Marathon Swimming Nutrition: Do it yourself

The last in a series of four posts about nutrition in marathon swimming. To recap:

  • Marathon swimming nutrition is both art and science. There are both “best practices” (generalizable to many) and “special sauce” (generalizable to few). In general, a nutrition plan that aims to drink some carbs — not too much is a good place to start.
  • Some carbohydrates are “better” than others, due to differences in osmolality. An endurance athlete can consume more carbohydrate in the form of maltodextrin, compared to simple sugars, without overwhelming the digestive system. Also, maltodextrin is neutral in taste, thus providing more control over your drink’s flavor.
  • Of the many designer endurance fuels on the market, few are ideal for marathon swimming. High electrolyte content makes sense for runners, cyclists, and triathletes – but less sense for swimmers (even less sense for ocean swimmers).

Although I do think Perpetuem is a good product for swimmers, my best advice is to skip the one-size-fits all formulas and do it yourself. This is the only way to ensure you get the nutrition you need on a marathon swim, and not the stuff you don’t need.

There are two basic varieties of “DIY,” the “full DIY” and the “semi DIY.”

The Full DIY

  1. bulk maltodextrinBuy some plain complex carbohydrate – maltodextrin (Carbo-ProMaxim, or bulk) or if you want to be adventurous, Superstarch.
  2. Mix your chosen carb with water, and flavor it with something tasty. Possibilities might include fruit juice or Gatorade.
  3. Calculate your drink recipe by:
    1. how many calories (including the ones in your flavoring) you want to consume per hour
    2. how much fluid you want to consume per hour
  4. If you’ll be swimming in warm water and/or freshwater, add some electrolytes (e.g., Hammer Endurolytes). Keep in mind many fruit juices already provide some potassium.
  5. If you want to add some amino acids, go for it (try this).

This is, in fact, exactly what I do. For a 30-oz feed bottle, I mix:

  • 1/2 cup maltodextrin (bulk for everyday use; Carbo-Pro or Maxim for race day)
  • 6 oz fruit juice – anything but citrus. On my big swims last year I used unfiltered apple juice. But other juices work great too – cranberry (unsweetened), blueberry, cherry, pomegranate, grape, etc. You can even blend them!
  • 24 oz water

This recipe provides approximately 280 calories and 70g carbohydrates (depending on the juice). Assuming bulk maltodextrin ($33.54 per 12 lbs) and premium juice ($4 per quart), the total cost of my 30-oz custom bottle comes to $1.06. For everyday workouts, I dilute the recipe by 50%, bringing my cost down to 53 cents.

Important Caveat: Some people have trouble digesting fructose. Fruit juice contains fructose (along with glucose & some other stuff).

Always test your feed plan before you use it on a marathon swim!

The nutrition info for Maxim and Carbo-Pro are pretty boring, but here they are anyway:

Maxim Energy Mix

Maxim Energy Mix

  • carb source: maltodextrin only
  • extras: Vitamins C and B1
  • cost per 250ml: $0.32

Carbo Pro

Carbo Pro

  • carb source: maltodextrin only
  • extras: none
  • cost per 250ml: $0.45

The Semi DIY

  1. Infinit NutritionGo to the Infinit Nutrition website.
  2. Complete the online interview (or schedule a phone consultation).
  3. Get your customized formula. Infinit will blend it, put it in a nice little bag, and mail it to you.

Everything is adjustable – flavor, calories, electrolytes, protein, amino acids, and even caffeine. Tell them what you want, and that’s what you’ll get. You could even have different formulas for different swims – perhaps a low-electrolyte formula for a cold ocean swim, and a medium-electrolyte formula for a warm lake swim.

(No, I’m not getting anything for saying this. However, my buddy Jared – who initially brought Infinit to my attention – is sponsored by them.)

24 thoughts on “Marathon Swimming Nutrition: Do it yourself”

  1. Now if only one could show data supporting the use of carnitine for endurance sports… (for the record, I don’t think supplementation works) – but it would be nice if it did.

    1. You don’t think supplementation in general works? Even amino acids? For most fad supplements, you’re probably right. There does seem to be some intriguing data on choline… see Donal’s post.

  2. I meant I don’t think supplementing marathon feeds with carnitine increase fat metabolism. Some supplements are beneficial.

  3. In your 2011 Tampa Bay Marathon Swim you drank a similar Maxim mixture (176 cal, 44g carb). How many ounces of this drink did you take per hour? And, does your marathon DIY regaime still include a protein drink? This insight on nutrition is great. It couldn’t come at a better time for me. Thanks!

