Part 2: Sweat, Salt and Minerals

What originally sparked interest in creating this 2 part series was the then-upcoming Centurion race in Collingwood.  As you may have noticed, I strategically posted only the 1st part prior to the race.  Shockingly, this strategy did not work as lots of fast guys still destroyed me.  Maybe they have race secrets they should be blogging about!  Nevertheless, a great day on the bike.  Check out Larry Bradley's race report to get a sense of what it was like to participate in the event.

When you ride for almost 5 hours over the course of 172km, fluid and salt balance undoubtedly play a vital role in maintaining performance.  The easiest way to waste valuable training is to refrain from taking in adequate amounts of either.  Last week's blog addressed how to maintain proper fluid balance, while today we will look at the salt.

Sodium

This is the mineral that is lost the most as we sweat.  As with everything else, there is obviously variation between athletes, but on average we lose about 1500mg per 1L of sweat lost.

So what happens if we lose too much sweat?  Well, the sodium outside of our cells will eventually be at a much lower concentration than the electrolytes inside our cells.  As a result, our body tries to balance things out, allowing water to travel into our cells.  As the cells fill up with too much fluid, early symptoms such as disorientation and shortness of breath can take place leading to more serious complications such as coma and even death.

As a general rule of thumb, you should consume 1g of sodium for every 1L of fluid you consume.

Fortunately, sports drink companies typically have this figured out, and their products meet this criteria.

Potassium

Contrary to what a lot of information out there shows, potassium is not an absolute requirement during athletic events.  It is easily replenished via the regular consumption of fruits, vegetables or fruit juices. 

While sodium is the main electrolyte located outside of cells, potassium is the main electrolyte within cells.  This is essentially why it is lost to a much lesser degree while sweating.  Potassium debt is a rare occurrence, and it is typically only seen in those who are malnourished or who are suffering from chronic diarrhea or related conditions.

Other Minerals

Just because we are on the topic, I would also like to remind people to keep a close eye on three very important minerals: calcium, magnesium and iron.  While these minerals are not lost in sweat, athletes who undergo strenuous training are much more susceptible to developing deficiencies.  Calcium and magnesium are both imperative for building and maintaining strong bones, while iron is a key component of the oxygen-carrying hemoglobin within our red blood cells.  Low levels of any of these three minerals can therefore result in osteopenia and anemia.

To prevent this from happening, ensure that you are consuming at least 1000mg of calcium per day (depending on your age and gender) with at least 600 IU of vitamin D.  Magnesium is found in an array of foods including nuts, grains and green leafy vegetables.  The recommended daily allowance is about 400mg/day, and a well balanced diet is usually sufficient in achieving this.  Iron balance is a more complicated issue due to the variation seen based on age and gender, but a well balanced diet high in meat or meat substitutes will help ward off its deficiency.  For more details on iron, see the National Institute of Health website.  In general, you should pay attention for symptoms such as chronic fatigue and stress fractures as a mineral deficiency may be at play. 

Closing 

So, in the end, the only mineral you really need to worry about on race day is sodium.  A healthy, well balanced diet plays an important role in maintaining adequate mineral levels within your body on a more long term basis.  BUT, on race day, remember:

1g of sodium for every 1L of fluid you consume.

Next time we will be switching gears a little bit, and will be looking at the effects of exercise on the brain.  Until then!

References:

1) Frissell, RT, et. al., 1986. Hypoenatremia and ultramarathon running. JAMA. 255: 772-774.

2) National Institute of Health: Office of dietary supplements. http://ods.od.nih.gov/ Accessed Sept 27th, 2011

3) Nutritional Aspects of Athletic Performance, Dr. James Meschino D.C., M.S., ND, 2008, Pages 20-24