Can your breakfast make or break your grades?
You’ve probably heard the saying ‘you are what you eat’ – but have you ever considered that your memory may be as good as the food you eat?
Food has a profound influence on the functioning of our brains. This is especially clear when we consider the effects of the "Western Diet", a pattern of eating characterised by high saturated fat and refined sugar. The Western Diet contributes to chronic illnesses such as obesity, hypertension and diabetes (Hariharan, Vellanki, & Kramer, 2015), but it is also increasingly recognised that excessive consumption of saturated fat and sugar can affect the hippocampus, the part of our brain essential for learning, spatial orientation and memory (Kanoski & Davidson, 2011).
Some evidence that a poor diet affects cognitive function comes from studies on rats, which were fed the rodent equivalent of junk food - a diet high in fat and sugar - and showed reduced performance on a spatial task after just three days (Kanoski & Davidson, 2010). In humans, prolonged saturated fat intake is linked to impaired memory performance, and reduced cognitive speed and flexibility in both middle-aged adults (Kalmijn et al., 2004) and young females (Leigh Gibson, Barr, & Jeanes, 2013), although impairments can emerge almost immediately (Attuquayefio, Stevenson, Oaten, & Francis, 2017).
Whereas most of the previous studies on humans that have explored the link between the Western Diet and cognition were correlational, the study by Attuquayefio and colleagues provided causal evidence that high saturated fat and refined sugar diets impair proper brain functioning. In this experiment, the participants with a normal BMI and who generally consumed foods low in saturated fat and refined sugar were invited into the lab to consume one of two breakfasts: either an unhealthy one (with excessive amounts of saturated fat and refined sugar), or a healthier alternative (with a markedly lower fat and sugar content). Participants had the same breakfast (healthy or unhealthy) for four days in a row. They completed some cognitive ability tests on the first day and the last day, so that the effects of breakfast type could be assessed.
Those who consumed the unhealthy breakfast, the experimenters found, showed worse memory retention at the end of the experiment, although their logical memory performance (which is not dependent on the hippocampus) was not affected. Moreover, participants who had the unhealthy breakfast were less sensitive to the satiety signals their body was giving them, and they needed to eat significantly more food to shift their hunger and fulness ratings, compared to the amount of food they needed to shift these ratings on the first day of testing.
This is not to say that those who had the high-calorie, unhealthy breakfast just consumed more calories during the four-day period – food diaries which the participants kept throughout the study duration revealed that both groups ate about the same number of calories during the course of the experiment. But those in the unhealthy-breakfast group compensated for their caloric surplus by reducing the number of carbohydrates they ate for the remainder of the day, yet still ended up eating more saturated fats overall, which is what ultimately, the researchers speculate, led to their poorer memory performance on day four.
So having a breakfast (and potentially other meals too) full of saturated fats and refined sugars (I’m looking at you, full English breakfast), can affect how well you’re able to remember things. And these effects can manifest themselves very quickly. Poorer memory may, in turn, affect your performance on school tests. Indeed, evidence suggests that feeding children junk food substantially reduces their reading scores (Tobin, 2013), their maths scores (Li & Connell, 2012) and their general academic achievement (Kristjánsson, Sigfúsdóttir, & Allegrante, 2010). It is also not far-fetched to hypothesise that poor quality food may affect university students’ academic performance or even test-unrelated job performance. The take-home message is simple – if you want to achieve, you must fuel your body with nutritious food, not junk!