It’s a common sight in gyms: guys and girls hauling a gallon jug of water everywhere.

And you can understand why, given people are often told: ‘If you’re thirsty, it’s too late because you’re already dehydrated.’ Understandably, it’s better to err on the side of caution because of the negative impact dehydration has on performance and muscle growth. But is lugging so much water warranted? And what is the actual optimum daily amount?

It’s became the norm for everyone to force themselves to drink a gallon of water. Because in 1997 the American Institute of Medicine introduced the dietary reference intake (DRI) and recommended males drink 3.8L of water per day and females 2.7L.

However, a quick visit to a local gym will more often than not reveal innumerable women drinking from a gallon container of water, which at 3.78L is one above their recommended DRI.

But it’s not just women who regularly drink too much water and here’s why.


1. Caffeinated drinking don’t count

There’s a misconception that if a beverage contains caffeine, it shouldn’t count toward your daily H2O. However, two separate studies by a Dr AC Grandjean and associates showed no significant differences in the effect of various combinations of beverages, whether caffeinated or not, on the hydration status of healthy adult males. Thus if you’re consuming coffee or tea, this can be counted towards your daily total.


2. If you’re thirsty, you’re already dehydrated

Many scientists disagree with this, and with good reason. Simply put, when we drink too little water our blood thickens, thus bringing us closer to dehydration. But when that happens our bodies secrete the hormone vasopressin to retain what little fluid there is.

A thickening of the blood by less than 2% can lead to us feeling thirsty, but the vast majority of experts would advocate that the onset of dehydration occurs when a person has lost 3% of their bodyweight, which translates into the blood thickening by 5%.

This suggests that feeling thirsty doesn’t mean you are dehydrated; however, it doesn’t mean you should forget water.


3. Food doesn’t count

This is another very common misconception because according to the DRI: “All sources can contribute to total water needs: beverages (including tea, coffee, juices, sodas and drinking water) and moisture found in foods. Moisture in food accounts for about 20% of total water intake. Thirst and consumption of beverages at meals are adequate to maintain hydration.”

For example, one medium apple contains 4oz of water. What you eat makes a significant contribution to your daily water intake, and again suggests drinking one gallon of water a day isn’t essential.


How much should you drink then?

Unfortunately there isn’t a definitive optimal amount. The aforementioned DRI recommendation of 3.8L and 2.7L is actually based on research conducted in the US during World War II, and has too narrow a subject base.

You can’t expect a man of Middle Eastern descent to have the same water requirement as a man from Alaska.

This is one reason high water intakes shouldn’t be recommended universally. It seems stupid for a 160lb man to drink the same amount of as a man that’s 225lb, even if they’re both from the same place.

Likewise, it doesn’t make much sense for a 125lb woman to drink a gallon of water.

In other words, the amount of water you drink shouldn’t be based on just the climate of the country you live in or the intensity of your exercise regimen, it should also take into account your bodyweight.

An individual needs a certain amount of calories to maintain their weight, thus I’m inclined to prescribe the 1ml/kcal/day rule some clinicians advocate. This would mean if you are consuming 3,000 calories, you need 3L of water, excluding the amount consumed during training.

Alternatively, you can weigh yourself before and after your training session to determine how much weight you lost while working out. This allows you to calculate your required daily water intake to maintain your training schedule. But remember, this should be added to your daily total of 1ml/kcal/day.


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