Emotions and eating behaviour – Part II

Welcome back, in the last lecture we learned that mood and emotions could influence food choice and today I would like to talk about whether eating a particular food or a combination of foods can alter your mood. We will look into sensory and hedonic effects, associated social context, as well as physiological and neurochemical changes due to food intake or due to the intake of specific macro or micronutrients. Dr. Macht, the researcher I mentioned in my earlier lecture also proposed five pathways how food affects mood and these

are: Associative effects Sensorial-affective effects Energetic effects Neurochemical effects and pharmacological effects What he meant by “associative effect” is the influence of our associations or opinions, possibly from past experiences with the to be ingested food. If I taste a cake that reminds me of my grandmothers’ strawberry cake I might think about the summer vacations I spent at her house which in turn will make me happy, if it was a happy experience. In general, a food can have a positive or negative associative effect.

Another example for associative effect is that, if we consider French fries to be bad for our body or our diet but we happen to eat it (maybe because nothing else is available or offered) then this might decrease our mood. The sensorial-affective effect describes how food impacts our sense of taste which then influences our mood. The sensation of sweetness for instance is innately pleasant whereas bitterness is innately aversive. Babies show a positive affective reaction when exposed to sweet taste solutions. Palatability in general can positively influence our mood. Another sensorial aspect that is often discussed when talking about the effect of chocolate on mood, is the hedonic aspect.

Chocolate in itself, leaving possible neurochemical reactions aside for now, has hedonic or pleasurable properties. Before the nutrients of chocolate even reach the blood stream or the brain, we feel a positive sensorial-affective reaction. And the more I will talk about chocolate, the more you will probably think about chocolate and the more I will have caused what I just previously described as an associative effect. Simply by thinking about chocolate your mood might have changed, hopefully to the better. But let’s move on to the third mechanism. The energetic effect simply describes the mood increase if a hungry organism (applies for both animals and humans) ingests food. Most animals including human beings are alert and some even irritable when hungry.

After something to eat however they become calm, relaxed and the mood is improved. Chronic severe food restriction can even lead to depression and constant negative emotional state. The neurochemical effect is a controversially discussed topic. Research has shown that eating activates the dopamine and opiod neurotransmitter system. Since you have been introduced to these systems involved in reward processes in another lecture I will not focus on them but now give you some interesting examples. Earlier I mentioned the innate preference for sweet foods. Another plus side on sweet and fatty foods is the fact that their ingestion alleviates crying and other behavioral signs of distress in babies. Research found that this is also the case for non-nutritive sweeteners which don’t contain calories.

Thus, your baby not only stops crying because it is no longer hungry but also because it is tasting something sweet. In regards to the neurochemical effect it is also said that a carbohydrate rich meal through various pathways increases serotonin levels in the brain. This effect caused an extensive discussion on meal composition and the effects of nutrients on mood and stress. In general, there is evidence that people feel more calm and relaxed after snacks or meals rich in carbohydrate but free of protein than after protein-rich meals. There is also evidence that high-fat meals increase fatigue and reduce attention.

Nevertheless, the extent of these effects seems to depend on individuals’ differences, in susceptibility to nutritional effects on mood, emotion and aspects of brain function. What should also be mentioned is the increasing interest in nutrients such as vitamins, minerals, fatty acids and amino acids and their relationship to mood. One study for instance found a positive effect of a flavonoid-rich blueberry drink on mood in children and young adults, however, future studies in that area are definitely needed in order to recommend intake on a population level. The last effect described by Dr. Macht is pharmacological effect.

The classical and most known example is the effect of caffeine – found in coffee- or theobromine – found in green or black tea - the intake of either has been shown to increase alertness and mood. This five described mechanisms do not happen at the same time during our food intake. In fact, this graph shows the five effects on mood from a time perspective. As you can see, physiological effects such as the one based on energy intake, neurochemical or pharmacological processes can of course only happen after ingestion, while associative effects can even happen before ingestion. Taken together, I hope today’s lecture showed you the different pathways of how what you eat might change your mood.

On a last note, it is important to mention that the impact of food and drink also always depends on the person’s initial state, expectations and attitudes. And these cognitive aspects and their importance in determining food choice and eating behavior will be discussed in further lectures.