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Salt -The Missing Link to Performance Success?


Last updated: 23-Aug-18

By Renee McGregor
Performance Dietitian and Author of Training Food and The Fast Fuel Books.

Most runners are keen to enhance their performance, regardless of what distance they run or level they are at. They will research kit, training, nutrition and hydration and with so much information now available, it can be a bit of a minefield.

In reality, it is a combination of many factors from running technique, to training sessions and appropriate fuelling that will optimise running performance.

Nutrition for running and ultra running, in particular, is a controversial subject - with many evangilising ketogenic diets and others swearing by a more traditional high-carbohydrate intake. Similarly, when it comes to hydration and fuelling on the run, individuals have their processes and practices that they prefer to adhere to.

However, the one thing that most ultra-runners overlook is their intake of salt, or sodium to be precise. While most of you will understand the importance of taking on electrolytes, there seems to be little understanding of their actual role, purpose and importance.

It is well documented in scientific literature (Von Duvillard et al) that fluid intake and adequate hydration during exercise are essential and, more importantly, critical during prolonged training sessions and competition events.

The key role of fluid intake during ultra running is that it maintains:

  • hydration
  • thermoregulation (body temperature)
  • adequate plasma (blood) volume.

Ensuring that plasma volume and thermoregulation stay within an optimal range has a direct impact on performance. When core body temperature rises, due to dehydration, plasma volume decreases, resulting in an increased heart rate, which accelerates fatigue.

Just a 1% reduction in body weight through fluid losses can contribute to these negative physiological effects. In addition, dehydration has a marked affect on cognitive function, resulting in your inability to make decisions. During an ultra, this has been shown to cause runners to make navigational mistakes as well as reduce their ability to react to thirst and hunger requirements.

Whilst most runners are very conscientious about meeting their fluid intake, what they may not be aware of is the role of sodium. Sodium encourages and increases the absorption of fluid into the body, helping to maintain hydration.

So How Much is Enough?

Most runners will sweat between 400-2400 ml per hour of exercise, with the average value being around 1200 ml per hour, although this will vary with age, sex, weight, intensity of training and also the environmental temperature. These sweat losses are predominantly water but the main electrolyte lost is sodium.

The sodium content of sweat varies substantially from 115 to greater than 2000 mg per 1000 ml of sweat. A runner who is a “salty sweater” (i.e., has a high amount of sodium in their sweat) may lose well in excess of the recommended intake.

It is obvious, then, that in ultra running events and training, sodium losses may be very high. In temperatures of 20 Celsius, if a runner loses 1200ml of sweat in an hour and 900mg of sodium/L, then in an ultra race lasting five hours, their fluid losses will be in the region of 6000ml and their sodium requirements 5400mg. Therefore, they will require 1080mg of sodium per hour.

Most electrolyte tablets, salt capsules or energy drinks will only provide around 250-300mg of sodium. If you are diluting your electrolytes into 750ml, this will mean having to consume in the region of 2250ml of fluid per hour to meet your sodium needs, which is – practically -  very difficult, both from a consumption and transportation point of view.

Is it any wonder, then, why so many runners complain of the common symptoms associated with low sodium intakes and dehydration?

These include:

  • gastro-intestinal distress
  • nausea
  • bloating
  • fatigue
  • impaired concentration
  • dizziness
  • heat stress.

Indeed, the biggest cause of stomach issues during runs is related to sodium imbalance and not to the sports nutrition gel or bar that most runners blame. If your body is dehydrated, and you are consuming glucose, this will become highly concentrated within the gut. As blood flow is being directed away form the stomach to the working muscles, it cannot absorb this quick enough, resulting in stomach upsets.

As a rule of thumb, I generally suggest ultra runners need to take around 700-900mg of sodium an hour during longer training and competition. This can be a mix of salt tablets, electrolytes, energy drinks and even food.

Some good food suggestions include:

  • salted peanuts
  • mashed potato with cheese or marmite
  • cheese straws
  • cured meat.

Sodium balance and staying hydrated is not just confined to during running, it is equally important to think about it leading up to an event. I regularly recommend that individuals start drinking electrolytes in the 24 hours prior to race day.

Post race, restoring fluid losses is critical in replenishing glycogen stores. Being dehydrated will delay this process significantly and thus also affect how quickly you recover.

One of the best sources of post-race recovery is milk, as it provides hydration, carbohydrate, protein and also electrolytes in the correct balance for your body to absorb.

About the writer: Renee McGregor is a  Performance Dietitian and Author of Training Food and The Fast Fuel Books. There is more information on her website www.reneemcgregor.com

Further reading (click on these titles to download):

  1. Exercise and Fluid Replacement (American College of Sports Medicine)
  2. Hydration in Sport and Exercise (British Nutrition Foundation - Nutrition Bulletin)
  3. Dehydration and Rehydration in Competitive Sport (Scandinavian Journal of Medicine and Science in Sports)

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Your Comments On Salt -The Missing Link to Performance Success?

