Your nose is running, your head hurts, and you feel like you’re coming down with a cold. As you settle on the couch for a sick day, you can’t help but reach for the snacks. But why do you crave sugary treats and carbohydrate-loaded comfort foods when you’re sick? Let’s explore the science behind this phenomenon.
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Fuelling the Immune System
When sickness strikes, our immune system kicks into high gear, requiring additional energy to combat invaders. This increased activity leads to a rise in our metabolic rate, energy demands, and nutritional requirements. Sugary treats and carbs provide quick sources of energy, satisfying this increased demand.
But while a high-sugar diet during illness may meet these increased metabolic demands, it could also exacerbate the immune and inflammatory response, potentially hindering recovery. In the long term, high-sugar diets promote chronic inflammation, disrupt gut microbiota composition, and are associated with chronic diseases. To maintain a well-functioning immune system, it’s important to aim for a balanced intake of fruits, vegetables, fiber, protein, and low-glycemic carbohydrates.
The Stress Response
Being sick puts stress on the body. Acute mild or intense stress, like when we’re sick, triggers the release of “flight or fight” hormones such as adrenaline and cortisol. These hormones mobilize stored energy to meet increased demands but can also curb appetite. Prolonged stress can disrupt energy balance, cause nutritional deficiencies, and alter gut and brain functions. This can lower a person’s threshold for craving sugar and salt, increasing their preference for energy-dense foods.
The stress hormone cortisol can also heighten the preference for high-calorie comfort foods, temporarily alleviating stress.
The Brain’s Reward System
Comfort foods activate the brain’s reward system, leading to the release of feel-good neurotransmitters like dopamine and serotonin. However, the “sugar rush” is often short-lived and can result in decreased alertness and increased fatigue within an hour of consumption.
The link between carbohydrates (which the body converts to sugar) and serotonin can be traced back to 1971 when researchers found elevated tryptophan levels (serotonin’s precursor) in rats’ plasma and brains after a carbohydrate-rich diet. Subsequent studies in humans established connections between carbohydrates and mood, particularly in relation to obesity, depression, and seasonal affective disorder. Therapies that enhance serotonin have been shown to reduce carbohydrate intake.
Remarkably, around 90% of serotonin production occurs in the gut. The vast microbial population in our gut influences immunity, metabolism, and appetite. Recent studies in mice have even identified specific microbes linked to sugar binges following antibiotic treatment.
Some People Eat Less When They’re Ill
Not everyone craves sugar and carbs when they are sick. Some people eat less for a few reasons:
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They have a reduced appetite. While ghrelin (the “hunger” hormone) levels might initially rise, prolonged illness can suppress appetite due to nausea, fatigue, and discomfort. Critically ill patients often have reduced food intake and are at risk of malnutrition.
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Metabolic adaptation. The body might slow down specific metabolic processes to conserve energy, reducing overall calorie requirements.
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Altered taste perception. Taste plays a crucial role in both appetite and energy intake. When we’re sick, alterations in taste and smell are common symptoms, as seen with COVID.
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Consuming fluids like water, tea, or broths might be more appealing and manageable than solid foods. These fluids provide hydration but contribute minimally to calorie intake.
Understanding why our bodies crave carbs and sugar when we’re sick helps shed light on the complex interplay between our physical and emotional well-being. By making mindful food choices, we can support our immune system, manage stress, and nourish our bodies during illness.
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