Do recommended health targets as advised by the government work? Get 150 minutes of exercise a week, eat 5 portions of fruit and vegetables a day, drink 8 glasses of water a day etc…. You are constantly reminded of these recommendations such that they almost seem a given. But how true are these guidelines and where did they come from?
“Get 150 minutes of exercise a week”
The recommendation by the National Health Service is for UK adults to get 150 minutes of moderate or 75 minutes of vigorous exercise a week. Moderate exercise includes walking, roller-blading and lawn-mowing, whilst vigorous activity includes running, swimming or aerobics.
Based on 4 decades of research, you have a significantly less risk of dying from disease and that your risk of a heart attack is around 20 % lower if you follow these guidelines. According to Gavin Sandercock, professor of sport, rehabilitation and exercise sciences at the University of Essex, ‘the science is really strong for vigorous activity’. Anything that results in an elevated heart rate is positive for your health.
The issue with this recommendation is that it is difficult to estimate precisely how much exercise you have actually done. It is easy to work out how much you have run each week, but walking is more difficult as, unless it is planned, severything in theory counts.
Koula Asimakopolou from King’s College London states health targets in and of themselves don’t provide any form of motivation. It relies solely upon willpower and determination alone. She recommends doing activities that you enjoy. She also recommends planning your exercise activity on a regular basis. Doing it with friends as well means you will be more likely to feel motivated to do the exercise.
“Drink 8 glasses of water a day”
The recommended health target for fluid intake by the NHS is 6 to 8 glasses of fluid a day. That may also include coffee, milk and lager. The original claim came from a 1945 recommendation from the National Health Research Council in the US. It advised that for every calorie of food, 1 millimetre of water should also be consumed. This equates to around 2.5 litres for men and 2 litres for women.
However, this recommendation has no credible scientific basis. Thanks to recent ground-breaking research, the body has its own unique sensory system for estimating its fluid intake requirements. Therefore, whenever you sense an urge to drink, let that be your guide. The origins of thirst are that simple. Your urine colour may serve as a rough approximation too.
“Eat 5 portions of fruit or veg a day”
The origins of this recommended health target come from the World Health Organisation (WHO). According to the WHO, people should eat a minimum of 400 grams of fruit and veg a day. This recommendation was based on consistent research suggesting an increased risk of cancer for those diets comprising a lower intake of fruits and vegetables.
In 2017, a study performed by the team at Imperial College suggests that this amount should be doubled to 800 grams a day. The team suggested that eating more fruits and vegetables could save the lives of 7.8 million people who are at risk of dying prematurely.
Whilst these recommendations may serve as a useful guide, in practice it is difficult. Fruit juice counts as a portion yet it is laden with fructose (a form of sugar). Fruit juice when consumed in excess isn’t healthy. There is also a lack of consistency across the world as to what counts as ‘fruit and veg’. For example, in the UK, potatoes or yams are not included, yet in Australia they are.
Furthermore, it seems that particular types of vegetables are more beneficial than others. This includes cruciferous vegetables such as brussel sprouts, broccoli and cabbage, pears and apples, berries, kale and citrus fruits. In this context, it may be better to focus on eating more of a particular type of fruit and vegetable than obsessing about how much fruit and vegetables to eat on a daily basis.
Of course, from a behavioural science perspective, having an actual plan how to achieve your ‘5/10 a day’ means you will more likely to succeed. Asimakopoulou cites the SMART objective setting system an example. Planning on what, when and how you will achieve the recommended daily intake target may help achieve that daily health target.
“Brush your teeth for 2 minutes, twice a day”
The recommended time for brushing your teeth at least twice a day for 2 minutes is almost folklore. The origins however are not clear. Some studies suggest once a day is adequate.
That said, there is little doubt about the connection between oral hygiene and health. Some studies suggest that gum disease may be implicated in Alzheimers disease as well a higher risk of stroke or heart disease. Good oral hygiene removes the thin film of bacteria that form on the teeth. This acts to disrupt their colonisation and therefore harm potential.
As for 2 minutes a day, a Dutch study showed that when people brushed their teeth for 2 minutes, only 41 percent of the plaque was removed. For those who brushed for 1 minute, it was even lower – just 27 per cent. As this is quite low, perhaps brushing for an even longer period is useful.
However, even with this idea, there is no clear consensus with some researchers arguing that brushing with hard bristles for a longer period may actually damage the teeth. That said, with the average British brushing time of just 45 seconds, a longer brushing time is probably sensible.
In all, brushing your teeth for around 2 minutes a day seems adequate. Those who suffer from tooth decay or consume a lot of sugary foods in between meals may require more.
“Consume 2,000 calories a day”
The origins of the 2000 calories a day came from a survey produced by the US Food and Drug Administration (FDA). In the survey, people were asked to self-report their daily calorie intake. For women, it was anywhere between 1600 and 2200 calories a day. Men claimed more – between 2000 and 3000 calories a day. The average of 2350 was then taken, and then rounded down to 2000.
The reliability of this method is questionable since people tend to under-estimate the amount of calories consumed by 20-30%. How stable is your body weight, is probably a more reliable indicator of how many calories you need on a daily basis.
