How Does High-Sugar, High-Fat Food Affect Short-Term Memory in Teenagers?

Introduction - Aim and Wider Purpose

Carbohydrates make up a significant portion of our diet. Many foods in our daily diets include carbohydrates: rice, pasta, roti, cakes, bread and so on. In India, over 75% of the diet consists of carbohydrates, 25% above the WHO's recommendations [1]. Sugars are a subset of carbohydrates that are easier to digest and are linked to increased morbidity and instability in blood sugar.

What Are Carbohydrates?

Carbohydrates are organic compounds composed of carbon, hydrogen and oxygen. Some common examples of carbohydrates are glucose, maltose, lactose (found in milk), starch, and glycogen.

Alongside proteins and fats, carbohydrates are an essential macromolecule found in food. Various enzymes digest carbohydrates, facilitating the breakdown of bonds between the molecules and releasing energy. Carbohydrates are also crucial for making neurotransmitters and can promote the release of serotonin and dopamine, for example. This makes carbohydrates a critical dietary component for brain function [2].

What Is Working Memory?

Working memory is a subcomponent of memory that holds information for short periods of time, typically under 30 seconds [3]. According to Attkinson and Shiffrin, an individual can hold up to 7 items in their working memory, which is also why phone numbers in the USA are 7 digits long [4].

Working memory is critical for performing well on exams, studying and spatial navigation [5]. This makes good working memory a priority for teenagers developing their cognitive skills in school.

Working Memory And Carbohydrates

Carbohydrates act as the most significant component of the diet of many individuals, and it is vital to understand the repercussions of eating carbohydrates, particularly before a big event/exam. The body breaks down carbohydrates in the metabolic process of catabolism. Carbohydrates are broken down to glucose, which can enter the bloodstream and travel to the brain. Glucose can also permeate the blood-brain barrier and reach the midbrain and prefrontal cortex, two critical areas for working memory. In the midbrain, glucose increases levels of dopamine and serotonin, which can improve attention and focus. On the other hand, too much glucose can lead to excess dopamine and adrenalin, impairing focus and exciting the brain. Too much glucose also stimulates the release of insulin, which causes hypoglycaemia and subsequent impaired function of the brain, as glucose is the primary nutrient used by the brain.

Study Implications

The implications of this study can improve nutrition and mood in teenagers, a population in a critical development period. Teenagers often neglect their nutrition despite being in demanding and high-pressure situations, such as exams, that require optimal working memory.

This study investigates the role of cookies in working memory, building the foundation for further research on the intersection of nutrition and psychology.

Aim

This study aims to investigate the correlation between carbohydrates and memory, a macromolecule in the diet and a cognitive function essential for daily activities [6]. More and more of our daily chores are becoming dependent on short-term memory storage, and if there is a correlation between a specific food type and its influence on our memory, this could benefit many students and young adults who have to take exams or work on concurrent tasks.

The objective of this study to look at the effects of carbohydrates on short-term memory will be divided into 3 sections:

1. The confidence-accuracy trade-off: How confident are people about making a choice, and are they willing to respond when they are not confident?
2. Accuracy between a control group and experimental group, who will be given a high-sugar, high-fat cookie before testing
3. The impact of eating breakfast and the type of breakfast eaten.

Background Research

It was essential to first establish the definition of short-term memory. The model explored was the multi-store model developed by Attinkson and Sheriffron due to the simplicity and translational validity of this model [3]. The multistore model of memory describes memory as a three-step process:

1. Sensory memory is where your senses register information when you pay attention.
2. Short-term memory: the registered information enters this vast store and stays there for approximately 18 seconds. According to this model, short-term memory has a capacity of 7 +-2 information items.
3. Long-term memory: If memory is rehearsed/practised, it enters permanent storage with potentially unlimited capacity.

Short-Term Memory: The Scientific Evidence

This section summarizes research surrounding this short-term memory to provide a more holistic evaluation of my research and results.

