WATER used to fall from the sky and we drank it. Now it is so complicated you need a manual to understand it. The United States Department of Health and Human Services, under the Food and Drug Administration, produced such a manual last year. Entitled 'Beverages: Bottled Water', it ran to 102 single-spaced A4 pages. Its aim: to 'establish a standard of identity for bottled water' and to 'recodify the standard of quality'. Establishing water's identity, among other things, meant defining mineral (untreated water from a natural source containing not less than 250 milligrams per litre of minerals), artesian (pumped from an aquifer or well), spring (from a natural spring but can be treated), purified (distilled or deionised), and sparkling (with natural carbonation). Europe has similar terms, but there mineral water does not need a minimum content but must be consistent. Yet much of the water you buy is little different from what comes out of your kitchen tap - and that may be the best for you anyway. Such complications for simple water have come about because it has become big business. In the US, water sales reached US$4.3 billion (HK$33.4 billion) in 1998, according to New York consultants Beverage Marketing. Yet in Hong Kong the market is both poorly regulated and ripe for growth. Perrier has estimated that 32 litres of bottled water are drunk per person per year on average, a little more than half a litre a week, compared with the recommended three litres of water a day. And since many people do not trust tap water - which, the Water Supplies Department says, meets international standards of cleanliness and safety when it arrives at your building, but which may then sit in a tank and be pumped through unclean pipes to reach your sink - they have turned to bottled water instead. Watson's, which markets distilled water, says a survey found 82 per cent of water drinkers chose distilled. But which is better for you? The trouble is, there is no legal definition of different types of water in the SAR. Did you realise, for example, that there is a huge difference between mineral water and natural mineral water? Despite pictures of beautiful mountains and crystal clear streams on some labels, mineral water is concocted, not taken from a natural spring, as the name suggests. A Consumer Council test of 30 types of water in June last year found three locally produced 'mineral waters' were 'sourced from the local city tap and added with minerals before being processed and bottled for sales'. The three were Mountain Spring Mineral Water, 7-Eleven Mineral Water and Bonaqua. Their labels list the minerals added, but give no indication of the quantities. The Consumer Council found mineral content varied enormously, from 22 milligrams per litre of calcium in Bonaqua to 3.1mg/l in the 7-Eleven brand; 17 mg/l of magnesium in Mountain Spring to 0.03 mg/l in 7-Eleven's; and 52mg/l of sodium in the 7-Eleven brand against 0.2mg/l in Mountain Spring. Daily requirements are 500mg of sodium, about 1000 mg of calcium and 350mg of magnesium. This matters because consumers may buy the water believing in the goodness of its minerals. If you have high blood pressure you need to avoid high sodium intake. The Department of Health, however, says its concern is whether water is fit for human consumption, so it checks that dangerous minerals are below a certain level and that no harmful bacteria are present. About 270 samples are taken each year and 'the food surveillance results for bottled water for the past three years are all satisfactory', a spokesman said. But when it comes to labelling, the companies have only to give a name and list of ingredients along with a sell-by date. A 'false description' can lead to prosecution,but there is no strict definition of mineral water. Imported European or US mineral waters follow their home countries' definitions and carry much more information than do local brands. Yet the 10 'natural' products tested by the Consumer Council also showed huge variations in mineral content, from 86 mg/l of calcium in Vittel to 4.3 mg/l in Apollo and Spa Reine. So what should we be drinking? Watson's has an easy answer. Stung by an article which said that hikers were better off with mineral than distilled water, the distilled water producer published an advertisement last week - headed 'Don't drink another drop of mineral water until the facts have been made perfectly clear' - in which it said mineral water contained a negligible mineral content compared with bodily requirements, and could also contain 'impurities' from the ground. 