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Health Answers

Will increased water consumption flush excess sodium from the body?

By Courtney Humphries
January 31, 2011

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Q. I eat far more salt than I should. If I drink a lot of water, will that flush the sodium out of my system?

A. “That would be nice, wouldn’t it?’’ says Jonathan Williams, a physician in the Division of Endocrinology, Diabetes, and Hypertension at Brigham and Women’s Hospital. Unfortunately, he says, the total salt you consume has an effect on your body. You can’t simply dilute it or flush it out with water.

In a perfect world, your kidneys would simply remove any excess salt from the blood and excrete it in the urine. But it’s not that simple. “The body’s been tuned for eons to hold onto salt,’’ Williams says, because a little bit of salt is vital to your body’s functioning, and salt hasn’t always been as abundant in the diet as it is now.

Several hormones are involved in regulating the amount of water and salt in the blood, and they don’t always keep excess salt out of the bloodstream when you eat too much salt. When some people eat a high-salt diet, their kidneys don’t remove all the excess salt, so it builds up in the blood. Salt attracts and retains water, so excess salt causes the volume of water in the blood to rise, which raises blood pressure. Williams says that in about one-third of people with normal blood pressure, eating a high-salt diet causes their blood pressure to rise.

In this scenario, salt is dangerous in part because it leads the body to retain water. So drinking even more water will only exacerbate the situation, not alleviate it.

In the relationship between salt, water, and blood pressure, salt is the factor that you can manipulate to prevent blood pressure from rising. Current dietary guidelines recommend a maximum intake of 2,300 milligrams of sodium per day. This month, the American Heart Association issued a statement calling on Americans to limit salt intake even further to 1,500 milligrams per day, because of its potential to elevate blood pressure and increase risk of stroke, heart attacks, and kidney disease. That’s a steep drop from the average American diet, which packs in 4,000 milligrams of salt per day.