centre of the brain. Addiction is often associated with excessive levels of dopamine in this region, which can lead to self-destructive behaviours.
As you probably already expected, junk food tends to be the most addictive group of foods. When people were asked to rank a series of foods by order of addictiveness, top answers included chocolate, chips and pizza. When the nutritional content of these foods were analysed, it was found that the fat content and the glycaemic load – a measure of the amount of carbohydrate is in the food and how quickly blood glucose is raised – were strongly associated with the potential for addiction. What this means is that we are drawn to foods that are concentrated in calories and are rapidly digested.
Intense sweetness, whether from sugar or artificial sweeteners, produces an Indication of physical craving
A number of experiments have shown that intense sweetness, whether from sugar or artificial sweeteners, produces an indication of physical craving. In fact, sweetness has been shown to surpass cocaine as a reward in laboratory animals. As it turns out, an analysis of over 100 articles revealed that humans produce opioids as a derivative of digestion of excess sugars and fats. Opioids are the chemically active ingredient of many drugs known to be addictive, such as heroin and cocaine. Testing using the opiate blocker naloxone reduced the level of interest in sweets compared to others who had not been treated.
There is also a correlation between overconsumption of fat and brain systems which stimulate the intake of fat when activated. Rats given fat-rich foods did not show opiate withdrawal symptoms when treated with opiate blockers or during fasting. So, although fat rich foods seem to result in addiction like effects, overeating fatty foods affects the opioid systems in the pleasure centres of the brain differently to sugar.
There are also elements of flavour which make food moreish. The ‘fifth taste’ umami, from the Japanese word for ‘deliciousness’ or a pleasant savoury taste, arises from the presence of the amino acid glutamate. This is the basis of monosodium glutamate, an additive which is seen in many processed foods, where it used to enhance meaty and savoury flavours. Umami can also be the result of ribonucleotides, which occur naturally in many foods. Umami is a marker of protein in food, which could explain why we seek it out. It is possible that it has evolved so that we could get suitable levels of protein in our diet. Combining ingredients with different umami compounds results in a greater flavour than the individual components, which may explain why dishes such as Bolognese with cheese or cheeseburgers with ketchup may be your flavour of choice, as all three amplify the umami of the other parts to create a moreish taste.
So, as it turns out, here are many factors that play into our love of certain foods, and while some of it is psychological, there are also physical responses at play. Next time you find yourself reaching for another cupcake, don’t feel guilty. After all, it’s down to science.