Hyponatremia - a cautionary tale (warning: long) (Read 1288 times)

Prehydrating by chugging 32 oz of water before a cool late Summer 10 miler is unnecessary and, as the OP pointed out, potentially dangerous.

Is it possible to get Hyponatremia during race or run conditions if you are sticking to the gatoraid / cytomax / etc and using gels to replace salts.

Assuming, of course, you've already been drinking water through out the day.

Basically, you need to replace two things you lose while running: sweat and calories. Sweat contains water and sodium chloride (i.e., salt) and very little else. Calories need to be replaced as carbs. Protein helps your muscles recover AFTER the run, so you don't really need it DURING the run. It is safe to run dry and to stay dry after the run. It is less safe to overhydrate. Most sports drinks contain a higher ratio of water to salt than sweat contains, so if you drink too much, you actually get too much water. For example, Gatorade Endurance Formula contains approximately twice the amount of sodium (200 mg/per 8 oz) of Gatorade Thirst Quencher to help meet the needs of athletes during prolonged exercise. 200 mg of sodium ~ 500 mg of salt. As before, there are 2200 - 3400 mg of salt per liter of sweat. Eight oz of fluid = 0.24 liters, and one liter is about 34 oz, or 4 1/4 x 8oz bottles. A liter of Gatorade Endurance, therefore, contains about 2125 mg of sodium, which is nearly within the range of sweat sodium concentration. Most sports drinks resemble standard Gatorade, so they have a lower amount of salt. But the lower amount of salt is only a problem if you drink too much over a sustained period. This can lead to a condition called hyponatremia. As I have previously posted: hyponatremia is a serious disease that merits watching out for. Hyponatremia is a condition in which you dilute your blood salt (sodium) with too much liquid, and it can be fatal (probably fewer than 1 marathoner dies every year from this). Fluids like gatorade and ultima still have far less salt than sweat, so drinking the same amound as you sweat can still dilute your blood. When extreme, hyponatremia causes weakness, hallucinations, lightheadedness and vomiting. Notice that these, except vomiting, are all the same symptoms as you would get with dehydration and with hypoglycemia. In a recent study in the New England Journal of Medicine, researchers found: On univariate analyses, hyponatremia was associated with substantial weight gain, consumption of more than 3 liters of fluids during the race, consumption of fluids every mile, a racing time of >4:00 hours, female sex, and low body-mass index. On multivariate analysis, hyponatremia was associated with weight gain (odds ratio, 4.2; 95 percent confidence interval, 2.2 to 8.2), a racing time of >4:00 hours (odds ratio for the comparison with a time of over 3:30 hours, 7.4; 95 percent confidence interval, 2.9 to 23.1), and body-mass-index extremes. (N Engl J Med. 2005 Apr 14;352(15):1550-6.) That means, the risk factors for hyponatremia include 1. a marathon time > 4 hours (compared to time < 3:30)="" 2.="" being="" too="" big="" or="" too="" small,="" 3.="" being="" female,="" 4.="" drinking="" over="" 3="" liters="" of="" fluids="" during="" the="" run,="" 5.="" gaining="" weight="" during="" the="" run.="" the="" researchers="" did="" not="" specifically="" look="" at="" the="" effect="" of="" ambient="" temperature,="" salt="" intake="" in="" the="" days="" leading="" up="" to="" the="" marathon,="" or="" whether="" drinking="" too="" much="" in="" the="" days="" leading="" up="" to="" the="" marathon="" contributed,="" but="" their="" study="" was="" performed="" on="" a="" hot="" day.="" remember,="" 3="" liters="" is="" nearly="" a="" gallon;="" the="" cups="" at="" the="" marathon="" were="" all="" about="" 4-5="" ounces="" full.="" there="" are="" 128="" ounces="" in="" a="" gallon.="" that="" means="" you="" would="" need="" to="" have="" drunk="" about="" 25="" cups="" of="" fluid="" in="" the="" 10="" aid="" stations="" to="" have="" gotten="" just="" that="" one="" risk="" factor.="" some="" experts="" suggest="" weighing="" yourself="" before="" every="" marathon="" and="" writing="" your="" weight="" on="" your="" race="" tag;="" that="" way="" if="" you="" pass="" out="" the="" medics="" can="" weigh="" you.="" given="" the="" variation="" in="" scales="" i="" do="" not="" know="" if="" this="" would="" actually="" be="" useful.="" folks="" with="" hyponatremia="" have="" too="" much="" fluid="" on="" board,="" so="" they="" pee="" clear="" urine="" frequently.="" folks="" who="" pee="" infrequently="" and="" who="" have="" darker="" urine="" likely="" do="" not="" have="" />