It's best to brush your teeth before breakfast, says dentist Dr Shaadi Manouchehri.
From drinking coffee to asking for a pay rise, researchers claim there is an optimal window of opportunity to do most things. Here’s what they advise.
7.22am
We’ve all heard of entrepreneurs and fitness fanatics who wake at dawn to work out or hit their desks. Should you do the same? Maybe not. A study by the University of Westminster found that people who woke between 5.22am and 7.21am had higher levels of the stress hormone cortisol than those who slept later. They were also more likely to suffer from muscle aches, colds and headaches, and had worse moods.
This may be because they miss out on sleep, or because they are working against their chronotype – the genetically programmed tendency to be either a late-to-bed owl or an early-rising lark.
Dr Neil Stanley, an independent sleep expert and the author of How to Sleep Well, says that while a 7am wake time is likely to be practical for most people, “a recent study shows that the most important thing for longevity, even more than duration of sleep, is consistency of wake time.” This means, he says, that we should try to wake up at the same time, “plus or minus one hour”, every day, even at weekends.
Before breakfast
You might habitually reach for your toothbrush to scrub away toast crumbs and ensure a clean start to the day. But, says dentist Dr Shaadi Manouchehri, you could also be scouring away your precious dental enamel. She says that when we eat, the natural bacteria in our mouths produce acid to break down the sugar in food.
“So, if you brush your teeth, you are rubbing that acid on the tooth which is a mineral and it can wear it down,” she says.
If you hate the idea of heading out without sparkling gnashers, either eat earlier so you can wait until an hour after eating before brushing, or brush your teeth before eating.
Before 8am
Last year, a study of more than 100,000 people found that eating breakfast after 9am increases the risk of developing type 2 diabetes by 59 per cent compared to people who eat breakfast before 8am.
“We know that meal timing plays a key role in regulating circadian rhythms and glucose and lipid control,” said Anna Palomar Cros, a researcher at the Barcelona Institute for Global Health.
“Our results suggest that a first meal before 8am and a last meal before 7pm may help reduce the incidence of type 2 diabetes,” added Manolis Kogevinas, co-author of the study.
Another study showed that 9am breakfasters are 6 per cent more likely to develop cardiovascular disease than those who eat at 8am. They are also more likely to have healthy blood pressure and cholesterol levels. Dr Stanley says eating breakfast is “a sign to your body it is daytime and is important for regulating your biological clock”.
Between 11am and 12pm
Professor Russell Foster, a University of Oxford neuroscientist, is the author of Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health. “Our cognitive ability and reaction time peaks between 11am and noon,” he says, “and our mood is also highest at this time, which means it’s a good time to ask for a favour or a pay rise.”
Daniel Pink, the author of When: The Scientific Secrets of Perfect Timing, says that mood and alertness fall during the sluggish post-lunch dip from 1pm to 4pm. And never fire off an important email in the small hours. “Our cognition at 5am is worse than if we were drunk,” says Pink.
Between midday and 4pm
Last year, a UK study found that regular naps can help preserve reaction time and memory as we age – as well as leaving us feeling refreshed and more alert.
According to the Sleep Foundation, if your lifestyle allows, naps should be between 10 and 20 minutes long, and end before 2pm to avoid interfering with night-time sleep. A Japanese study showed that a 20-minute nap at 12.20pm could wipe out the typical afternoon drop in energy. A cup of coffee before your nap can help you wake up naturally, as caffeine takes about 30 minutes to affect your system.
Morning for sleep and weight loss, afternoon for muscle gain
A recent US study found that, for women, morning workouts between 6:30am and 8:30am reduced abdominal fat and lowered blood pressure. But evening workouts between 6pm and 8pm best enhanced endurance and built muscle.
For men, evening workouts were the most effective to burn fat and reduce blood pressure. Generally, studies have shown that scheduling morning exercise could help you stick to healthy exercise habits, shift your body clock to function earlier in the day, encourage more movement and enhance weight loss better than evening workouts.
Some research suggests that, compared to exercising at 7pm, a 7am run or other aerobic exercise may be key to better sleep and lower blood pressure. However, Dr Stanley says: “You can exercise when you like without it affecting your sleep as long as you allow your body temperature and heart rate to return to normal before you go to bed, so have a cool-down stretch, maybe a shower, and ease into your bedtime routine.”
One study suggests that, over time, evening exercise can reduce levels of the “hunger hormone” ghrelin.
After 9am and before 2pm
Caffeine blocks brain receptors that detect adenosine, a neurotransmitter in the body that builds up during the day and makes us feel sleepy. However, in the morning adenosine levels are low and the alerting hormone cortisol is high, so coffee might not give you the lift you expect. If you want to sleep well, avoid coffee after 2pm, as it can take eight hours or more to be fully metabolised.
However, Dr Stanley says: “Some people are more sensitive to caffeine than others, so if you sleep perfectly well after a late-night espresso, keep drinking it. If you know you won’t sleep well, skip it.”
7pm to 8pm
Eating late – around 10pm – can increase the risk of weight gain and diabetes. Scientists in Spain found that people who ate dinner within two hours of bedtime were five times more likely to be obese than early diners. Professor Foster says: “We are programmed to deal with calories and sugar much better during the first half of the day than the second. If you eat late, you are more likely to lay down calories as stored fat and to store glucose in the liver. It’s best to eat a large breakfast and lunch and a small evening meal.”
Dr Stanley says: “We need to lose one degree of body temperature to fall asleep. Burning calories creates heat, so a late large meal will warm you up when you should be cooling down. Ideally you should eat no later than three hours before bedtime.”
However, you also don’t want to go to bed hungry, as this can prevent you from dropping off. “A small bedtime snack is fine,” Stanley says.
10pm to 11pm
According to research published in the European Heart Journal, a bedtime between 10pm and 11pm may cut your risk of heart and circulatory disease compared to people who hit the hay later. People who fall asleep after midnight have a 25 per cent higher risk of heart attack and stroke compared to early sleepers.
Ideally, we should sleep between six and eight hours a night on average, although, says Professor Foster, “some people may need as much as 10″.
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