Longevity and good health as one ages have long been linked to a mythical “Fountain of Youth.” The imagery, it turns out, may not be wrong.

A National Institutes of Health study published this week in the journal eBioMedicine finds that drinking enough water is linked to better biological aging and reduced risk of both chronic disease and premature death.

Researchers took data collected over 30 years from 11,255 adults to look at links between serum sodium levels and different health indicators. When people are adequately hydrated, their serum sodium levels are lower than when they are not. They found that adults who had sodium levels on the high side of normal in their blood more often developed chronic conditions and aged faster than those with lower serum sodium levels. And more of them died younger, too.

“The results suggest that proper hydration may slow down aging and prolong a disease-free life,” said Natalia Dmitrieva, a study author and researcher in the Laboratory of Cardiovascular Regenerative Medicine at the National Heart, Lung, and Blood Institute, in a news release about the study.

The data was taken from the Atherosclerosis Risk in Communities study, in which participants made five medical visits — the first two in their 50s, and the last between ages 70 and 90. For this study, researchers excluded those who had either high blood sodium initially or who had medical conditions like obesity that could affect those levels.

According to CNN, “The authors thought optimal hydration might slow down the aging process, based on previous similar research in mice. In those studies, lifelong water restriction increased the serum sodium of mice by 5 millimoles per liter and shortened their life span by six months, which equals about 15 years of human life.”

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To determine biological aging, they looked at 15 health markers, including systolic blood pressure, cholesterol and blood sugar, all indicators of how well one’s heart, lungs, kidney, metabolism and immune system work. They also adjusted for factors like age, race, sex, smoking status and high blood pressure.

Those with serum sodium in the high normal range more often showed signs of faster biological aging, seen through indicators like metabolic and cardiovascular health, lung function and inflammation. Those folks tended to be biologically older than their chronological age, compared to those with lower levels of serum sodium. Those risks increased as the serum sodium levels climbed — including increased risk of premature death.

Higher serum sodium levels could be used to “predict faster rate of the biological aging, and an increased burden of chronic diseases later in life, including heart failure, dementia, chronic lung disease, stroke, diabetes, peripheral vascular disease and atrial fibrillation,” the study said. 

Association, not causation

The findings don’t prove cause, however, according to the researchers, who note that more study is needed “to determine if optimal hydration can promote healthy aging, prevent disease and lead to a longer life.”

“The goal is to ensure patients are taking in enough fluids, while assessing factors, like medications, that may lead to fluid loss,” said Dr. Manfred Boehm, a study author and director of the Laboratory of Cardiovascular Regenerative Medicine, in the release. “Doctors may also need to defer to a patient’s current treatment plan, such as limiting fluid intake for heart failure.” 

Earlier studies have suggested that about half the world’s population doesn’t drink enough water daily.  

“On the global level, this can have a big impact,” Dmitrieva said. “Decreased body water content is the most common factor that increases serum sodium, which is why the results suggest that staying well hydrated may slow down the aging process and prevent or delay chronic disease.” 

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Some pushback on findings

Will water solve all your health problems? Probably not. As NBC News reported, “The relationship between drinking fluids and age-related chronic diseases remains ‘highly speculative,’ said Dr. Lawrence Appel, the director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins University. He said the study ‘doesn’t prove that drinking more water will prevent chronic disease.’”

Appel suggests it would take serum sodium levels outside the normal range — those that come with actual dehydration — to cause serious health impact.

“He also cautioned that many factors besides hydration can influence a person’s blood-sodium level, such as taking diuretics, also known as water pills, for high blood pressure. Some people with neurological issues or other disabilities may also have higher-than-average blood-sodium levels, Dr. Mitchell Rosner, the chair of the University of Virginia Department of Medicine, said in an email,” per the NBC News article.

How much water?

It’s not just water that provides hydration. And how much someone needs depends on a lot of factors. According to The Washington Post, “Age, body size, climate, activity level and lifestyle all influence how much water your body really needs.”

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The article notes a new study in the journal Science, “which found that for most healthy adults, drinking eight cups of water a day is completely unnecessary. The advice is misguided in part because it doesn’t take into account all the water that we get from our food and from other beverages like coffee and tea. The research found that our water needs vary from one person to the next.”

Eight glasses of water won’t hurt you, by the way. Excess fluid is excreted in urine. You have to drink a lot to cause harm unless you have a medical condition like heart failure that leads to water retention.

So how much should people drink? Herman Pontzer, a professor of evolutionary anthropology and global health at Duke University and a co-author of the Science study, told the Post that people should drink when they are thirsty, but to limit or eliminate sugary drinks. And to remember that foods provide water, as well.

“If you’re paying attention to your body and drinking when you feel like you need to, then you should be fine,” Pontzer told The Washington Post.

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