Too Much Water? Not Enough Salt? Hyponatremia in Marathon Runners

wetlands

Hyponatremia (low sodium, or “water intoxication”) is a risk for runners with atrial fibrillation. It is certainly a risk for me and I believe I have experienced it a number of times in the past. Personally, I am much bigger than most marathoners (6’3” 205 lbs), and because of that and the atrial fibrillation, much slower – so I’m out there twice as long and sweating twice as much. Plus – over the years it has been drilled into all of us to make sure we drink enough water.

Ironman athletes, ultrarunners, and bigger runners are all at increased risk because we are simply out there for much longer periods of time. Women athletes tend to be at higher risk for hyponatremia – it has been found that women hydrate more during a race.

Drinking enough water is a good idea – but it needs to be accompanied by increasing salt intake.

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Normal levels of sodium are about 135-145 mEq/L. Symptoms are likely to begin at 130 or lower and if you get below 120 the condition may become fatal. While there are a number of medical causes for hyponatremia marathon runners fall into the category of consuming too much water and not enough sodium, and sweating out valuable sodium. Think of the white dried salt on your temple or on your hydration pack straps after a long run.

Symptoms include bloating, headache, swelling (check to see if your ring or wristwatch seems to be getting tight), nausea, vomiting and eventually weakness, restlessness, confusion, and well . . . it just gets worse from there. It is particularly problematic for runners because some of the symptoms (headache, nausea, cramps, and dizziness) are the same symptoms for dehydration so the impulse is to drink more water – which of course makes it worse.

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There is currently an ongoing study at the Houston Marathon involving volunteers who are followed closely, weighed, fluid intake measured, lab studies obtained, etc. The study found that runners with lowered sodium levels drank more water, retained more water than normal volunteers, and they lost more total sodium and had saltier sweat.

Runners who were dehydrated but not hyponatremic had higher heart and respiratory rates, felt worse, and had lower blood pressure than hyponatremic runners. The hyponatremic runners felt better, but had more nausea and bloating.

What can be done?

Drinking less water is sometimes recommended but it is difficult to do when you are used to drinking a lot of water while running. I’ve tried drinking less water during a marathon and frankly I think it made things worse. Also some runners can become hyponatremic without over-doing the water consumption.

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Weighing yourself frequently along the course and looking for weight gain (water retention) has been recommended – YEAH RIGHT! How is this going to happen?

Personally I try to drink water with sodium supplemented (NUUN, GU Brew), and try grabbing some little pretzels at aid stations (if available); but some research suggests this might not always be helpful.

“Watch out for feelings of confusion, nausea, fatigue, and particularly vomiting and swollen hands and feet. If you experience these, seek medical help.”

Fatigue? Really? Fatigue during a marathon – you don’t say? Isn’t that generally a part of the experience?

I don’t have a good answer. I know I’ve had problems with this – I’m clearly in the high risk category for hyponatremia. I also generally have particularly poor races if it is a warm day.

My interventions include

1.) Drinking enough water
2.) Electrolyte supplements in my water (NUUN, Gu Brew)
3.) Additional electrolyte supplementation (SaltStick caps, Endurolytes caps, little pretzels)
4.) Making sure I have a salty snack or meal after a race or long run
5.) Trying to dress so I’m a little cool rather than a little warm

I’d love to read your suggestions – please leave a comment if you have any experience with hyponatremia and suggestions as to how to avoid it.

Update (March 13, 2014):

I found this terrific article posted on Twitter by Dr. Larry Creswell. The key points are quoted below.

KEY POINTS

Most medical scientific organizations recommend low or moderate sodium diets to the general population in order to reduce the risk of high
blood pressure (hypertension).

Regular physical activity reduces the risk of hypertension.

Athletes lose sodium in sweat during exercise. The amount of sodium that is lost during endurance exercise depends on the sweating rate and
the concentration of sodium in the sweat. In turn, sodium loss during exercise depends on individual factors, such as genetics, fitness and heat
acclimatization, as well as the type, intensity and duration of exercise and the external environment.

Sodium ingestion by endurance athletes does not typically increase blood pressure, so low sodium diets are not recommended for individuals
who participate in long-term aerobic exercise.

Sodium ingestion during or following endurance exercise will help to stimulate thirst and drinking as well as stimulate fluid retention by the kidney.

No athletes are immune to hypertension, so athletes should monitor their blood pressure as they do their general health. This is particularly
important for older athletes, athletes with a genetic predisposition to hypertension, stroke or other cardiovascular disease.

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Heat and Salt and A Fib

As stated previously I get pretty lightheaded when I get up from a sitting position after a hard workout, particularly in hot weather. Orthostatic hypotension. I don’t know why I get dehydrated so easily now, but I have learned that I need to eat something salty and drink a lot of water  after a workout, particularly a run or a bike ride which is longer than an hour or two, otherwise I get pretty dizzy when I first standup, and I’ve had a friend who is an nephrologist and another friend who is an internist both tell me to make sure I drink plenty of water after a workout and get some salt. Just one more fun aspect of being in persistent atrial fibrillation.

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Pre-Race Motel

This is the first time in my life I’ve ever actually been trying to get more salt. Most people spend their lives trying to avoid salt. I have started bringing potato chips for a post run snack to the trailhead for my long runs. Another great post run snack is some blue corn chips with some hummus with some Hoisin sauce.

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Pre-Race

Although it is neither here nor there, I’d like to state that I am a vegetarian (nearly vegan – if not for the occasional veggie pizza) as far as diet is concerned.

I also find that I am more sensitive to heat, which is obviously related. Last summer I would often start to feel pretty tired 17 miles into a 20 mile training run. In cool weather a 20 mile trail run is no problem. When I’m training for a 50K I basically try to do a 20 mile run every weekend.

Fortunately I live in Klamath Falls, on the East side of the Cascades of Oregon, where we have relatively cold Winters and generally cool Spring and Autumn. Summer, obviously, can be pretty hot – but nothing like Southern California, Arizona, Mexico, the South, etc.

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Resting During a Trail Run

I have also noticed over the past several years that I did quite poorly during marathons if the weather got hot. The concept of hot weather is a relative term – for me anything over 70°F (21°C) would be considered hot. My ideal running weather would be 35 to 55°F. Ten years ago I could do a 20 mile run when it was 90°F (32°C) without much problem. Those days are over.

I’d be interested in hearing from other people with atrial fibrillation with respect to this. Please comment.

ringotired

Ringo – Pooped Out After a Long Trail Run