For example, due to their natural sources, mineral water can contain trace amounts of elements.
Some, like arsenic, can be beneficial in tiny quantities.
But others may not be good for the body.
“Some minerals, like fluoride, may also be present in quantities that are not acceptable to certain groups of people,” Dr Wuang said.
They include infants and young children, who already get fluoride that is added to tap water.
A 2012 study by the Harvard School of Public Health found that children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas.
“So, while it’s good to have natural minerals, it is also important to check the contents,” she added.
While it may be an “over-generalisation” to determine which type of water is better, Dr Wuang said that a greater awareness of each type of drinking water can potentially help “consumers make informed choices”.
Associate Professor Richard Webster from Nanyang Technological University’s School of Physical and Mathematical Sciences said that water marketed as artesian or untouched by humans is not better.
“It is just a marketing gimmick,” he said. “There is no real difference from other bottled water.”
The benefits of a new entrant – water with added oxygen – are also unproven, said Prof Webster.
“We get enough oxygen from breathing air, so adding it to water will not make any difference,” he added.
Home-grown water-treatment specialist Hyflux is working with Changi General Hospital (CGH) to see if its oxygenated Elo Water can help diabetic patients achieve better glycaemic control.
A study conducted by Harvard Medical School and Erasmus University Medical Centre in Rotterdam, the Netherlands, found that diabetic patients have 10 to 15 per cent lower tissue oxygen levels, compared with non-diabetic patients. The study was published in 2008.
It was previously reported that studies have found that Elo Water improved oxygen levels in animal and human tissue.
For the consumer, however, price appears to be the main criterion for choosing bottled water.
A FairPrice spokesman said sales for the budget range of bottled water has increased.
Similarly, in Sheng Siong, the cheapest bottled water is the most popular.
But the fact that the water is bottled can raise environmental concerns.
The website of non-profit organisation The Water Project states that these plastic bottles take more than 1,000 years to biodegrade, and they also produce toxic fumes if incinerated.
It also takes an estimated 3 litres of water to package a 1-litre bottle. And bottled water burns a bigger hole in the pocket too.
According to national water agency PUB, tap water can be 1,000 times cheaper than bottled water.
A 600ml bottle of drinking water costs between 50 cents and $1, while tap water costs 0.1 cent for the same amount.
Giving his assessment of tap water in Singapore, Dr Webster said: “It is better than what is available in many other countries.”
Family spends $200 monthly on bottled water
Pull back the sofa at the Goh family home and you will find close to 100 bottles of water stacked neatly against the wall.
Accounts executive Francis Goh and his family do not drink tap water at home. When they make drinks like tea or coffee, they run the water through a filtration system before using it.
Mr Goh, 63, spends close to $200 a month on bottled water and the family members go through at least 12 1.5-litre bottles a week.
He also buys 500ml bottles of water for his four children to take along when they go out.
The Goh family made the switch to bottled water in the early 2000s.
Daughter, Sarah, 21, an undergraduate, said her aunt in the United States had convinced them to switch due to concerns over chlorine levels in tap water.
But Mr Goh’s children do drink tap water when they are out. Son, Gabriel, 24, also an undergraduate, said: “Water is still water. The idea is to decrease the chlorine intake.”
Experts say the level of chlorine in Singapore’s tap water is within acceptable limits.
In 2016, chlorine levels in all the waterworks ranged from 2.04 to 2.98mg per litre, well within the World Health Organisation’s limits of 5mg per litre.
The Gohs believe that since making the switch, they have been falling sick less often.
The younger Mr Goh said his family is willing to spend money on bottled water for peace of mind.
Asked if they would ever give up drinking bottled water, he said: “If it gets too expensive, yes, of course.”
Until then, they are happy to continue drinking bottled water. They buy Evian and Vittel mineral water in 1.5-litre bottles and Ice Mountain in 500ml bottles.
“We like the taste of Evian more. The small bottles are expensive,” said Mr Goh.
Correction note: In our earlier story, we said that a study conducted by Harvard Medical School and Erasmus University Medical Centre found that diabetic patients have 10 to 50 per cent lower tissue oxygen levels, compared with non-diabetic patients. This is incorrect. Diabetic patients have 10 to 15 per cent lower tissue oxygen levels, compared with non-diabetic patients. We are sorry for the error.
Bottled water in supermarkets
When it comes down to the molecular level, all water is the same – H2O. The only difference is the presence or absence of minerals.Associate Professor Richard Webster from Nanyang Technological University’s School of Physical and Mathematical Sciences said that tap water and bottled water should be of “very similar quality” after being treated. But there are differences in terms of where the water is sourced from and how it is subsequently treated.
The following types of bottled water are available in supermarkets:
Natural mineral water is extracted from underground sources and may contain small amounts of minerals.
Sometimes, minerals may be added to water and this is also considered as mineral water.
The water is treated through the process of distillation. This involves boiling the water and re-condensing it by cooling.
Water with pH levels above 7 are alkaline. Some studies have suggested that alkaline water can help with acid reflux, high blood pressure and diabetes. Bottled alkaline water from supermarkets carries claims of pH levels of 8 and above.
This category is a catch-all for water that is considered fit to be bottled for drinking. This includes water processed by reverse osmosis.
WHAT SCIENCE SAYS
Purer, more balanced or providing health benefits – these are some claims that brands make.A report commissioned in 2001 by World Wildlife Fund International said bottled water may not be safer than tap water, as there are fewer standards to conform to. However, this has been disputed by the International Bottled Water Association.
Water with minerals was found to lower the blood pressure of people with low urinary excretion of magnesium or calcium, according to a study published in the BMC Public Health journal in 2004.
Others may also benefit, as a Montana State University professor and his team found. The study, conducted in 2010, found that people who drank mineral-based, alkaline water were better hydrated.
An in-vitro laboratory study published in Sage Journals in 2012 suggested that alkaline water could be good for patients with a reflux condition. Despite some studies affirming the benefits, experts told The Straits Times that more conclusive results are necessary to support claims for alkaline water and oxygenated water.
The British Journal Of Sports Medicine investigated claims in 2006 that athletes could gain a competitive edge by drinking water with extra oxygen, but found that the claims failed the study’s analysis and physiological tests.
When it comes to the taste of water, most people cannot tell the difference, The Guardian reported in 2011. Two earlier studies – in France and Northern Ireland – led to the conclusion that water simply tastes like, well, water.
Generally, one should drink around eight glasses of water a day, with each glass holding 250ml of water.Fluids can also be obtained from food and other beverages. The Health Promotion Board recommends choosing water over sugar- sweetened drinks, which can lead to obesity and weight gain.