How Much Water Are You REALLY Supposed to Drink?

Photo (cc) by Matt and Kim Rudge

You know how you’re supposed to drink eight glasses of water a day? Actually, it might be healthier to drink less. At least for women.

We know drinking more water than your body can process might kill you. So might heat strokes if you don’t drink enough. So what’s the right amount to avoid a trip to the hospital?

A drop in the bucket

A newly released study from Murad Research Labs on women’s hydration levels suggests the ideal may be to drink two glasses a day and instead eat more raw fruits and vegetables (which contain water that stays in your system longer) as well as additional nutrients.

“In a nutshell, eight glasses of water means eight trips to the bathroom, flushing the system of vital nutrients and minerals,” says Howard Murad, the doctor who directed the study. “Monitoring tens of thousands of subjects, we’ve seen that colorful raw fruits and vegetables are actually the best form of water for our cells.”

This particular study didn’t include “tens of thousands” – only 104 women. (They’re planning a follow-up study looking at more than 4,000 men and women later this year.) But by measuring hydration at the cellular level, the study seems to suggest the fountain of youth’s secret might be sips instead of gulps. It found that women in their 40s who drink just a glass or two a day are as hydrated as average women who are 10 years younger.

But those who drank seven or eight cups a day actually had hydration levels more than a percent lower than those who drank two cups – which is apparently a lot, even though it doesn’t sound like it. The “average intracellular water level” for women in their 40s is 24.6 percent, while those in their 30s have 25.4 percent.

What others say

Given the small scale of the study – and the fact its results are only for women – it seems worthwhile to compare Murad’s findings to what others have suggested. Here’s Mayo Clinic, one of the best-ranked hospitals in the country…

How much water should you drink each day? It’s a simple question with no easy answers. Studies have produced varying recommendations over the years, but in truth, your water needs depend on many factors, including your health, how active you are and where you live.

They say there’s no “hard evidence” for the old eight-cups-a-day advice, but their baseline is the Institute of Medicine’s recommendations, which are actually higher – about 3 liters (13 cups) a day for men and 2.2 liters (9 cups) for women.

But that includes all fluids, including those in foods, not just water…

On average, food provides about 20 percent of total water intake. For example, many fruits and vegetables, such as watermelon and tomatoes, are 90 percent or more water by weight.

If food covers 20 percent, that means guys should get 10 cups and ladies seven. Subtract the juice, tea, coffee, milk, and soda you consume, and you’re probably good.

They note exercise, heat, sickness, pregnancy, and breastfeeding may require more water, but conclude you shouldn’t fret about it. If you “rarely feel thirsty and produce 1.5 liters (6.3 cups) or more of colorless or light yellow urine a day, your fluid intake is probably adequate.”

No need to measure. A 2009 Scientific American article also examined the myth, looking at where it came from – which is the Institute of Medicine (yes, the same one the Mayo Clinic cites) from 1945. Alas, its dietary guidelines didn’t account for the water in food. In 2004, the Institute changed its mind, concluding, “the vast majority of healthy people adequately meet their daily hydration needs by letting thirst be their guide.”

The bottom line

So there you have it: Drink when you’re thirsty. But whatever amount you end up drinking, there’s no need to pay $6.40 a gallon for bottled water. A lot of it is just filtered tap water, and you can get those filters for under $20.

Disclosure: The information you read here is always objective. However, we sometimes receive compensation when you click links within our stories.

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