Getting your five-a-day? Don’t get too comfortable – there is now a host of recommended daily and weekly prescriptions to follow for better health, covering everything from sleep to sunshine. The latest came from researchers at Cambridge University, who studied the effects of work on mental health and life satisfaction, and concluded eight hours of work a week is the key to well-being. That followed a finding from the University of Exeter, based on interviews with 20,000 people, that we should all be aiming for a two-hour ‘dose’ of nature every week.

Psychologist Linda Blair says the new trend for quantitative guidelines stems from a need for simple rules to govern our increasingly hectic lifestyles – along with the arrival of technology that allows us to log and count every detail of our day.

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‘We are so busy, and we want to be looked after – we want quick answers,’ she says. ‘But the key to well-being is listening in, rather than measuring out. No two days will be alike, and rather than measuring and comparing ourselves to external standards, it’s better to listen to yourself and respond to your needs.’

Snappy as they sound, the effect of these guidelines on our behaviour is also unclear. ‘In principle, it’s a good idea to make clear what a healthy diet is, but the five-a-day message, for example, hasn’t produced any marked change in consumption of fruit and vegetables,’ says Jack Winkler, emeritus professor of nutrition policy at London Metropolitan University. ‘Those who are interested in nutritional advice, and absorb it, are in the minority.’

So how accurate, or realistic, are the formulas thrown our way, and are they really making us any healthier?

8 hours of sleep

Sleep is now a national obsession, with apps, trackers and gurus telling us we need eight hours a night, but don’t fret if you get or need more or less. ‘We’ve no idea where that figure came from,’ says Neil Stanley, a sleep expert and author of How to Sleep Well. ‘There isn’t a shred of proof we need it.’ One possible explanation is the eight-hour day movement, which started in Australia, Britain and America in 1850, and was based around the idea that the working man needed eight hours of work, eight hours of leisure and eight hours of sleep within a 24-hour period.

‘It’s not a bad figure to aim for, but sleep is like height,’ says Stanley. ‘It’s genetically determined and we’re all different. There are short sleepers, who feel fine after four hours, and long sleepers, who need nine, so sleep trackers are quite pointless because they’re measuring something that’s as individual as a fingerprint.’

Last month, neurologist and sleep disorder specialist Dr Guy Leschziner warned sleep-tracking apps were making people so anxious about getting enough sleep, they were developing insomnia.

It’s simple to work out how many hours you need, says Stanley. ‘How do you feel at 11am each day? If you feel OK, then you’re getting enough sleep. If you feel like you could put your head down on your desk and fall asleep right there, you’re not getting enough. So ignore the eight-hour rule. It doesn’t matter how long it takes to fall asleep, how many times you wake in the night, or how you feel when you wake up. What matters is how you feel at 11am.’

10,000 steps

The 10,000-steps- a-day figure originates from a Japanese marketing campaign from the Sixties, seeking to capitalise on the 1964 Tokyo Olympics with one of the world’s first fitness trackers.

But last year Public Health England chiefs denounced the 10,000 figure, and a recent study from Harvard University found taking as few as 4,400 steps a day led to a 41 per cent reduction in mortality. Common advice is that adults aged 19 to 64 should try to get 150 minutes of moderate activity, or 75 minutes of vigorous activity, every week.

‘The 10k figure is arbitrary,’ says personal trainer Matt Roberts. ‘It isn’t based on scientific research, and it doesn’t take into account intensity. You can have somebody who shuffles around all day and hits the target, versus somebody who regularly does short bursts of intense workouts that don’t clock up many steps. With exercise, quantity isn’t everything.

‘The number I tell my clients to aim for is four: this is the number of days each week you should be exercising to the point you feel out of breath and sweaty. A jog, a brisk walk that leaves you red-faced, a bike ride or an HIIT class will suffice. Of course, clocking up 10,000 or more steps a day is no bad thing. But what should concern you is when you last built up a sweat.’

Last year, the World Health Organisation reported that the UAE ranked alongside the UK and the US as having some of the most inactive populations in the world.

5 portions of fruit and veg

This now ubiquitous formula has been embraced by the food industry, with labels helping you to count and reach your five-a-day. ‘It’s from the World Health Organisation,’ says dietitian Helen Bond, ‘which recommends 400g of fruit and vegetables each day for well-being, after several major studies found this helps in major disease prevention, including heart disease and certain cancers. It’s the minimum we should be eating, not the upper limit to aim for.’ Indeed, research published in 2017 by Imperial College London found that eating 800g of fruit and veg – 10 portions a day – cut the risk of heart disease by a quarter and cancer by 13 per cent. Unfortunately, though, most of us don’t even manage five: just 8 per cent of teenagers get their five-a-day, while 31 per cent of adults aged 19 to 54 do, and 26 per cent of over-65s.

8 glasses of water

‘The Government says we need six to eight glasses of water each day (around 1.9 litres) to stay healthy,’ says Bond. ‘But how much we really need varies on our age, gender, the weather, and how active we are.’

There is currently no unsafe upper limit for water, although excessive amounts can cause water intoxication.

‘Forget eight glasses, urine colour and thirst are the only indicators to think about,’ says Bond. ‘If you’re drinking enough water, your urine will be the colour of pale straw. If it’s darker, drink more. If you’re thirsty, drink more. And all fluid counts, apart from alcohol. Even things like coffee, tea and juice, although plain water is healthiest.’

The Daily Telegraph