Miranda Kerr's mum Therese drinks "reverse osmosis water". But does that mean the rest of us should?

Image: Therese Kerr and her daughter Miranda (Getty).

Sunday Life‘s ‘My Day on a Plate’ section can be an enlightening read for anyone who doesn’t pay close attention to health and nutrition trends.

Last year, for instance, many Australians encountered the words ‘activated almonds’ and ‘cultured vegetables’ for the first time when chef Pete Evans detailed his daily eating habits (to much derision). Now, Therese Kerr — yep, that’s Miranda‘s mum — has introduced the nation to an equally out-there dietary item.

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The 50-year-old, who has her own skincare line called Divine, explained that she begins her day with a glass of warm lemon water, followed by a second glass of H20 at 7.20am. But this one is no ordinary, tap-variety water; Kerr opts for “a glass of reverse osmosis (alkalised, mineralised) water with magnesium powder, vitamin C powder, zinc and selenium liquid.”

Who knew you could do so many different things to a humble glass of water?

Unsurprisingly, Kerr's admission didn't go unnoticed by readers, many of whom shared their amusement on social media. Aside from the expected 'it's activated almonds all over again!' commentary, a lot of people were left with questions. Namely: what on earth is reverse osmosis water, and what's wrong with drinking the stuff from the tap...?

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In short, reverse osmosis is a filtration process, whereby water is passed through a semi-permeable membrane in order to 'purify' it and remove salts, minerals and contaminants.

Although this process is claimed to improve the taste and appearance of water, Choice explains it uses a lot of energy and can effectively waste up to 85 per cent of the water involved. There's also the question of whether it has any nutritional benefit. (Post continues after gallery.)

Michele Chevalley Hedge, qualified nutritionist and founder of My Family Wellness, says reverse osmosis water is most likely going to be unnecessary, not to mention expensive, for the average person.

"You have to ask — is there a specific health condition the person has? If so, will the cost of implementing a reverse osmosis machine and adding minerals benefit the person? And it may," she explains.

Kerr's water is also 'alkalised and mineralised'. The former involves the use of additives, like pH drops, to achieve a water pH reading between seven and nine; while mineralised water has magnesium bicarbonate added.

RELATED: What is alkalising - and do I need to do it?

While these preparation techniques seem to have a dedicated following, nutritionists — including Dr Joanna McMillan, who reviewed Kerr's diet in Sunday Life — warn there's no proven health benefits beyond what you find in a glass of tap water.

"There is certainly no evidence whatsoever that alkalised, mineralised water can do any of the things the marketers say it does, including weight loss, relieving aches pains and arthritis and boosting longevity," says Accredited Practising Dietitian Nicole Senior.

"Alkalised water is a health scam, and may actually do harm. Studies in mice have found alkalised water weakened heart muscle cells and caused heart attack."

The idea behind drinking alkalised water is to offset the 'health effects' of acid-forming foods. However, Senior explains a food's acid-forming potential is not how acid or alkali it is, but the "net acid load" created during metabolism — which in high levels can affect the body's calcium levels and bone health. The way to avoid this, she says, is eating a plant-based diet and cutting down on salt.

RELATED: "I can proudly say that my diet is now low in salt."

"Drinking alkalised water makes absolutely no difference to the acid load of the diet. Regular tap water has a neutral pH (7) — although the pH can vary a little due to higher dissolved mineral and gas content – but the acidity of the stomach renders the pH of water you drink meaningless and irrelevant," Senior explains.

Regarding mineralised water, Senior says you'll get more minerals from foods that are known to be good sources of magnesium, like wholegrain cereals and green veggies. (Post continues after video.)

Then there are the various supplements and minerals Kerr adds to her water after her preparation processes — magnesium powder, vitamin C powder, zinc and selenium liquid. Although Kerr doesn't say why she uses these additives, Michele Chevalley Hedge stresses that in general, people need to be careful when adding supplements and minerals to their water or their diet.

"While they can be very beneficial for some with an underlying health condition, they can be toxic in excess in a body that does not require them," she says.

RELATED: A foolproof way to drink more water (and love it).

All this talk of water purification and additives is enough to make anyone who drinks straight from the tap feel like giving up altogether. Of all the aspects of a healthy lifestyle — regular exercise, eating enough vegetables, cutting down on salt, reducing sugar... you know the drill — water intake should be the most achievable. You don't need a lot of time or money or dedication or skill to drink an adequate amount of H2O.

So when and why did it water get so complicated? As with just about anything, it's a case of 'each to their own', so if someone wants to drink reverse osmosis water they should go ahead. But if water is fresh and clean, surely that's good enough?

Both Michele Chevalley Hedge and Nicole Senior agree that if you're drinking water of any kind, you're doing your body good.

"Drinking water is beneficial, full stop. Some people claim they feel better drinking reverse osmosis or alkalised or mineralised water, and often it's just simply the knock-on effect of being more hydrated," Chevalley Hedge says.

"In Australia our tap water is safe and good quality. There is no reason to buy alkalised water, or any water for that matter. The environmental cost of the production, packaging, transport and refrigeration of bottled water is significant and you can reduce your eco-footprint by carrying around tap water in a sturdy re-usable bottle instead," adds Senior.

Do you do anything to your water?