PROFESSOR ROB GALLOWAY: Why I won’t be switching my kids from ‘unhealthy’ fruit juice to low-sugar pop

As a father of four — soon to be five — I worry about what I am feeding my children; I know how vital it is to give them their five-a-day, and also to limit how much processed food they eat.

And as a relatively older dad, I also worry about my diet, knowing I need to stay healthy to be there for my kids as they get older. I am aware that the same healthy-eating rules apply to me.

But every month there’s another news story that confuses me further about what we should and should not be doing when it comes to feeding ourselves and our children.

Fruit juice can count as one of your five-a-day, according to the NHS.

Yet a few weeks ago a study by researchers in Canada hit the headlines, with reports in the papers and TV news suggesting that drinking fresh fruit juice could be worse for you than drinking diet fizzy drinks.

Confused? In fact, in the sober light of day, when we look behind the headlines, I don’t think you need to ditch the fresh orange juice for a 12-pack of Diet Coke — I certainly won’t be switching my teenagers’ juice for a can of diet fizzy pop.

Not least because the news reports deemed fizzy pop ‘healthier’ because it’s lower in sugar — and that’s because it contains artificial sweeteners, which are worse in my mind (but more on that later).

The paper was written by scientists from the Department of Nutritional Sciences at the University of Toronto, who reviewed two types of research — 23 cohort studies and 19 randomised controlled trials in both adults and children.

Cohort studies are a type of observational study where researchers look at people’s behaviour — such as how much fruit juice they are drinking — and find out what has happened to them.

In the studies with children, the scientists looked at what happened to their body mass index (BMI); and for those over 18, what happened to their weight.

One of the problems with these types of studies is you cannot be sure the variable you have observed (e.g. the fruit juice) is the cause of the outcome you are interested in (e.g. the weight gain).

These studies are therefore often thought to be inferior to randomised controlled trials, which involve randomly assigning one group of people to an intervention, such as drinking fruit juice, and comparing them with those who were not drinking fruit juice.

So what did these studies show and what do they tell us about staying healthy?

The results from the cohort studies in children — involving more than 45,000 participants, over time periods of between eight months to ten years — revealed that, overall, the children’s BMI increased by 0.03 for every 250ml of fruit juice consumed per day.

But are these results actually significant? If the results had shown a BMI increase of 3 — rather than 0.03 — then this would be of concern.

But a 0.03 increase in BMI is a matter of 50 to 100g or so of additional weight.

The scientists then did something called a ‘subgroup analysis’ — splitting the children into those aged under 11 and those older than this.

This showed that in the over-11 age group, rather than their BMI rising, it actually fell by 0.001 for every extra 250ml of fruit juice consumed a day (though, again, this is insignificant).

However, if you were younger, your BMI went up by 0.15 for every 250ml of fruit juice you had.

Based on the observations of my children and what happens to the fruit juice in the fridge if I’m not closely monitoring them, children can drink up to a litre a day.

This would mean that their BMI could go up by 0.6, and they’d be 1kg to 3kg heavier. But that doesn’t mean juice is unhealthy and that fizzy pop is fine.

And what the researchers didn’t do was look at the impact on the children of drinking artificially sweetened drinks.

When it comes to the adults, the cohort studies showed that those who drank more than 250ml of fruit juice a day weighed 0.2kg more than the non-fruit juice drinkers, which they were able to show was because of the extra calories in the fruit juice.

But, fascinatingly, the randomised controlled studies showed that when people had just 250ml of fruit juice a day, it led to weight loss.

And even more fascinating was the fact that fruit juices such as apple, orange and grape led to weight gain — while so-called ‘superfood’ juices, such as pomegranate, led to weight loss.

So why did these studies show a glass of juice led to weight loss despite those additional calories?

In many of the trials, the non-fruit juice drinkers were given alternative low-sugar (i.e. diet) drinks containing artificial sweeteners. We used to think these were harmless — but recent data shows how wrong we were.

Although individual studies have shown conflicting results, a 2017 analysis of studies in the Canadian Medical Association Journal showed that rather than helping us lose weight, diet drinks actually led to weight gain.

How can that happen when the amount of calories drunk is being reduced? The answer was found in studies on rats, which showed that the part of the brain involved in controlling how much you eat was damaged by the intake of artificial sweeteners and thus more calories were consumed overall.

But it’s not just the sweeteners. Many diet drinks are carbonated, and a study in Obesity Research & Clinical Practice in 2017 showed that drinking carbonated drinks led to higher levels of ghrelin, the hunger hormone.

This may explain why a reduction in the amount of sugar in drinks is not having the expected impact on obesity.

In 2018 a sugar tax was introduced, which led to many drinks being reformulated with less sugar and more sweeteners, as well as causing more people to drink diet versions of their favourite drinks. More than 45,000 tons of sugar has since been removed from soft drinks in the UK.

Yet obesity rates are still rising — possibly because the sweeteners and diet versions of drinks are pushing people to consume more calories overall.

The bottom line is this: the new Canadian study shows that small amounts of fruit juice are completely safe and have very little impact on weight for those aged over 11. However, in under-11s it can cause some weight gain if they drink more than one glass a day.

The fact is, in small amounts, juice is beneficial, as it contains vital vitamins and nutrients — the NHS says 150ml of juice can count as one of your five-a-day.

But as the fibre of fruit is pulverised when you juice it, too much juice can spike your blood sugar levels, and if you drink more than a glass a day the benefits of the vitamins and nutrients is undone by the negatives of the sugar rush (including weight gain).

There’s another reason to be cautious, with children at least: introducing sweet tastes at a younger age encourages them to want more sugary foods as they get older, so I would consider trying to limit fruit juices in those under 11.

But obviously don’t replace them with full-sugar carbonated drinks or, the next worst thing, diet carbonated drinks, or drinks full of artificial sweeteners, in the belief that ‘lower in sugar’ is better.

These drinks, too, can cause weight gain in their own right and are not a healthy alternative.

At home I’ve now replaced the copious amounts of fruit juice and diet drinks that I used to have (thinking it would be healthy) and now drink water and eat fruit.

On occasion, I drink a glass of fruit juice, too.

I believe it has helped me to lose a few kilos — and the scientific evidence backs me up!