If you’re like most of us, you probably carry a water bottle around with you most everywhere you go, not just when you’re headed out for a hike or the gym. It seems Americans have been taking to heart the message that 8 glasses of water a day are great for your health, not to mention your waistline. But is it true?
Well, no … and yes.
No, because the old adage about drinking eight glasses of water is simply not based on any scientific evidence. In fact, that advice has comes from one man who wrote a 1921 research paper based on measuring his own output of urine and sweat. From this he calculated that he lost approximately 3% of his body weight—or about 8 cups—in water through the course of a day. And from this one person’s single experiment sprang the overarching advice that all humans around the globe should drink 8 glasses of water a day!
Yes, because the despite the fact that water consumption is not nearly as well researched as it should be, there have been a few impressive studies showing that simply by consuming enough water each day, you might dramatically reduce your risk of a large array of serious health problems, ranging from:
- Falls and fractures
- Heat stroke
- Heart disease
- Lung disorders
- Kidney disease
- Kidney stones
- Bladder and colon cancer
- Urinary tract infections
- Dry mouth
- Decreased immune function
- Cataract formation
The question is, how strong is the link between more water and better health? And if the link is solid, how much water is ideal? Read on to find out!
Water Reduces Risk of Bladder Cancer
One of the best quality studies showing a strong link between drinking more water and better health was a Harvard study of 48,000 men finding that risk of bladder cancer decreased by 7% for every extra daily cup of fluid the men consumed. This benefit remained even when the researchers controlled for other health risks and benefits such as diet and exercise.
“Therefore,” wrote Dr. Michael Greger on his blog, NutritionFacts.org, “a high intake of water—like 8 cups a day—may reduce the risk of bladder cancer by about 50%, potentially saving thousands of lives.”
Water Cuts Risk of Dying of Heart Disease in Half
Another impressive study of the effects of water intake is the Adventist Health Study of 20,000 men and women. In this study, about half of the subjects ate a vegetarian diet, and so likely consumed extra water through fruits and vegetables.
Those who drank 5 or more glasses of water a day had half the risk of dying from heart disease compared to those who drank 2 or fewer glasses a day.
Source: Adventist Health Study
As was the case with the Harvard study, these benefits held up even when the researchers controlled for other health factors such as exercise and diet. “These data suggest that it was the water itself that was decreasing risk, perhaps by lowering blood viscosity (blood thickness),” wrote Dr. Greger.
How Much Water is Enough?
Drawing from all of the best available evidence, experts from our country’s leading health organizations such as the U.S. Institute of Medicine as well as the World Health Organization and European researchers all recommend the following daily intake of water:
Women: 8 to 11 cups
Men: 10 to 15 cups
If that sounds like a lot, remember that this total can include water from all sources, including food, especially raw fruits and vegetables, which are high in water. Therefore, it’s likely that most women would still reap benefits from drinking 4 to 7 cups of water a day and men 6 to 11 cups. Important to note is that all of these recommendations are based on moderate activity and temperatures, and would need to be increased, perhaps by a lot, with exercise and/or hot weather.
Meanwhile, to think that simply by making sure to drink enough water every single day, you can slash your risk of at least one type of cancer as well as death by heart disease, and quite possibly a wide range of other serious health issues, at zero expense and no side effects. With that in mind, we cannot imagine a reason not to keep that water bottle full!