Unsurprisingly, coffee is perhaps the number one worst thing to consume in the evening, as it will disrupt our sleep-wake cycle. Caffeine is a central nervous system stimulant that works by blocking adenosine receptors in the brain. When these receptors aren’t blocked, adenosine can attach to them, causing sleepiness.
Coffee is great for increasing our alertness and productivity during the day. But if we drink too much (generally accepted as more than four regular cups a day, ideally before lunchtime) then we can struggle to sleep.
In fact, one study found that “consuming caffeine six hours before bedtime reduced total sleep time by one hour.” We then wake the next day feeling tired, we reach for more and more coffee, and the cycle continues.
Coffee is high in caffeine, and effective stimulant with some health benefits. But if we drink too much, too late in the day, our brains will remain “switched on” to daytime mode and we’ll experience disturbed sleep.