Q: I read an article that says that taking 1.5 litres of water with a squeezed lemon on an empty stomach is good for health & helps in controlling pigmentation. Is this true? Can I add a pinch of sugar or salt to it?

A:An absolute minimum water requirement for humans, independent of lifestyle and culture, can be defined only for maintaining human survival. To maintain the water balance in a living human, the amount of water lost through normal activities must be regularly restored. While the amount of water required to maintain survival depends on surrounding environmental conditions and personal physiological characteristics, the overall variability of needs is quite small. Routes for water loss include evaporation from the skin, excretion losses, and insensible loss from the respiratory tract. Humans may feel thirst after a fluid loss of only 1 per cent of bodily fluid and be in danger of death when fluid loss nears 10 per cent Prior physiological studies have generated reference values for a daily human water requirement. Minimum water requirements for fluid replacement have been estimated at about three litres per day under average temperate climate conditions. When climate and levels of activity are changed, these daily minimum water requirements can increase. In a hot climate, a 70-kilogram human will sweat between four and six titers per day without a. comparable change in food intake or activity The National Research Council of the National Academy of Sciences in the U.S.A. separately estimated minimum human water requirements by correlating them with energy intake in food. They recommend a minimum water intake of between one and one-and-a-half millilitres of water per calorie of food (1 - 1.5 ml/kcal). With recommended daily diets ranging from 2,000 to 3,000 kcal, minimum water requirements are between 2,000 and 4,500 millilitres, or 2 to 4.5 litres per day. Using these data, a minimum water requirement for human survival under typical temperate climates with normal activity can be set at three litres per day. Given that substantial populations live in tropical and subtropical climates, it is necessary to increase this minimum slightly, to about five l/p/d. A further fundamental requirement not usually noted in the physiological literature is that this water should be of sufficient quality to prevent water-related diseases. The consumption of water on an empty stomach is advocated in alternative medicine and we are not qualified to comment on it.