While it’s unlikely to be a problem at Saturday’s Kansas City Marathon, Lewis Maharam wants runners to know they should avoid overhydrating.

In fact, Maharam, who is medical director of a number of marathons across the country, including the New York City Marathon, believes you shouldn’t listen to your elders.

“You shouldn’t be drinking like grandma says, ‘drink, drink, drink, drink,’ ” Maharam said in a phone interview. “No one in the history of the world has died of dehydration. There’s not one reported case.

“But there are many cases of people who overdrank. Overdrinking is way more dangerous than underdrinking.”

That’s because too much fluid intake (particularly water) can lead to hyponatremia, which is a potentially fatal condition.

At least four marathon runners have died from hyponatremia-related trauma since 1993, according to the San Diego Union-Tribune.

When you run long distances, blood in shunted to the legs and less blood flows to the kidneys. Salt regulatory hormones increase, which causes an athlete’s kidney to concentrate their urine with salt and retain free water.

Hyponatremia is a reduced blood sodium concentration. When the sodium level falls below 129 millimoles per liter, it can create a general clouding of consciousness not unlike the slowing of brain function. And that’s considered a mild case.

The more water you drink, the more it falls.

“As you continue to drink, you’re just continuing to lower your total serum sodium, you’re diluting yourself,” said Maharam, who writes the “Ask the Running Doc” column in runnersworld.com. “Studies have shown that if you stopped at every water station along the course — and most of them have them every mile — and you drink one cup of Gatorade, you’re dead by the time you finish. Or your serum sodium is really low.

“Your body fills up with fluid, you get pulmonary edema and your brain starts to swell.”

While the weather forecast Saturday calls for frosty temperatures, it’s still worth knowing about this condition.

Maharam has some tips for avoiding hyponatremia:

•Follow the fluid recommendations. Drink only for thirst: Not more than one cup every 20 minutes.

•Try not to drink more than you sweat.

•Favor a sports drink that has some sodium in it over water, which has none.

•In the days before the race, add salt to your foods (provided that you don’t have high blood pressure or your doctor has restricted your salt intake).

•Consume one salt packet at the start. Carry a small salt packet with you, and during the last half of the race consume that second packet.

•After the race, drink a sports drink that has sodium in it and eat some pretzels or a salted bagel.

•Stop taking non-steroidal anti-inflammatories 24 hours before your race and do not start again until a minimum of 6 hours after finishing the race.

---