Carbohydrates, and sugar in particular, have been linked to the decline of brain function, and many experts advise the avoidance of high-sugar foods to combat the symptoms of ADHD [7]. A study by Charité University Medical Center in Berlin conducted by George Sachs PsyD studied the brains of over 140 healthy individuals between the ages of 50 and 80. The results indicate that “higher blood sugar readings performed worse on the memory test than those with lower blood sugar levels. Also, imaging revealed a smaller hippocampus was found to be among those with higher blood sugar levels.” [8]

The results conclude that eating carbohydrates reduces short-term memory performance. Nonetheless, the study was conducted in adults with distinct dietary needs to teenagers. Hence, our study is critical to understanding the role of high-sugar foods in teenagers.

A study conducted by the psychology department of Tufts University in Medford, Massachusetts, by Dr Holly Taylor experimented between the variables of a low-carb diet vs a low-calorie diet, and the results indicate that “Low carb dieters showed a gradual decrease in memory tasks compared with low-calorie dieters.”[9] It was also noted that low-carb dieters performed better in attention vigilance tasks compared to low-calorie dieters. Dr Taylor added ““The data suggest that after a week of severe carbohydrate restriction, memory performance, particularly on difficult tasks, is impaired,” Although this study was an extreme measure, the base idea remains intact with my hypothesis, and I am hopeful that I was able to reflect these results into my replication.

Harvard Health also published a synthesized guide towards food that declines memory and confirms that after much research, food correlates with memory in general [10]. The list of foods that are beneficial to eat, including fruits, fish (indicating protein), and carbohydrates, are missing from this detailed analysis, which implies that either do not have a significant massive impact or are too complex to quantifiably measure- both these ideas would weaken my argument however, I am confident that I will have some results to compare and find visible patterns.

There have also been correlations drawn between diabetes and loss of memory- “Memory loss in diabetes, especially type 2, can be a short-term problem brought on by too low or high blood glucose levels.” However, this, in my view, is a stretch of a claim because diabetes is typically caused at an older age- where memory loss is already associated. This is not linked to my research, so I did not spend too long surfing through this approach; however, it was interesting to note the existing claim around blood glucose level and short-term memory.

In contrast, research conducted by a group at Turfs concluded that “when you remove carbohydrates for three weeks from the diet of people who have depended on them for decades, you get some short-term memory loss,” among other claims, such as becoming moody [11]. This is a direct counterclaim to my hypothesis. However, my focus is on short-term benefits or disadvantages. Hence, the findings of Turfs are not directly comparable with the timescale I investigated. Nonetheless, the outcome measures provide some overlap, demonstrating the impact of carbohydrates on memory and mood.

Overall, the evidence linking carbohydrates with memory performance and mood is strong, indicating that my research question is well positioned within the existing knowledge, focusing on a critical sub-population of teenagers. The literature that has been crucial in supporting my methodology is discussed in the following section.

Experiment Methodology

This experiment recreated the 1959 study by Peterson and Peterson [12]. It also investigated short-term memory storage using trigrams. With a short delay or distraction, the participant’s memory recall of the trigrams was tested.

The Variables were as follows:

• Independent Variable: carbohydrates eaten
• Dependent Variable: number of trigrams recalled
• Control Variables: time allocated to memorise, time allocated to write, time of the day study conducted, instruction provided, age of participants

Subjects

This study was a lab experiment with 27 participants (16 participants in—the control group, 11 participants in—the experimental group), an opportunity sampling of high school students. It was conducted during the first period (between 7:40 and 8:30) to exclude confounding the effects of breakfast by foods eaten later in the day.

Procedure

The experimental group was given a set of cookies to eat at 7:45AM, and the experiment started at 8:10AM (25 minutes after eating the high-sugar, high-fat cookie). Although complex carbohydrates take roughly 24 hours to digest, the sugar available in the cookie can reach the bloodstream quicker within 25 minutes. Within the 25-minute waiting period, the control group was tested.