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01:03 08-05-18

Having read waterlogged and Andy's comments below, I want to say that the use of studies in general is to determine what the average response is to whatever is being is being tested. Extrapolating from that for general advice is fine, but saying things definitively like "x% of dehydration leads for performance loss" or "dehydration does not negatively impact performance" misses the actual person by person reactions. Many of the charts in waterlogged had random individuals way outside the normal range in all directions. I, for one, don't even know what "drink to thirst" means. When running I am rarely thirsty, especially when I get down 5% or more of my body weight. Does that mean I should just continue run for hours without drinking? I don't think so. My first sign of trouble is usually when I completely stop sweating. Nausea is usually right around the corner. My point is that using studies to find out what is generally going on does not mean everyone reacts the same.

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08:00 30-10-17

There are definitely a lot of strong (often very polarised) opinions out there regarding hydration and sodium supplementation for athletes.

Having read Waterlogged I appreciate that Tim Noakes presents what seems like quite a compelling case for the fact that sodium supplementation in particular has been over-sold as a necessary intervention for all athletes.

His point is almost certainly very true for most athletes doing shorter events where sweat and salt losses are relatively limited as the need for supplementing with extra salt over and above what is in the normal diet is probably largely unnecessary.

However during longer - particularly ultra distance - events and any time when sweat losses are very high (e.g. during days of consecutive heavy training) salt and fluid intake can become a hugely important issue, especially for any athletes whose sweat and sodium losses are higher than average.

There is a solid body of both scientific and anecdotal evidence to support this idea even if Noakes and some others don't agree with it.

As an example a recent study of athletes competing in a real world half ironman distance triathlon showed very significantly improved performance with salt supplementation when compared with a group who were given a placebo instead:

Regarding the specific comment that plasma volume is unrelated to thermoregulation and performance this is worth a read that provides some evidence to the contrary

When it comes to the possible role of sodium in cramping this is an excellent (balanced) article that highlights the fact that whilst cramping is definitely not just linked to electrolyte imbalance, there is still a very strong case to support the idea it can be implicated (along with masses of anecdote from the real world that demonstrate this)

In fact when you look at those that are leading in this area of research, Burke, Sawka and Shirreffs, they all indicate that sodium and dehydration have a significant part to play in performance, especially when we think about ultra distance events and the fact that a huge percentage of the population at these races are not elite level.

I think a really important overall point to make here though (and what the above 3 papers show) is that fluid and electrolyte replacement is still an area that is incompletely understood in sports nutrition - especially with regards to ultra distance events - and that there are a lot of strong, contradictory opinions and evidence in the field leading to different people coming to some very different conclusions.

Authors like Tim Noakes and Martin Hoffmann represent one quite extreme viewpoint - that zero sodium supplementation and drinking water alone to thirst no matter how much sweat and salt you lose is all you need to do. (What even if you're losing litres of sweat and grams of sodium?)

At the other end there have been years of sports drink marketers telling people that we all need electrolytes, all of the time no matter what we're doing to maintain performance. (What even if you're just going for a 5km jog around the park?)

As with most things in life the truth usually resides somewhere between two extreme viewpoints in a sensible middle ground. A lot of what is true for you will depend on your own individual needs (as the article points out) which can vary dramatically from person to person.

As a performance dietitian I can only base my advice on the evidence that is available and this is exactly what I have done in this instance. I have looked at all the facts, including the papers you have stated and provided the most practical guidelines for the audience I was writing for.

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04:04 27-10-17

This article like most regarding salt is full of myths and is an appalying distortion of sciewnce and ignorance of what really occurs in athletes in ultras .

Lets take the basic three premises mentioned
"The key role of fluid intake during ultra running is that it maintains:
thermoregulation (body temperature)
adequate plasma (blood) volume":

Studies on real athelets show that
a) dehydration does NOT negatively impact performance if you drink to thirst - not one study has ever proven a link between a fluid loss of more than 2% and a reduction in performance - not one .
If thats the case then the focus should be on drinking to thirst NOT keeping hydrated
b) body temperature and ovcerheating is NOT related to hydration status
c) a reduction in blood plasma volume does NOT negativelty affect performance - it does change things yes but without afecting performance.

"Just a 1% reduction in body weight through fluid losses can contribute to these negative physiological effects" - this is dangerous and 100% incorrect. Explain how elite runners are regularly 5-10% dehydrated and breaking world records !

The suggestion to take in almost a gram of salt per hour is ridiculous - in a 24+ hour event thats opver 24 greams of salt - completely uneccessary

Sodium intake in races is NOT related to reduced risk of stomachproblems or hyponatremia or cramping or heat stress .

There is no scientific reason to consume salt in ultras

I could quote hundreds of studies but you canjust readwaterlogged instead but I'll leave on to summarise things


When we stop looking at sodium as the cure all for all of our woes in ultras and start looking at the real causes like specific training , good pacing etc which arent the easy cure that a salt tab is the better your perfoprmances will become.