By Dr Joanna McMillan
There has long been an association between nutrition and a good night’s sleep. Many of us can remember being given a cup of warm milk by our parents when we struggled to sleep as children, and while we might dismiss this as an old wives tale, there is actually a strong connection between what we put in our mouths and the quality of our sleep.
Nutrition and sleep are surprisingly intertwined. Not only do our dietary choices affect sleep duration, sleep duration also affects our dietary choices. Insufficient sleep alters our hormone levels so that we not only eat more, but also have an increased preference for high fat, high sugar foods. It’s no surprise then that chronic sleep deprivation has been linked to obesity, type 2 diabetes and heart disease, as well as many other serious health conditions.
But while we all know we should be getting 7-8 hours every night, unfortunately it’s not always that easy. Sometimes we do all the right things; get top bed early, close the blinds and turn off our phones, but sleep just doesn’t happen. Or we’re out like a light as soon as our head hits the pillow, only to wake up a few hours later and watch the clock, becoming more frustrated with every passing sleepless minute. If you’re putting in the hours in bed but still struggle to get a good night’s sleep, it might be time to consider the role your diet could be playing.
Feeling overfull and bloated when you hit the sheets is not a good place to start when you want a restful night’s sleep. If you tend to overeat at night, try eating a little more during the day so you’re not so hungry when dinnertime rolls around. Then concentrate on eating slowly without distractions and aim to stop when you’re 80% full (the Japanese call this ‘hara hachi bu’).
Avoid eating just before bed
Digestion continues to occur long after we finish eating. So having a large meal just before you head off to bed may result in being kept awake by the busy workings of your digestive system. Going to bed straight after eating can also lead to heartburn, the ultimate nemesis of sleep.
Don’t go to bed starving. Just as going to bed overly full can prevent sleep, so can hunger. While it’s fine to go to bed a little hungry, being too hungry may keep you awake. Make sure your dinner is substantial enough to set you up for a good night’s sleep. If you’re ravenously hungry nearer bedtime have a small supper snack, but take care not to overdo it. Half a banana and a handful of nuts or glass of milk is all you need.
The truth behind the ‘glass of warm milk at bedtime’
Turns out our parents were actually onto something here. The protein in milk contains an amino acid called tryptophan, which the body uses to make the neurotransmitter serotonin and the hormone melatonin, which are both vital components of a good night’s sleep.
It’s often touted that turkey is the best source of tryptophan, however it’s no higher than other meats and the truth is that when accompanied by a whole load of other amino acids present in these foods, it doesn’t result in a greater uptake into the brain.
However with milk the combination of carbohydrates alongside the amino acids may be key. The insulin response to the carbs present actually signals the uptake of the other amino acids into muscle and other cells around the body, leaving more tryptophan in the bloodstream and in turn allowing for greater uptake to the brain.
Even in the absence of all this science it may well be that the psychological effect from warm milk may be the most important factor. The association built from childhood or simply from the belief that warm milk aids sleep, can be enough for it to actually work.