The test lasted 20 minutes for both groups. The participants were shown four slides, each with 10 words. The first two consisted of trigrams, and the last two had words, with one slide containing a semantic field of food (chocolate, tasty, sweet, sugar).

After collecting the results, the participants were debriefed and told the true purpose of the study. They were then asked for consent to include their results in the study, according to ethical guidelines. Cookies were offered to the control group after testing.

Results

Every subject's four outcome points were analysed, and their results were grouped according to whether they belonged to the control or experimental group. The first trial was excluded, as this formed a trial run to get a cookie and had significantly lower mean recall accuracy, ensuring the participants understood the task.

Accuracy: Control vs Experimental Group

The results indicate that the experimental group ate more than the control group.

Specifically, the experimental group's decline in the S1 frequency was 12% and 8% in the S2 frequency.

Confidence-Accuracy Trade-off: Control vs Experimental Groups

Next, we investigate the guessed vs accurate ratio between the control and experimental groups. The idea was to check if eating carbohydrates would impact the focus, making participants less attentive and more likely to guess the response rather than recall it from their short-term memory. Indeed, we found that the experimental group were 38% more likely to guess, even though the guesses were less accurate.

Impact of Breakfast on Short-Term Memory

As the testing was carried out in the morning, we wanted to separate the participants who had had breakfast from those who had not. This was because breakfast can contain carbohydrates, which may disrupt the effect of our experimental intervention.

We found that participants in our control group, so those who had not received a cookie but had had breakfast in the morning, were more accurate (mean =7.4) than those in the control group who did not (mean = 7.1).

This meant that we studied the following groups:

1. Non-carb breakfast + no cookie (control)
2. Non-carb breakfast + cookie (experimental)
3. Carb Breakfast + no cookie (control)
4. Carb Breakfast + cookie experimental)

As an additional analysis, we compared the types of foods that people ate for breakfast and found that those who had eaten non-sugar foods performed better than people who had not had breakfast.

Therefore, eating a low-sugar breakfast provides an advantage over not eating breakfast, or eating a high-sugar breakfast. This distinction is interesting, as it would support the role of long-release carbohydrates in brain function and short-term memory [12]. An additional factor that could explain this finding is the time since eating the carbohydrate and performing the task.

Experimemt evaluation

The experiment successfully answered the question and provided a clear correlation between high-sugar intake and immediate short-term memory testing. Although we set out to answer whether carbohydrates impact short-term memory, the choice of experimental intervention (a cookie) did not enable us to isolate carbohydrates alone. The cookie contained a lot of sugar and fat, which may confound our results. When combined with the high and low-sugar breakfast outcomes, prior literature on the role of simple vs complex carbohydrates [12] and the metabolic role of glucose and insulin in the brain, our results may best be interpreted through a focus on sugar rather than carbohydrates.

To validate our results, the following variables would need investigation:

• Increasing the time between eating the cookie and memory testing will allow further absorption of the carbohydrate snack.
• Testing students in isolation to avoid copying and observation effects.
• Some participants were psychology students familiar with the Peterson and Peterson study and the idea. Therefore, selecting a sample more representative of the general population would increase the generalisability of the results.
• The sample size was small, reducing the generalisability of the outcomes.

There are various external factors, such as learning needs, dyslexia/ADHD, hours of sleep, and whether students exercise in the morning (some teams train before school). All of these health conditions could affect the results.

Summary: Carbohydrates Impair Short-Term Memory in Students

To conclude, eating carbohydrates negatively impacts short-term memory in students, although the mechanism through which this occurs remains to be studied.

Our study provides preliminary evidence and strengthens the understanding of diet's role in teenagers' short-term memory. By reducing high-sugar, high-fat intake and eating a low-sugar breakfast, teenagers have a high chance of improving their working memory, which will benefit their academic and early professional accomplishments. Although we did not examine the impact of sugar and carbohydrates on longer-term memory, evidence suggests that improvements in short-term memory do translate to increased long-term memory and hence the retention of information in academic settings [13].