Does Eating Sugar Late at Night Cause Nightmares?

Eating sugar and other foods change the chemistry of your brain and body. Learn how that can affect our sleep and dreams.

Each day, many Americans eat too much sugar. This can cause a variety of health problems—from heart disease to diabetes—and also make you feel tired. With these effects in mind, you may be wondering how sugar and other foods can affect your sleep.

Many people believe foods, including sweets, can cause nightmares. A 2015 study in Frontiers of Psychology, for example, showed that almost 20% of people believed that certain foods or late meal times could affect their dreams. These study participants most commonly blamed dairy and sugar for their nightmares, though they also thought spicy food could be linked.

Scientists are not certain why specific foods might affect dreams, but they have some ideas. One hypothesis is that the chemicals in some foods do cause different kinds of dreams, as many people believe. Alternatively, people may be intolerant or have reactions to some foods. These reactions could affect your sleep quality and, therefore, your dreams. Finally, people may just be falsely linking the food they eat and their dreams later that night.

Scientists believe sugar may or may not cause nightmares by changing your body. Learn more about how sugar can affect your sleep and what kind of nighttime snacks you should eat.

What Is Sugar?

When you think of sugar, you may think of the cane sugar in sweets. However, sugars are actually a type of carbohydrate⁠—a "simple" carbohydrate. This means that sugars are made of one or a few chemical subunits. If the chains of the subunits are longer, these carbs are called "complex."

When you digest food, your body breaks down carbohydrates into sugar subunits. Then, you transport these subunits in your blood to cells across your body, where the cells can use it for energy. Because they are easier to digest, simple sugars like sweeteners raise your blood sugar levels quickly. However, complex carbs like in grains raise your blood sugar level at a slower rate.

The Glycemic Index (GI) is a measure of how fast sugar subunits enter your blood—a sign of how long it takes to digest the carb. According to the NIH, simple sugars enter the blood quickly, so they have high GIs. Complex carbohydrates, on the other hand, have low GIs because they take more time to break down.

Blood Sugar Can Change Your Body Chemicals While You Sleep

Research shows that both the amount and GI of carbohydrates you eat can affect your sleep. For example, a 2021 Nutrients analysis showed that the number of carbs you eat can change how long you stay in different sleep stages. Meanwhile, a combination of amount and GI carbs can affect how long it takes to fall asleep and how often you wake up while sleeping.

The complexity of sugars could affect your sleep because sugar can change the levels of tryptophan in your blood, according to a 2020 Mediators of Inflammation study. Tryptophan is a chemical used to make serotonin, a brain chemical that promotes sleep. After eating high-GI foods, your body produces more serotonin, helping you fall asleep. By that logic, a sweet snack before bed should lead to better sleep.

However, a 2020 article in The American Journal of Clinical Nutrition found that people who ate high-GI foods had a harder time staying asleep. The authors proposed that high-GI sugars would initially make you produce serotonin and feel sleepy. But later, because of the spike in your blood sugar, your body may overcompensate and lower your blood sugar below the normal levels. You could then produce hormones like adrenaline that wake you up.

Scientists are still debating how sugar changes your body, but they agree that sugar does affect your sleep. Eating any form of carbs before you sleep could change how you rest⁠—and disrupted sleep could lead to nightmares.

Foods That Irritate Your Body May Cause Nightmares

Eating too much of certain foods like sugar can make your body uncomfortable. The resulting discomfort at night from late-night meals could disrupt your sleep and cause nightmares. A 2018 Nutrients study found that eating foods with higher GI scores was associated with more inflammation— this shows that the study participants' bodies were irritated by the diet. That chronic (long-term) inflammation can lead to other conditions or change your gut microbiome, affecting your sleep in the future.

How Can I Snack To Avoid Nightmares?

Though researchers are debating how sugar can affect sleep and nightmares, you can try cutting out nighttime sweets and other forms of carbs. If that works to reduce your nightmares, you can keep avoiding them.

Besides reducing sugar, you can make other changes to your late-night snacks, like avoiding foods known to disrupt sleep like alcohol or caffeine. Also, avoid eating fatty or spicy foods before bed, since those can cause indigestion, leading to fitful rest and possibly nightmares.

For people with low blood sugar, also known as hypoglycemia, make sure to eat a bedtime snack to maintain your blood sugar level through the night. Some symptoms of hypoglycemia include shakiness, sweating, or confusion. If you have low blood sugar, try yogurt with granola or a graham cracker with peanut butter; both snacks contain carbs to boost your blood sugar, plus protein to keep it from crashing.

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