[Column] What to eat for better sleep on summer nights

Summer nights often bring more tossing and turning. As our bodies prepare for deep sleep, they gradually lower in temperature -- but hot and humid tropical nights disrupt this natural process. The warmer your bedroom, the harder it is to fall asleep, and the more likely you are to wake up during the night. So, can food help you sleep?

Many people believe that eating monosodium glutamate (MSG) makes them sleepy, but this is a misconception. MSG does not cross the blood-brain barrier and therefore has no direct sleep-inducing effect. Glutamic acid is synthesized in the brain, and most dietary MSG is metabolized in the gastrointestinal tract. Decades of research since the “Chinese restaurant syndrome” controversy in the 1960s have consistently concluded that MSG is unlikely to cause drowsiness or headaches.

Salty foods can induce drowsiness. In 2016, researchers at the Scripps Research Institute in the United States observed increased postprandial sleepiness in fruit flies fed a high-protein, high-salt diet. Humans respond in similar ways. If you’ve ever woken up from a weekend nap after a meat-heavy meal with a dry mouth, it was likely due to the salty, fatty food -- not the lettuce wraps. However, intentionally eating salty foods won’t help you sleep better. A follow-up study by the same team found that fruit flies on a high-salt diet experienced poorer sleep quality. In other words, while protein and salt may make you feel sleepy, they don’t lead to the deep, restorative sleep your body needs.

So, what should you eat -- and how should you eat -- to sleep better on summer nights? First, avoid alcohol. While it may initially make you feel drowsy, the way your body metabolizes alcohol keeps your brain active and causes frequent early-morning awakenings. Alcohol is also a diuretic, meaning you’re more likely to wake up to use the bathroom. If this becomes a habit, it can lead to a vicious cycle: poor sleep leads to a morning coffee habit, which then keeps you awake at night. It’s also wise to avoid caffeinated foods and drinks -- like coffee and energy drinks -- after the afternoon, as caffeine can remain active in the brain for more than eight hours.

It’s also hard to fall asleep when you’re too hungry -- an empty stomach can trigger alertness. On the other hand, overeating can disrupt a good night’s rest. A diet high in fat and sugar, in particular, can prevent deep sleep, burden your stomach, and slow down the body’s recovery. One study found that people consume an average of 400 to 500 more calories -- and significantly more fat -- on days when they don’t sleep well.

The conclusion is clear: the best food for summer nights is a light, balanced dinner -- something not too salty, not too fatty, and rich in fiber. More than any specific ingredient, it’s the timing, quantity, and combination of foods that matter most. Sleep comes to a body that’s prepared, and that preparation begins at the dinner table on a hot summer night.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness, and medications. This column was originally published in Korean in Joongang Ilbo on July 17, 2025. – Ed.