The Electrolyte Debate: What to drink during your marathon?

I’ve previously dabbled in the alchemy of finding the magic elixir of running. Look for a future post on my weird marathon carb-loading regimen (I use the Western Australian method). I’ll also probably write one about what to eat on race morning, so I am excluding those subjects from this post.

I have fought to push GU down during my previous 4 marathons. I just can’t seem to stomach it at race pace, although I don’t have nearly the problems others note. This, coupled with a recent depletion run bonk, caused me to rethink what I should intake during a race.

There is a significant debate out there over hydration, electrolytes, and calories during a run. Disclaimer: I am not a doctor, and I don’t even play one on tv. So, take all this with a grain of salt (or don’t, more on that in a minute).

I am not going to plow any new ground here. I’ll lay out the basics, give you my conclusions, and pose a few questions along the way. I’m interested in what works for all of you though – what have you tried?

My main sources for my conclusions here are “Advanced Marathoning” and “The Paleo Diet for Athletes.” There are 3 components in this equation: 1) how much fluid?; 2) how many calories?; and 3) electrolytes – yes/no/which/how much? (obviously the muddiest issue).

#1 – Virtually everyone agrees that you need to take in some fluid during the race. Except maybe Alberto Salazar. Elites will dehydrate themselves to a certain degree during a race, but there is a point at which this becomes counterproductive. Studies show that a certain amount of dehydration does not decrease performance. You can also drink too much during a race – especially if you’re out there for a long time and are drinking only water: this condition is called hyponatremia, and it can be just as deadly as dehydration – it’s just not as well-publicized. Exactly how much fluid you need depends on your sweat rate – which varies based on the environment and you. You lose 3-4 pounds of water during a marathon on a hot day, 2-3 on a cool one. Also, your stomach can only empty so much fluid per hour. It looks to me like average consumption should be around 24-28 fluid oz. per hour. Conclusion: I’m shooting for 6 oz. every 15 min.

#2 – My two main sources agree on the amount of calories you should intake during a race – basically 200-300 per hour. Conclusion: for 3 hours out there, I’m targeting 700+ calories.

#3 – Electrolytes. Sodium is the biggie. AM says you need it – recommending a ratio of 250mg/L. AM specifically recommends it to avoid hyponatremia and improve caloric uptake. The Paleos don’t agree as to its benefit – but waffle on the conclusion. To be fair, I think what they are saying is that it really doesn’t help as much as we think, although on balance it seems to recommend it. Also, I think I see a flaw in their reasoning. Basically the theory is that the sodium content of your sweat is less than in your body, thus sodium becomes more concentrated in your body as you exercise and sweat so you don’t need to replace it. But…(and I didn’t go to the source study so maybe they just skipped a step) if you’re sweating out sodium and other electrolytes and drinking straight water (or something with calories and no electrolytes) during a race, that should dilute the concentration of sodium in your body, right? Duh? The Paleos admit there’s no known downside to taking in sodium during a race and may be a slight advantage – improving the rate of absorption of water and carbs – thus ultimately concurring with AM. That’s enough for me. Conclusion: a dash of salt. The AM ratio is designed to not exceed the level of palatability. I have seen other formulas with 5-6x the sodium. I tried one. It’s barely drinkable. The new Gatorade Endurance formulation boasts 3x the sodium and 2x the potassium of regular Gatorade. However, it doesn’t have sufficient calories in my estimation – 80 per 12 oz – only 480 if you drink 72 oz. It also has a lot more sodium in those 72 oz. – 1740 mg – than the AM formula would recommend (532 mg). Plus, I can make this stuff way cheaper than a $30 canister of powder, and without any food coloring. I’m going to split the difference between Gatorade Endurance and AM: 1120 mg/72 oz.

On to potassium. AM and the Paleos are silent on the subject, but Gatorade includes it in their formulation. PDA does discuss it in the context of cramp prevention – but says available studies show no benefit. PDA does recommend it as part of recovery. Anecdotally, whenever I had a huge calf cramp after 2-a-day soccer practices in HS I’d make sure I had a banana or two that night. I eat a lot of bananas these days, which seems to ward off the cramps for most purposes, however I have experienced significant calf cramping in 2 of my 4 marathons. Also, one of my other sources – a Doctor/runner who passed along the World Health Organization’s Oral Rehydration Solution (“ORS” – for treating severe dehydration) includes potassium as an ingredient, but again in a fairly high concentration. Since I am not planning on suffering a bout of explosive diarrhea before the race, I’m going to compromise with a lower concentration closer to the Gatorade number of 840 mg potassium: 795 mg/72 oz.

There are other electrolytes to consider, but I am not adding them to the witches brew at this time, primarily magnesium. Spinach and pumpkin seeds have a lot by the way. So does swiss chard.

The recipe:

72 oz. of marathon electrolyte/fuel/fluid (that’s a lousy recipe name. Maybe MEFF72? Sounds vaguely Victor Conte-ish. Maybe I should go register that with the PTO).

  • 1 cup of dextrose
  • 1/2 tsp. sea salt
  • 1/4 tsp. Nu Salt
  • 1/2 cup lime juice (or to taste)
  • water to fill to 72 oz.

Notes: 1 tsp of dextrose has 15 cal. There are 48 tsp. in a cup. So 1 cup of dextrose is 720 calories. Dextrose aka glucose is used because it is a simple sugar – a monosaccharide – rapid absorption. It’s also more easily tolerated than fructose. Sucrose is an ok substitute, but it’s a disaccharide, so there’s a metabolic process there. You can get dextrose at a brew shop or Amazon. Sea salt is sodium chloride, obviously. 1/2 tsp. yields 560 mg of sodium. Nu Salt is potassium chloride. It’s sold just about everywhere as a salt substitute. There are alternatives, but watch out for Lite Salt that also contains sodium – then you’re doubling up. I’d really prefer 1/6 of a tsp., but who has that measuring spoon. 1/4 tsp. yields 795 mg of potassium. If that sounds like a lot, you need a lot more K per day than you do Na. A banana has over 500 mg. So I’m not worried about OD’ing on K. Lime juice is purely for flavor. I like Nellie & Joe’s Famous Key West Lime Juice. It’s the next best thing to fresh.

Using the recipe:

I am going to be such a wannabe at the Heart of America marathon. I’m going to split these 72 oz into 6-12oz. bottles and have the RHSW place them at aid stations for me. The advantages of a small race! Run like the elites! I’m going to try to pick one up every half hour and drink 1/2 right away, the other 1/2 15 minutes later. I’ll start the first bottle pre-gun.

I’ve tried it out once already and tolerated it well. I think it will be easier than GU to get down. I was a bit nauseous in the first few miles of the Garmin marathon. AM tells me that’s because I’m pushing harder than I should at the beginning. Well, that’s how I race. I can race a bit better than my training would predict, but not without a price.

As with any “new” thing – try it before you race it. If you try it, let me know what you think!


One comment on “The Electrolyte Debate: What to drink during your marathon?

  1. […] on course formulation, not a pre-load. I have my own recipe for that in a previous post (here: MEFF72) but in order to achieve the higher concentration of sugar, you’d have to use the powdered […]

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