Ever found yourself wondering whether that late-night bowl of pasta or sweet treat is helping or hindering your sleep? The answer isn’t straightforward—it all depends on the type of carbs you’re eating and when you’re eating them.
Some carbohydrates, particularly simple carbs, can mess with your sleep quality, while others—like complex carbs—might actually help you get better rest. The way your body metabolises these carbs plays a significant role in your sleep cycle. Let’s break it down.
Understanding Carbohydrates
Carbs are found in a wide range of foods, from whole grains and fruit to yoghurt and even salad dressing. No matter the source, all carbohydrates break down into glucose, which your body uses as energy. However, different types of carbs are processed differently, affecting everything from blood sugar levels to metabolic function.
Metabolism is the sum of the processes that keep your body running—converting food into energy, repairing tissues, creating new cells, and eliminating waste. Once carbs are broken down into glucose, your bloodstream absorbs and transports it to your cells, where it’s either used for immediate energy or stored for later.
How quickly this process happens depends on whether you’re consuming simple or complex carbs.
Simple vs. Complex Carbs: What’s the Difference?
- Simple carbs (found in sugary snacks, white bread, and processed foods) are broken down quickly, causing rapid spikes and crashes in blood sugar levels.
- Complex carbs (found in whole grains, vegetables, and legumes) break down more slowly, providing a steady release of glucose and keeping blood sugar stable.
Why does this matter for sleep? Rapid blood sugar spikes from simple carbs can lead to energy crashes and increased hunger, while slow-digesting complex carbs help regulate hormones and promote metabolic balance.
How Simple Carbs Disrupt Sleep
Eating simple carbs before bed triggers hormonal and physiological changes that can interfere with your sleep, such as:
- Blood sugar fluctuations – Simple carbs cause a sharp rise in blood sugar, followed by a sudden drop (reactive hypoglycaemia), which can lead to restless sleep and frequent night-time awakenings.
- Melatonin disruption – Melatonin, the hormone that helps you sleep, is affected by glucose levels. High blood sugar can reduce glucose tolerance and insulin sensitivity, increasing inflammation and making it harder to stay asleep.
- Cortisol spikes – When blood sugar crashes, your adrenal glands release cortisol (the stress hormone) to bring it back up. High cortisol levels at night can make it difficult to fall and stay asleep.
- Increased urination – High blood sugar forces your kidneys to work harder to filter excess glucose, potentially leading to more night-time bathroom trips.
How Complex Carbs Improve Sleep
Complex carbs, on the other hand, are a better choice before bed. Because they digest slowly, they help maintain stable blood sugar levels, reducing sleep disturbances and promoting deeper, more restorative sleep.
A study comparing simple vs. complex carbs found that those who ate simple carbs had higher cortisol levels and a higher sleeping metabolic rate, suggesting their bodies had to work harder during sleep. Another study found that participants who consumed more complex carbs (like whole grains) had a 3.26 times higher chance of sleeping well.
What to Eat (and When) for Better Sleep
Carbs aren’t the enemy. In fact, very low-carb diets (such as keto or paleo) can negatively impact sleep by reducing deep sleep and REM sleep.
The key is choosing the right carbs at the right time. Some good options include:
- Whole grains (brown rice, whole-wheat bread, quinoa)
- Prebiotic carbs (oatmeal, underripe bananas, apples, wheat bran)
- Fruit (despite containing simple sugars, fruit also has fibre to slow glucose release)
- Root vegetables (beets, parsnips, turnips)
- Legumes (lentils, black beans, chickpeas)
Timing matters, too. Eating too close to bedtime can delay sleep onset, reduce sleep efficiency, and interfere with REM and deep sleep. Try to finish eating at least three hours before bed to allow for proper digestion, giving your body a chance to focus on rest and recovery.
The Takeaway
If you’re going to eat carbs before bed, opt for complex carbs to support better sleep. Avoid sugary snacks and processed foods that can cause blood sugar crashes and disrupt your sleep cycle. And, whenever possible, give your body enough time to digest before heading to bed. Small changes to your evening meals could make a big difference in the quality of your sleep.
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