I don’t drink a lot. It’s not because I don’t appreciate a glass of wine with a great meal, or a few beers on a hot summer evening. It’s because I know what alcohol can do to sleep and healthy circadian rhythms.
Alcohol is the most common sleep aid—at least 20 percent of American adults rely on it for help falling asleep. But the truth is, drinking regularly—even moderate drinking—is much more likely to interfere with your sleep than to assist it.
Does this mean you need to abstain from drinking altogether? Nope. But part of a smart, sleep-friendly lifestyle is managing alcohol consumption so it doesn’t disrupt your sleep and circadian rhythms.
How alcohol affects circadian rhythms—and why it matters to your health
First, a quick refresher on the importance of the body’s circadian rhythms. These 24-hour rhythms are governed by a master biological clock, a tiny region of the brain with a big job: to coordinate circadian rhythm activity throughout the body.
Circadian rhythms regulate nearly all of the body’s processes, from metabolism and immunity to energy, sleep, and sexual drive, cognitive functions and mood.
In the body, alcohol disrupts circadian functioning, directly interfering with the ability of the master biological clock to synchronize itself. Because circadian rhythms have such a powerful, dominating influence over the way our bodies function, the disruptive effects of alcohol can be widespread, affecting sleep and other systems, including:
Poor liver function. The liver acts as a filtering system for the body, helping metabolize food and chemicals (including alcohol itself), and pulling toxins from the bloodstream. Like nearly all of the body’s organs, the liver functions according to circadian rhythms. Alcohol interferes with these circadian rhythms regulating the liver, and can contribute to compromised liver function, liver toxicity, and disease.
Leaky gut. The gut and its microbiome are often referred to as the body’s second brain, and operate under powerful circadian rhythm activity. The circadian disruption that can result from alcohol consumption contributes to leaky gut syndrome, according to research. Circadian rhythms thrown out of sync can weaken the lining of the gastrointestinal tract, making it more vulnerable to permeation—that’s the leakiness that allows bacteria, toxins, and food to leave the intestines and enter the bloodstream.
Depression. There’s a complicated relationship among depression, alcohol, and sleep. People suffering from depression may already have disrupted circadian rhythms, and the presence of even moderate amounts of alcohol may push those rhythms further out of sync.
Disrupted sleep-wake cycles. Alcohol is highly effective at suppressing melatonin, a key facilitator of sleep and regulator of sleep-wake cycles. Research indicates that a moderate dose of alcohol up to an hour before bedtime can reduce melatonin production by nearly 20 percent. Alcohol has a direct effect on circadian rhythms, diminishing the ability of the master biological clock to respond to the light cues that keep it in sync. Those effects of alcohol on the biological clock appear to persist even without additional drinking, according to research.
There’s also evidence alcohol interferes with the body’s other sleep-wake regulator: its internal sleep drive. Alcohol elevates levels of adenosine, a chemical that regulates sleep by rising naturally in the body the longer you’ve been awake, and increasingly blocking other chemicals that stimulate wakefulness. Alcohol’s adenosine-boosting effects make you sleep at times other than you would be naturally, and can throw your natural sleep-wake cycle off course.
Circadian rhythms affect how the body responds to alcohol, depending on the timing of alcohol intake. Long-established research shows the body metabolizes alcohol differently at different times of day. Studies have shown the body is more effective at processing alcohol at certain times of the day than others.
The most effective time of day for the body to metabolize alcohol, according to research? Early to middle evening hours. That’s right, the traditional “happy hour” time is actually when the body is most prepared to process that cocktail. The time of day when the body is least well prepared? Morning. If that mimosa with brunch hits you particularly hard, it may be the result of circadian timing.
How alcohol affects sleep
Before we look at the effects of alcohol on sleep in detail, here’s the basic bottom line. The more you drink, and the closer your drinking is to bedtime, the more it will negatively impact your sleep. Even moderate amounts of alcohol in your system at bedtime alters sleep architecture—the natural flow of sleep through different stages. It also leads to lighter, more restless sleep as the night wears on, diminished sleep quality, and next-day fatigue.