Sodium Supplementation, Drinking Strategies, and Weight Change
Marty Hoffman, MD
Dr. Hoffman is the director of research at Western States and a professor of Physical Medicine and Rehab at UC Davis. As Craig Thornley pointed out, Dr. Hoffman deserves a lot of the credit for the success of the research and studies coming out of Western States. While Dr. Hoffman is involved in many areas of research, he has become a world-leading expert in hyponatremia (water overload) during exercise. Dr. Hoffman has published research from Western States that has paralleled Dr. Noakes’s (the author of Waterlogged) research from Comrades. These two scientists have started to change the hydration paradigm at long-distance running events from one of “drink as much as you can” to “drink only to thirst,” in response to deaths worldwide cause by water overload among runners.
Some terminology to help digest this section:
Hyponatremia: Below-normal plasma sodium level, as determined by a blood test
Symptomatic hyponatremia: Below-normal plasma sodium level with outwardly visible related signs and/or symptoms
Hypernatremia: Above-normal plasma sodium level, as determined by a blood test
“Several companies have tried to make money selling table salt,” said Dr. Hoffman humorously, showing a slide of all of the brands of salt tabs available to runners on the market.
The average American consumes 3,500 milligrams of salt a day and we should only consume 500mg/day. But do ultrarunners need to take salt tabs during a 100-mile race like Western States?
The short answer is no. Sodium supplementation during an ultra actually has no significant effect on the blood level of sodium at the end of the race (Winger 2013). Runners who only drink to thirst and do not take supplemental sodium also maintain a normal (expected) body weight during a 100-mile run.
Dr. Hoffman showed data from 2011 where some runners actually ended Western States with hyper-hydration (they gained what is considered an unhealthy amount of weight) and had sodium levels that were above the normal range. These runners consumed between 25 and 60 S! Caps each. Dr. Hoffman and the Western States research team no longer pull runners for weight gain (as they have in the past) but now recommend runners should stop taking salt supplementation if they have gained weight.
The way I interpret these data taken together is sodium supplementation is not necessary to maintain normal sodium levels in ultramarathons, but can raise the sodium levels in the blood to an unhealthy level and something Dr. Hoffman did not mention, but concerns me, is that runners with elevated sodium levels and weight gain are at risk of having elevated blood pressure. That is certainly something runners with a history of high blood pressure, heart, or kidney disease should keep in mind.
From Dr. Hoffman’s talk on Day 2: Most runners with symptomatic hyponatremia tend to have gained weight while racing. This was seen in both his study at Western States and Tim Noakes’s study. Runners of 100-mile races are expected to lose between 4 and 5% of their body weight.
Behaviour among runners at Western States has changed between 2011 and 2013. In 2011, 44% of runners drank fluids on a schedule and not after thirst. In 2013, over 50% drank after thirst. Dr. Hoffman was pleased with this and believes this will cut down on the rates of hyponatremia at Western States.
Craving salt? Eat something salty.
Feeling bloated? Stop drinking.
He concluded by saying that it is actually very simple and people should, above all, listen to their bodies.