    1. Chris,

      In Tampa last year, I drank approximately 10oz per feed, feeding every 20 minutes. Within each 1-hour cycle, I had two Maxim feeds and one Perpetuem feed. Perpetuem provided a welcome change of flavor, in addition to some protein. Including protein in your feed plan is a personal choice. I don’t think it’s necessary, but in theory it reduces muscle wear & tear, and also hunger.

          1. I switched from Perpetuem to Accelerade but am not real fond of that either. I’m going to stick with the Maxim for the entire swim. Great info!

  4. Evan,
    As someone transitioning from ultrarunning to marathon swimming b/c of a total hip replacement, I’ve found your nutrition series to be quite interesting. The crossover on fueling and other aspects is direct. Your comment about swimmers not needing as many electrolytes caught my eye. Is your general assumption that cool/cold water = less “sweating”? Or, is the assumption that even in warm water, a swimmer’s body generates less perspiration and thus replacing electrolytes is not as critical as it is for someone running 100km, for example?

    1. Hi Luke. I have a total hip replacement, too! 6 years & still going strong. I’m glad to have someone here with experience in other endurance sports… I’m very interested in the parallels (and contrasts).

      Here’s the thought process on electrolyte loss in swimming:
      – In general, people sweat less in water than on land, because it’s not functional for temperature regulation. To be clear, people DO sweat in water – just not as much.
      – Swimmers sweat more in warm water than cold water – but even in warm water, probably less than running.
      – In the ocean, swimmers are constantly ingesting sodium (via saltwater) – more than enough to replace what is lost through perspiration.
      – More relevant to swimmers is potassium replacement. This is one of the reasons I use fruit juice as my flavoring.

      Thank you for commenting!

      1. Take a cup of warm coffee (80 degrees C) and put it in a cool room (10 degrees C). Take an identical cup of warm coffee and place it in a filled sink of water at 10 degrees C. The cup submerged in liquid will cool MUCH faster. Solid to air contact transfers heat MUCH slower than solid to liquid contact. Therefore a swimmer heat is dissipated easier while swimming than running. As a result perspiration is not required to the same degree to cool off.

  5. Good post. Additional consideration: duration of swim.

    I think we talked before about how for some people, (I’m one) maltodextrin can overload the kidney’s ability to continually process. EC pilot’s are so familiar with this that they start to expect it after 10 hours. And indeed I was one of those, at 11 hours, out of the blue, (in the blue?), I had to throw up … Felt much better after and functioned perfectly. Having done 8 & 9 hour swims previously, the problem hadn’t arisen. It is also possible that it is partly due to the extended prone position.

    Second, as part of that, many of the guys here take a break from carbs one feed every 3rd or 4th hour (I’d have to check my plan) where it’s have an electrolyte only, for the same reason as above.

    1. Is that specific to maltodextrin? I would think any type of carb has the potential for overload. Perhaps consuming fewer calories/hour in the first 10 hours would make the post-10hr symptoms less likely to manifest. I still can’t imagine how Lisa C. managed 600 cal/hr for a double, or whatever she did….

      1. It can’t be specific to maltodextrin. Kidneys filter blood. The only carbohydrate within the blood is glucose. If it were really true, it would mean one would need to cut back on the feed size. I would think that the kidneys would hurt more from increased blood flow from exercise leading to increased filtering and dehydration. Also, during a channel swim, increased electrolytes are a huge burden on the kidneys. As far as macromolecules, carbs are generally safe on the kidneys, while increased amounts of proteins are more problematic.

        1. Great stuff, Sully. Lots to “digest” here, haha. It would seem to make sense that if people commonly get sick in the E.C. after 10 hours, then cutting back slightly on the feed size in the first 10 hours would prevent it.

          1. Yeah, not maltodextrin exclusively just forget to clarify since that’s only what we use.

            Lisa is one to the ones who doesn’t seem to have the overload problem and she has a very clear understanding of when she takes the carb breaks. At least not for 36 hours anyway so far!

    1. When I wrote that I guess I still harbored a vague superstition that the higher-priced Carbo Pro or Maxim were somehow higher quality than the bulk stuff. I don’t anymore – they are nutritionally identical. Only advantage is that quick-dissolving (QD) malto, which is used in Carbo Pro & Maxim, dissolves quicker than the bulk ‘Carbo Gain’ brand malto. In case you’re in a hurry, or something.

  6. Hi – for your full DIY – any idea by how much you would decrease that for a woman or would it be more or less the same?

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