Furthermore, it is surprising to learn that not all calories are made equal. Take for example a hazelnut. It has high energy potential. However, it also requires a lot of energy to consume and breakdown. Also, some of that energy will remain unused as it will be locked inside the dietary fibre that is insoluble.
The same goes with eating highly processed foods versus unprocessed foods, even though they have the same amount of calories, fat, sugar and other macronutrients. Kevin Hall from the US Department of Health & Human Services has found that eating ultra-processed foods compared to unprocessed foods results in a greater weight gain despite their equivalent nutritional basis.
What is also interesting to note is the variation in unprocessed foods, some up to 20% due its unique biology. Apples are a good example, with different types having higher or lower levels of sugar. Even apples grown on the same tree can vary in sugar content by up to 10% according to the amount of sunshine it receives.
Overall, what it is known about nutrition, focusing on calories isn’t a useful measure of health. Rather, focusing on the nutritional benefit of the food and how you react to it is important. Knowing that a particular food causes a blood sugar spike is enough to avoid or limit consumption.
“Get 8 hours sleep a day”
The recommended health target of 7 to hours 8 sleep a day is well recognised. This appears to be the amount of time that is needed for the brain to restore itself and the rest of the body. Deep sleep flushes out metabolic waste products through the glymphatic system, including amyloid protein, which has been associated with Alzheimers disease.
Some people can live off less sleep, however 7 to 8 hours appears to be the average, according to Dr Nilong Vyas at the paediatric sleep consultancy in NOLA and a medical review expert at the Sleep Foundation.
Some studies have tried to show a link between sleep and longevity. In 1964, a study of more than 1 million Americans showed that those who got 7 hours of sleep a night experienced a decreased risk of early death, whilst 5 hours sleep a night was associated with significantly elevated rates.
Not only does the amount of sleep you get seem to affect your lifespan, but also your cognitive capacity as well. A study showed that those who got around 4 hours sleep a night had the cognition of someone who was almost 8 hours older than they were. I think you know the feeling of ‘brain fog’ at work after a poor night’s sleep.
That said, another study in 2019 found that due to genetic variation in certain DNA mutations, some people can thrive on having just 4 hours sleep a night.
Whilst 7 to 8 hours seems to be the ‘right amount of sleep’, this in and of itself is not a useful indicator of ‘sleep health’ unless it is accompanied by behavioural change that results in deep rest. There is a significant difference between having 7 to 8 hours of sleep and actually resting deeply during that sleep. The usual advice applies. Limiting screen time well before bed time, eating a lighter meal and leaving a significant gap between eating and sleeping all contribute to how well one sleeps.
“Take 10,000 steps a day”
The recommendation to take 10,000 steps a day is a pure gimmick. It has its origins from the 1964 Tokyo Olympics During such time, the world’s first commercial pedometer went on sale. It was called the ‘manpo-kei’ which translates to “10,000 steps meter”.
Although this recommended health target has no scientific basis, some research has been done on how certain tribes of people live, which provide an insight into the evolution of man-kind and the level of activity that best supports human existence. One such group is the Hadza people in Tanzania. One study showed that Hadza men aged between 18 and 75 years walked almost 20,000 steps a day, with women roughly half that. As a whole, the Hadza people enjoy a healthy and long life.
So there does seem to suggest a relationship between health and longevity, it also comes down to the quality of those steps. A step counter doesn’t really measure your steps, but rather the movement of your hands and hips. The most important thing is the amount of energy expended. One study suggests that both moderate walking and vigorous running offer similar levels of health benefits in terms of risk of high blood pressure, diabetes and levels of cholesterol.
To this extent, an important measure is the rate of energy expenditure (known as the metabolic equivalent (MET)). The slower you walk, the less energy is expended. To the contrary, walking briskly up a steep hill requires more energy. So not all steps are equal.
Given it is known that sedentary lifestyles contribute towards increased risk of mortality, then remembering that ‘10,000 steps’ was just a marketing ploy is helpful. Rather focusing on the quality of those steps taken and how much energy is consumed is a better measure of how much activity you have on a regular basis.
Recommended health targets serve a value in helping you to strive to leave a healthier lifestyle. However, for the most part, they are only recommendations. Some of them are grounded in marketing such as ‘10,000 steps’ a day and others based on rough estimates without taking into account natural variation in the quality of foods consumed (ie 2,000 calories a day).
Overall, the best advice is to listen to your body and mind and use that as a basis for living a healthy, balanced lifestyle. Your body is a pretty reliable indicator, which no app or other device will be able to replicate.
That said, health targets at least provide a signal to society that developing good habits with respect to wellbeing should be a priority. To this extent, even though science is imperfect, they still hold some value.
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Amy Fleming, ‘Recommended health targets: Do they work?’, Science Focus, Issue 386, New Year 2023.
Leader 2021, ‘Recommended daily health targets can save us from ourselves’, New Scientist, 8 September, 2021.
Amelia Tait, ‘5 fruit and veg, 8 hours sleep: Should we trust daily health targets?’, New Scientist, 8 September, 2021.