The summer is upon us and with it comes the need to make up for the loss of water and salt we face every time we "come out in the midday sun" that as Noel Coward sang famously was fit only for "mad dogs and Englishmen". But even if we keep ourselves covered and avoid the sun during summer, we still lose a lot of water through perspiration.

First perhaps a few words about all this heat and feeling hot business. The human body is like a furnace. At all times, the body is using fuel to produce energy. Even at complete rest, a lot of activity goes on including things like breathing and pumping blood. Also all the cells in the body are doing their thing. These activities produce heat that must be dissipated otherwise the body temperature will go up and the person will eventually die. If the surrounding temperature is much lower than the body temperature, the body will lose heat directly but even under such circumstances ‘insensible’ sweating or perspiration will go on to maintain body temperature.

As the temperature goes up around us, the body produces more sweat to lose more heat. Why? Because evaporation of the water in the sweat requires heat and that heat comes from the body. However, increased humidity and an absence of air circulation decrease the effectiveness of sweat induced heat loss. Increased air circulation due to a breeze or due to a fan facilitates heat loss because relatively cooler and drier air replaces air that has already been in contact with our skin and therefore makes us feel cooler.

The point then is that our body is losing water all the time and thirst is the indicator by which our body tells us that it needs to replenish the water it has lost. However, by the time we feel thirsty we are already slightly low in our body water, a condition that is called ‘dehydration’. If body water is not replenished then serious consequences will occur. In ‘normal’ conditions the body requires an intake of about two to three litres of water every twenty four hours. So, even during cooler months it is important to drink adequate amounts of water to keep the body working optimally. During summer the water requirement goes up. The same is true during periods of exercise or manual labour.

What then should we drink especially during summer months when we tend to lose much more water than in the winter? The first and the obvious answer is water. However there are many important considerations like how much water to drink and with or without things added to it. First thing to remember is that like everything else, too much water all at once can be dangerous. Even death has been reported in people that drank too much water at one go. So the best way to replenish lost water is to keep drinking it all along rather than at one go. Since the body tends to lose salt in the sweat, added salt might be necessary. Drinking ‘too much’ water is not a problem if done over a period of time. Extra water consumption just necessitates a few extra trips to the bathroom.

Drinking water however has problems especially in Pakistan. Most ‘tap’ water is probably not very safe to drink anymore and bottled water is often found to be equally unsafe. Of course certain brands of bottled water have been proven quite safe but sadly there is considerable possibility of substandard water being sold under the name of established companies. My advice and something that has been done in my house for the last many decades is that all the water that is used for drinking is first boiled then put in bottles that are kept in the refrigerator. Also, all the ice is made from this boiled water. Another added protection is to filter the water before boiling. A simple test might be to run the tap water through a folded clean white handkerchief for a couple of minutes and then see if a residue is left on the cloth. If there is a residue then either commercial filters should be used or else, clean muslin folded at least four time over can serve as a pretty decent filter to remove a lot of particulate matter.

If simple water is not pleasant enough to drink, diluted yogurt with a little salt or fresh lemon juice added to water and a pinch of salt and sugar or artificial sweetener does rather well. I usually fill up a few half litre bottles with the lemon drink and freeze the bottles. I then take one of these bottles with me to work and drink it as it melts. Any number of such drinks that are not too heavily salted or sweetened can serve the same purpose. I am opposed to commercially available fruit juices for three reasons. First, the amount or real fruit juice in them is questionable; second, there is a lot of sugar that has been added and third, they are too expensive. Fresh fruit juice if prepared at home is much better but even so, from a health point of view it is better to eat the fruit.

Another source of water replacement is fresh fruit and vegetables. Melons, especially water melons are a very pleasant source of water and a few other useful nutrients. Melons are almost eighty to ninety per cent water by weight. Cucumbers, lettuce, radishes, carrots and other such seasonal vegetables are also a good way to get water and added nutrition. Here of course it is important to remember that all these things except those that are peeled or are covered by a thick rind need to be washed well and in water that is also clean enough to drink.

Many people prefer not to use ‘iced’ drinks. That is a personal preference and has no health advantage. Unless of course ‘brain freeze’ is a problem for them. But for ordinary mortals like me, a bit of ice added to any drink on a hot day is a pleasant alternative. The important thing though is that the ice is made from boiled/filtered water.

Now to the bane of modern society, the ‘colas’ and such we drink. There is clear evidence that the frequent and widespread consumption of heavily sugared drinks is a contributing factor towards the existing epidemic of obesity and adult onset diabetes. Even the sugar free drinks are not quite safe in the long run. It is best to avoid all these drinks and preferably use the alternatives I mentioned above. However when eating out, these branded drinks can often be the best and the cleanest source of fluids available.

Tea and coffee though useful drinks should not be used for fluid replacement unless of course you are using tea in the Chinese style where the tea is really just boiled water flavoured with a few tea leaves and no sugar or milk has been added to it. As far as alcoholic beverages are concerned, undiluted drinks have the effect of making the body lose more water.