'They are not giving all the facts,' retorted Professor Georges Halpern, a nutrition consultant and professor emeritus of the University of California at Davis, now researching Chinese medicine at the University of Hong Kong. His research shows minerals in water can play an important part in the diet. Some lactose-intolerant people - which includes many Chinese - can absorb calcium from mineral water better than from milk, according to a paper published in the American Journal Of Preventive Medicine in 1991. In it he stated that 'the potential implications of this observation for the prevention and management of age-related bone loss are important . . . and indicate a new, important source of dietary calcium for lactose-intolerant individuals'. According to published figures of calcium content and our daily requirement, drinking a litre of Vittel a day could provide a 10th of daily needs, the same as some vegetables. Other scientific reports on the same subject recommend mineral water for old people to supplement calcium intake, while Professor Halpern adds that mineral water can be 'one of the best sources of magnesium', needed in the brain and muscles, and for digestion. 'Studies have been done from the end of the last century showing that some waters do have some beneficial effects in case of some diseases,' he said, adding that French doctors often advise patients to drink mineral water to aid recovery. Not only that, but 'impurities' in the form of bacteria could be good for you, he said. 'These are useful germs which we really need [for digestion and formation of B group vitamins] and their presence [in the water] prevents formation of E coli because there's competition between the bacteria. 'This is where the danger of distilled water comes. It's true that it's pure when it's produced, but if the bottling process is not perfect then the case for proliferation of E coli is greater because [the bacteria] will not find any competition,' he said. YET some waters contain high amounts of sodium.Many people get more than their daily needs through salt in food. Professor Halpern says those with high blood pressure should avoid such waters: 'We had patients who died because they were drinking sodium-rich waters, so if you elect to drink mineral water as your standard and you are not healthy you should seek medical advice.' He recommends boiled tap water. 'My recommendation is to drink hot or boiled water. That would be the safest thing to do anywhere in the world. You are going to solve all [potential] problems and get the best fluid you can.' Susan Chung So-san, vice-chairman of the Hong Kong Dieticians' Association, agrees with Watson's that food rather than water is the more important source of minerals and mineral water does not fulfil daily needs. And, she says, 'there's no good or bad water - distilled water is good for everyone' in normal circumstances. But during exercise, no water is good enough. Distilled water does not replenish the salt lost and mineral water does not replenish enough. Sports or isotonic drinks, which contain minerals in the form of electrolytes that are absorbed easily by the body, as well as some carbohydrate in the form of sugar, are the answer for hikers or those performing exercise. 'Hikers should take sports drinks if they are hiking for a few hours. They need energy to keep them going. A lot of people doing exercise get cramps because of loss of sodium and other electrolytes. If you don't replenish the sodium lost in your sweat it will give you cramps. 'The sodium in sports drinks is of the right amount - if it's too high it draws water from the stomach,' she said. And she dismisses the new 'oxygenated' waters - through which oxygen is supposed to have been bubbled so that drinkers can, as one label says, 'taste a breath of pure oxygen'. 'I query how the oxygen would be absorbed into your bloodstream . . . it will get absorbed like any other food in the gut,' she said. Stephen Wong Heung-sang, an assistant professor studying rehydration at Chinese University's department of sports science and physical education, says many people do not realise that muscles take up to two days to recover after exercise. 'I repeatedly stress the importance of taking in carbohydrate [in sports drinks],' he said. 'They should drink a carbohydrate drink before they go to the shower room. Within 30 minutes of exercise it can help restore muscle . . . the longer you leave it the longer it takes. 'We are also talking about electrolyte replacement, which will return the muscle function.' But he stresses that only two or three isotonic drinks on the market are scientifically formulated. The correct formulation is two to six per cent carbohydrate - soft drinks contain about 20 per cent, he says - and electrolyte content of about 18 to 21 mg/l for sodium, four to six mg/l for potassium. Any others he calls 'trivial'. Watson's director and general manager Edmond Tsui Pak-yin said the ad aimed to correct the misconception that mineral water could supply daily needs. 'In regard to minerals, bottled water [of either type] has either too few or none at all, making them unable to satisfy our requirements,' he said. And all the nutritionists argue that drinking any water is far better than drinking carbonated soft drinks with high acid, sugar and caffeine content. Elisabeth Tacey is the Post's deputy features editor