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Coconut water

Being potassium-rich, coconut water supposedly enhances your ability to absorb water during prolonged exercise. If that were true, though, it would also increase your risk of overhydration. In fact, studies show it is no better or worse at hydrating than a much cheaper beverage: water.

As yet there is no scientific verdict on more recently trending hyper-hydrating waters – including watermelon water, as endorsed by singer Beyoncé, and birch sap water, as endorsed by Nordic folklore.

Beetroot juice

Rich in nitrates that can relax blood vessels and improve blood circulation, there is some scientific support to the idea beetroot juice is good for you. But drink it in moderation: its sugar content is on a par with orange and other common fruit juices (see “Good hydrations: Juice and soda“). Too much nitrate has also been tentatively linked with an increased risk of stomach cancer.

Wheatgrass smoothies

Wheatgrass contains a smorgasbord of vitamins and minerals, as well as chlorophyll, claimed by some to boost the production of red blood cells. But studies show it is unlikely to benefit you much more than munching green veg such as broccoli and spinach.

Kefir

A fermented milk drink akin to yoghurt, kefir is prized for its supposed beneficial effects on microbes in our gut. Studies in mice suggest there might be a link – although it is too early to say whether there is an effect in humans, or how big it is.

Urine

Lost in the desert, you are far from any source of fresh water and your bottle is empty. What do you do? You know the drill: unzip your pants.

And not just there, if some have their way. From acne to anaemia via obesity and various cancers, many are the ills that urine has been said to alleviate – seeing as it contains vitamins, minerals, proteins, enzymes, hormones, antibodies and amino acids your body has discarded.

“The myth that urine is perfectly sterile is just that – a myth”

For Joel Topf, a nephrologist at Oakland University in Michigan, though, that’s a clue to how useful the active ingredients really are. “The chemicals are not necessarily toxic, but they aren’t something that the body wanted to hold on to the first time,” he says. Not only that, but they are at concentrations far too low to be useful.

So, urine is disgusting and unhelpful, but harmless, right? Well, maybe not. One component of urine rarely mentioned by those who promote drinking it is phosphorus, a possible cardiac toxin. The myth that urine is perfectly sterile is just that, too – a myth. Drinking it could bring you down with all sorts of nasties.

Let’s seek advice from the real survival experts. When it comes to preserving precious bodily fluids, the US army’s 1999 survival field manual puts in its “DO NOT DRINK” category. It’s not a cultural thing that we don’t like drinking urine, says Topf – it’s evolutionary. “Urine is waste, not medicine. Stop drinking your urine.”

Vinegar

Cleopatra supposedly dissolved pearls in vinegar to make Mark Antony a love potion. Some 2000 years later, people are still banging on about vinegar’s power to cure erectile dysfunction – and .

On the cardiovascular front, they might be on to something. A small-scale study conducted in 2010 at Arizona State University showed that both diabetic and non-diabetic volunteers had after a meal of complex carbohydrates if they first had a drink of diluted vinegar. Other studies have shown similar, if small, effects.

Acetic acid – the source of vinegar’s characteristic mouth-puckering bite – is generally thought to be responsible, although no one can pinpoint how. Vinegar also contains a teeming collection of . The jury is still out on whether all this actually makes you lose weight – although one South Korean study on the effects of drinking pomegranate vinegar did show that, regardless of whether participants lost weight, body fat.

Any benefits must be set against the deleterious effects of acetic acid on tooth enamel. And would-be Mark Antonys should note: for pearls to improve your sex life, they are best served whole.

This article appeared in print under the headline “Super-fluids”