Milan Valyear has a Master’s degree in psychology from Wilfrid Laurier University and is currently a doctoral candidate at the Center for Studies in Behavioral Neurobiology at Concordia. He studies addiction in the lab of Dr. Nadia Chaudhri and is particularly interested in the neural systems that control how cues in the environment trigger relapse. Using cutting-edge neuroscience tools, he is able to silence specific neural pathways when rats are presented with alcohol cues and observe how they respond.
Why do people become more interested in sugar during the holidays?
For many people, the holidays are a time to indulge their sweet tooth. As consumption increases, so too does our interest in sugar. A Google trend analysis for the search term “sugar” in Canada reveals that, while interest in sugar has grown over time, it consistently spikes in December every year.
What can this simple analysis tell us about the psychology of indulging in sweet treats over the holidays?
Google trends normalizes this analysis so that the number of searches over time are a percentage of the number of searches conducted during the month with the highest number of searches overall. The spike in sugar searches in December of 2007 was approximately half the size of the spike in December of 2017, which is the largest spike on record.
This simple analysis raises a few questions. Why have search rates increased over time? And why do we become more interested in sugar in December?
One simple explanation for the increase in sugar searches over time is that more people are performing Google searches, so this trend reflects an increase in searches overall, rather than a specific increase in sugar interest. A general increase in Google searches over time likely contributes to the trend for growing interest in sugar over time, but it does not seem to completely explain the trend.
If an increasing number of people were performing Google searches over time, we should see an increase in searches for any search term.
As an arbitrary comparator, we can observe searches for “kale” over time. Despite the recent interest in eating healthy and consuming so-called superfoods, Google searches for “kale” do not seem to increase linearly over time. Kale searches begin to increase in 2010, plateau around 2014, and potentially wane thereafter.
Another discrepancy between kale and sugar searches is that kale searches do not spike around December. The hypothesis that sugar search trends reflect general increases in Google searches, whether over time or in December, does not receive support by the trends for our comparator search term kale. This discrepancy in sugar versus kale search trends calls for further analyses, or at least speculation.
Why do we become more interested in sugar in December? The most obvious reason for our increased interest in sugar around December is that it coincides with the holiday season. Around this time sweet treats are plentiful and people likely become more interested in the effects of sugar consumption on health, sugar contents of different foods and sugar-related recipes.
If we assume that interest in sugar grows in December because of the holiday season, we should also expect sugar searches to spike in other months in which holidays occur. This does in fact appear to be true. An October spike precedes the December sugar searches, and a trailing spike appears in March. The October spike coincides with Halloween, and the March spike occurs close to Easter.
There is some satisfaction in explaining annual spikes in sugar searches by their companion holidays, but what exactly is it about the holidays that piques our interest in sugar? Yes, sweet treats are undoubtedly more plentiful around the holidays and thus easier to consume, but might we also believe that they taste better?
In addition to sugary foods being abundant around the holidays, there are also specific foods that are exclusively available during certain holidays. Consider candy corn at Halloween, candy canes at Christmas and chocolate eggs at Easter. Is it possible that we value these treats because they are only available once a year, and thus our interest in these foods increases when they are available?
There is a considerable amount of rodent literature showing that when foods are made available infrequently, rats will increase their consumption during periods of availability. Rats that have unlimited access to standard rat food and water will consume significantly more vegetable shortening1, sugar2 or even OreoTM cookies3 when these additional foods are made available intermittently as compared to when they are constantly available.
It has even been argued that these patterns of elevated consumption of tasty, but infrequently available foods, resembles binge eating in humans4. As a note, this pattern of increased consumption of foods that are less accessible is also true for alcohol, which was discovered at Concordia5.
In addition to consuming intermittently available foods in larger quantities, rats are also more motivated to consume these foods. For example, rats that have access to vegetable shortening for one hour three times a week, consume significantly more in that one hour than do rats with access to vegetable shortening for one hour every day.
Then these two groups of rats are given the opportunity to press a lever to earn small amounts of vegetable shortening. The number of lever presses required to earn a delivery of shortening increases with every successful delivery earned. In other words, the cost — in lever-presses — increases.
Rats with a history of intermittent access to shortening will ultimately perform significantly more lever-presses for a single delivery of shortening than will rats with a history of daily access to shortening6. The rats with intermittent access will pay a higher price for the same vegetable shortening, perhaps because they value it more, than rats with daily access.
There are a variety of reasons why we become more interested in sugar around the holidays and it can be difficult to understand what fluctuations in Google searches tell us about the people performing the searches.
I have made the argument that increased sugar searches during the holidays may reflect an increased value we place on sweet foods that are only available during certain times of the year. This argument is very speculative, but fun to entertain.
At the very least we can be sure that people become more interested in sugar during the holiday months, when sweet treats are plentiful, and that we may place a high value on these treats because they are only available during the holidays.
1. Corwin, R. L. W. et al. Limited access to a dietary fat option affects ingestive behavior but not body composition in male rats. Physiol. Behav. 65, 545–53 (1998).
2. Eikelboom, R. & Hewitt, R. Intermittent access to a sucrose solution for rats causes long-term increases in consumption. Physiol. Behav. 165,77–85 (2016).
3. Boggiano, M. M. & Chandler, P. C. Binge eating in rats produced by combining diet with stress. Curr. Protoc. Neurosci. Chapter 9, Unit 9.23A (2006).
4. Corwin, R. L. W. & Babbs, R. K. Rodent models of binge eating: are they models of addiction? Inst. Lab. Anim. Res. J.53, 23–34 (2012).
5. Wise, R. A. Voluntary ethanol intake in rats following exposure to ethanol on various schedules. Psychopharmacologia 29, 203–10 (1973).
6. Wojnicki, F. H. E., Babbs, R. K. & Corwin, R. L. W. Reinforcing efficacy of fat, as assessed by progressive ratio responding, depends upon availability not amount consumed. Physiol. Behav. 100, 316–21 (2010).