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Sugary drinks rot your teeth, and . Fizzy pop is generally assumed to be the worst. That is not because of dissolved CO₂ – it is a myth that sparkling mineral water is any worse for your teeth than the plain variety – but because of the combination of sugar and common flavourings such as phosphoric acid.

Their high sugar content means squashes and sodas deliver a huge calorie hit without filling you up: one standard can of a drink like cola provides more than the recommended daily amount of “free” or added sugar. That piles in excess energy that we store as fat. Those who regularly imbibe sugary drinks , regardless of income or ethnicity, and consuming a can of sweetened fizz or the equivalent a day . Overall, this form of liquid sustenance has little to recommend it.

Diet sodas

So, if the main problem with sugary drinks is sugar, eliminate that and you eliminate the problem, right?

Not so fast. Some studies indicate that , but others find a seemingly paradoxical association with weight gain. Mice consuming artificial sweeteners can even develop glucose intolerance, a precursor to type 2 diabetes.

It is tricky to pin down cause and effect in human studies, says , a nutrition scientist at Harvard University: people who are already overweight may be consuming diet drinks in an effort to lose weight, skewing the stats. And the animal studies have been criticised as unrealistic, with mice or rats in some experiments consuming quantities of sweeteners equivalent to us gobbling a few hundred tablets a day.

But there are plenty of reasons why low-calorie sweeteners might not always have their intended effect. One is psychology: you had a diet cola this afternoon, so you can have an ice cream this evening. Alternatively it could be that the intenseness of the artificial stuff, which can be 200 times as sweet as sugar, drives us to prefer sweet things, says Malik. Or perhaps sweeteners disrupt our gut bacteria, or our normal hormonal response to sugar intake. “As a result, the body doesn’t respond as well when real sugar is consumed,” says at Purdue University in West Lafayette, Indiana, leading to weight gain.

The latest review concluded last year that choosing diet drinks over normal sugary drinks . But the uncertainty should give us pause for thought, says Swithers. “The reality is that no one should be drinking a sweetened beverage every day, whether it’s regular soda or ‘diet’ soda,” she says. “It’s like candy in a can either way.”

Fruit juices

Pure fruit juice feels like a healthy alternative. It’s 100 per cent fruit, after all, and contains good stuff that fizzy drinks don’t, such as vitamins, minerals and antioxidants. The UK National Health Service says one small 150 millilitre glass of pure fruit juice .

But only one. Fruit juice is missing a lot that fruit has: the juice of one orange contains 0.4 grams of fibre, compared with 1.7 grams in an actual orange. And it is as sickly sweet as sweetened drinks. that the natural sugar in fruit juice should be lumped together with that added to food and sweetened drinks as free sugar, and advises strict limits on how much we should consume. Orange juice and Coca-Cola contain roughly the same amount, and some juices even more (see “Sugar to go”). That suggests pure fruit juices should carry the same health warnings as added-sugar drinks.

In truth, we don’t know whether fruit juices are better or worse for you than soda, says epidemiologist of the University of Cambridge: other lifestyle factors such as income, diet, smoking and exercise that may differ between habitual juice drinkers and habitual soda drinkers make it hard to draw watertight conclusions.

A review by Forouhi’s group and others in 2015 did conclude that added-sugar drinks, artificially sweetened drinks and fruit juices were , but differing study designs mean the evidence for artificially sweetened drinks and fruit juices might be “subject to bias”. In other words, the jury’s still out.

Sports drinks

Sports drinks’ main claim is that they improve athletic performance and recovery by replacing fluid, energy and electrolytes – sodium, potassium and chloride – lost during exercise. A review published in 2000 concluded that sports drinks with drinking water. In 2006 the European Food Safety Authority agreed.

But most sports drinks also come with a stonking sugar content, and more recent studies have . An analysis published in the BMJ in 2012 found a for any claim related to sports drinks. They may help elite athletes, but are unlikely to do anything for ordinary people.

In the meantime, there’s another competitor: low-fat chocolate milk. Its 4:1 mixture of carbohydrates and protein , and it is cheaper than most alternatives, too. “The research has been positive – most studies have found it to be just as effective or superior to an over-the-counter recovery beverage,” says nutrition and exercise scientist Kelly Pritchett of Central Washington University in Ellensburg.

This article appeared in print under the headline “Soda, squash and juice”