Tap water may be better than the bottled variety

It's important to drink about two litres of water every day, but what's the best source - filtered from the tap or bottled? Nadine Bateman asks the experts
Humans can survive for quite a long time without food but it doesn't take long to suffer from dehydration. We lose water through sweat, urine, faeces and even just breathing. In severe heat a human can lose up to 1.5 litres of water an hour.
Our bodies are mostly comprised of water - it's in every cell, tissue and organ, it keeps our body temperature normal, lubricates and cushions our joints, protects our spinal cord and other sensitive tissues, and eliminates waste through urination, perspiration and bowel movements.
Dr Sue Jamieson, a GP in Central, says: "Depending on your age, 60 per cent to 80 per cent of your body is water. Your brain is about 10 per cent more water than your body," she says.
"On a basic level, water is the 'soup' in which everything survives, and it also conducts really well. We've got to transmit [our body's] signals through bio-electric means, and water's a good medium for that. So I believe it is important to drink good quality water."
The definition of good quality drinking water is highly debatable, and there are myriad options. Filtered or bottled? There are so many varieties of both. On a recent trip to the supermarket, I counted nine brands of bottled water.
Then there were the various types: spring, mineral, mineralised, distilled, for example. When it comes to filters, you can buy equipment that ranges from a simple tap fitting to elaborate and expensive units that take up a lot of kitchen space.
In the US, where the Food and Drug Administration regulates bottled water as a food, spring water is defined as that which is derived from an underground formation from which water flows naturally to the surface of the earth.
Mineralised water must contain not less than 250 parts per million total dissolved solids that originate from a geologically and physically protected underground water source, while purified water is produced by distillation, deionisation, reverse osmosis or other "suitable" processes and may also be known as demineralised, de-ionised or distilled water.
While these processes mean that harmful bacteria and impurities have been eliminated, it also means that the minerals have been eliminated, too. That's not healthy, according to experts.
Hong Kong tap water is safe ... any pathogens come from the plumbing system
Tracey Pui, Tetra
Hong Kong-based nutritionist Miles Price says we need mineral-rich drinking water because minerals are the most bio-available when they're in water - our bodies absorb them more easily.
"We need minerals because, even in daily routines such as working on computers, we lose a bit of sodium, magnesium and potassium. That always needs to be replenished through mineral-rich water or food," Price says.
"But some food, such as nuts if they're not prepared well, can block the absorption of minerals.
"The best source of water comes from a mountain stream which has been fed from a cloud in the Swiss Alps and has absorbed the minerals from the rocks."
He says that companies, such as Evian, bottle those waters and deliver them around the world so that "we can have very good quality mineral water which is pure, and not contaminated by heavy metals or environmental materials that are added during the bottling process".
Brands such as Bonaqua and Watson's which come from local water and not from a spring, have minerals added. "It's okay, you're still getting the minerals, but the water's Ph [a measurement of how acidic or alkaline a solution is] is more acidic, and that affects the metabolism," says Price.
"So the body's ability to make energy from a cellular point of view becomes less efficient, and you become more fatigued. That means the body will start drawing various minerals, such as calcium and magnesium, from the bone tissue to buffer against the acidity in the tissues.
This could lead to osteopenia or osteoporosis. "Magnesium deficiency is rampant today, so we need to make sure we optimise our calcium and magnesium 'storage'," he adds.
The problem with relying on bottled water to provide a balance of minerals is a lack of consistency between brands, says US-trained dietitian Tracey Pui, who works for the Tetra Nutritional Consultation Centre in Central.
Some brands have a high calcium content, others have nothing; some have sodium while others do not, and manufacturers in many countries, including those in Hong Kong, are not legally required to label the amount, she says.
"We have to label sodium but not calcium, potassium or magnesium," she notes. The implications of this are very important when you take into account people who may have renal disease and who need to be careful about their intake of those minerals, she says.
Pui advocates drinking municipal (tap) water. "I believe Hong Kong tap water is safe to drink. If there are any pathogens in it, then they come from the plumbing system, or the water tank in the building, so it's important for those to be kept clean and maintained."
Filters are an option, "But some only filter chlorine rather than bacteria, and the carbon filters don't work if they are not renewed on time. The reverse osmosis system can filter pathogens as well as other toxic contaminants such as mercury and cyanide," Pui says.
"The kind of filter you choose is important, as is how regularly you change it. Otherwise the filter becomes a good home for bacteria."
Pui also raises a concern about the cost of bottled water. "When [people] buy bottled water they're paying for the bottle rather than the water. "For every Hong Kong dollar you pay for bottled water, around 99 cents is for the bottle [and the manufacturing process] rather than the water. I'd say, eat a balanced diet and drink tap water. Don't buy bottled water, save your money instead."
But Hong Kong tap water also has added fluoride, which is cause for concern among some medical professionals such as Central-based family doctor Lauren Bramley. She believes fluoride is not good for us because it affects thyroid function.
Studies from China, India, and Russia that have found alterations in thyroid hormones in people exposed to elevated levels of fluoride in water.
Bramley advises using "a very good quality" filtration system, and wouldn't advocate drinking bottled water either, but for different reasons: she is concerned about the plastic leaching chemicals and other compounds into the water.
Bramley cites many studies such as recent research from the Johann Wolfgang Goethe University in Frankfurt, Germany, which uncovered what they describe as "widespread contamination" of mineral waters with endocrine disrupting chemicals that appear to have leached from packaging material.
"At my home, and in my clinic, I use a reverse osmosis [filtration] system by Life Solutions which I believe is the best one available in Hong Kong," says Bramley.
Jamieson also has concerns about chemical compounds, saying: "They are definitely something to consider, and may be another reason not to take 100 per cent of your water from plastic bottles. I drink a combination [of bottled and filtered water]."
Trying to work out what water is healthiest is a minefield, Jamieson concedes. "It's like all these faddy diets ... why not just have a mixture of things, and everything in moderation?"
The most important thing is to encourage people to drink more water, she says. "Drinking enough is so important: you need around 1½ to two litres a day, and it's better to drink constantly throughout the day, not in half-litre gulps when you suddenly remember. I think many of us have been guilty of that."