Hydration is a hot and sweaty topic right now and I’ve talked about it in previous blogs, mostly to say that you should drink to thirst. But should you really in all cases? And what about electrolytes? Here is a lowdown about the debate of the moment: to drink or not to drink, to salt or not to salt? That is the question.
There are two main lines of thought out there. One lead by Pr Tim Noakes who claims in his famous book Waterlogged published in 2012, the followings:
-We are able to regulate our blood sodium concentration very tightly and we have enough reserve in our body to supplement sodium losses in even very long endurance event.
-Being dehydrated is not a detriment to performance as the winners of marathon often have up to 10% body loss. Therefore drinking to thirst is a very valid approach.
So there you have it, one end of the spectrum where it basically says that you are going to be fine if you drink to thirst and electrolytes are not necessary because we have so much salt in our body that it is enough to get us through even an Ironman.
In fact, Pr. Noakes published a paper entitled: sodium supplementation is not required to maintain serum sodium concentration in Ironman triathlete. In this paper, he looked at IM athletes and their sodium intake versus performance and blood sodium concentration. While he did not see any difference between the groups for blood sodium concentration, muscle soreness and performance, there is still a reduction in muscle soreness in the experimental group however not significant. Also, if you read carefully (and that is why you should never just read the abstract and jump to conclusions), you are going to notice that the experimental group did not take a lot of sodium at all, maybe 300 mg/hour which might not be enough as you will see.
Then there is the other end of the spectrum represented by the American College of Sport Medicine (ACSM) who were recommending in the 1990s to drink about 600ml to 1.2L per hour of fluid with electrolytes to sustain performance, based on some more or less valid studies a lot of them funded by the Gatorade Sport Science Institute (GSSI, ahem). They also claim that a 2% dehydration leads to overheating and decline in performance.
Following these recommendations, there was at the same time a resurgence of athletes that showed hyponatremia during races, a dangerous condition where there is a decline in blood sodium concentration that can even lead to death. Correlation or causation? One thing to note is that those who were afflicted by that were middle of the pack runners who were actually GAINING weight over the course of a marathon because they often drank a lot of water on the higher side of the recommendation. Elite runners would not get subjected to that because most often they would drink much less. Let’s face it, have you ever tried to drink while sprinting? Pretty hard. So yes that is why most elite lose a lot of water, but they still do very well. Could they do even better if they had an IV in with fluids while running? Maybe! But that would be pretty hard to do and that study has not been done yet and I don’t know if it will!
Is the salty sweater a myth?
The thing is that we are all salty sweater, because we all sweat sodium. But one thing is sure, there is a lot of variability in sodium losses among people (see graphs below from a poster from Coyle’s lab funded by the GSSI of course). This figure demonstrates the sodium loss of athletes during a moderate intensity 30min spin in the heat. As you can see, it varies enormously. Most of this variation is regulated by our genes. It is even reported that if you are the carrier for Cystic Fibrosis you may be losing more sodium to sweat than not and this mutation is not as uncommon as we think. It will also vary with heat acclimatization, altitude and sodium intake in diet.
Let’s say that highest sodium losses are at about 140 meq/hr, that is 3.2g/hr (!!!) that is quite a bit of sodium. Most people will be at around 35mEq/hr or 800 mg/hr.
But won’t taking salt help with cramps regardless?
Cramps is another subject well discussed among athletes and electrolytes supplementation has always been advised to prevent cramps. But lately some studies have shown that ingesting something like sour like pickle juice would alleviate the cramp pretty quickly. But how do you define a cramp? There is the cramp cramp where a muscle seizes locally due to overstraining or fatigue of a muscle group. And that is what we are talking about here. But then according to other scientist there is another type of cramp that can occur during long endurance event, you know that kind of achiness felt more generally in the legs? The scientist from the GSSI (again) claims that this type of cramp could be alleviated by sodium intake. Remember that study from Pr Noakes? It showed there was no effect but then was there enough sodium ingested, given the fact that some athlete can lose much more from the chart above. Again there are no specific studies that looked at that. But how many times have I heard that salt was helping an athlete not to get cramp. Maybe it is the placebo effect but maybe there is something to it and scientists should listen to the athletes!
Who is right and who is wrong?
Based on what we know, one thing is sure avoid overdrinking. Clearly 1.2L per hour is too much for most people and one should follow their thirst. You will probably get dehydrated and it is OK. Better than hyponatremia. You can also acclimatize yourself to dehydration and regain some of the lost performance by starting some training sessions slightly dehydrated! Women should also be careful. Hormonal variation especially during the luteinizing phase makes us drink more and we tend to retain more water so thirst might not be the best mechanism. Also as we get more tired, the thirst sensation might get impaired. So maybe drinking to thirst is fine but you should definitely monitor your intake and above 800 ml/hour, you should be watching yourself for symptoms of hyponatremia. This is in agreement with the new ACSM guidelines which recommends 400-800ml/hour but also says that there are no blanket statement as everybody is different. For longer event such as Ironman and Ultrarunning bigger people and heavy sweater in the heat, it is possible that you still could be very thirsty and that 800 ml/hr would not be enough. If you are sweating 2L/hr, 800 ml/hr for a 70kg athlete would make you lose 18% of body weight during an Ironman. Way to much. You are therefore encouraged during training in similar condition as your race to assess your sweat rate by weighing yourself before and after. You might not be able to absorb 2L/hr though but you can try to get closer to this rate if that is your case.
Should you replenish with electrolytes too? Definitely not for shorter events <2-3 hours in mild temperature. But for longer or warmer events, if you are a heavy sodium sweater it would be worth a try to see if this strategy would alleviate some of the achiness later in an event. Practice during training start with 250mg/hour up to 1g/hour and see how you feel. You can also add more salt to your diet the days preceding an event. You should always drink at least 2-3oz of water every time you take in a salt pill such as salt tab which has 240 mg of sodium per tablet. That way it gets easily absorbed and does not end up as a brine sitting in your stomach. If salt is too concentrated, your stomach would have to draw water in before it gets absorbed. Not good. If you are using plain water with that adding a pinch of salt to your water helps with absorption. Carbohydrates are even better at doing that, so you could also add a little sweetness (1tsp or less) to it such as honey or maple syrup (less fructose).
Some products on the market are banking on that already and already contain a mix of carbohydrates and sodium. That is why Osmo for example designed for hydration has a lot of sugar in it, up to 18g/16 oz but only 300 mg of sodium so it is a good thing to be aware of if it is part of your fueling plan. Another similar product is Skratch Lab. Gatorade has even less sodium, higher osmolality and even more sugar. I like SOS rehydrate which has 660 mg of Na per 500 ml, the right osmo and only 6g of sugar plus extra magnesium, definitely a bonus for athlete (and I’m not even sponsored by them). But the best in my mind is the salt tablet as mentioned above because you get total control of what works for you.
If you really want to take the doubt out of this, you can actually get tested to know your sodium sweat rate and basic sweat rate. More and more labs are now offering this. You would then know at which end of the spectrum you are. Although be aware that this is not a fixed value and will vary to a certain degree (heat acclimatization, hormonal status, diet…)
I personally do well with 500mg/hour, but was wondering lately if I should try to go even higher? So I’m going to get tested soon. Stay tuned!