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Why Does A Guy Like Lance Armstrong Have Gastrointestinal Issues During A Triathlon?

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Last week, at Ironman 70.3 Galveston, Lance Armstrong decimated the field on the bike, but then slipped to a disappointing seventh place finish due to hydration and nutrition problems during the run.

So why does a guy like Lance Armstrong have gastrointestinal issues during a triathlon?

And what should you be eating during a triathlon?

In today’s interview with Dr. Stacy Sims, you’ll find out what to eat during a triathlon, and also learn fascinating new information about fueling that is going to change many of the recommendations that I personally make, and the way that I eat and drink during Ironman.

Dr. Stacy Sims is an Innovative Exercise Physiologist, and a Nutrition Scientist of Thermoregulation, Hydration, and Performance Nutrition, and also involved with “Kai Nutrition“. She is an accomplished athlete in her own right, having ridden as an elite women’s cyclist, won multiple Xterra events, and even raced as a pro triathlete. Her cutting edge research with athletes has led her to work with the likes of Garmin, RadioShack and Lance Armstrong where she has helped athletes of all abilities find the extra edge through science.

During my discussion with Stacy, I ask her:

How common are GI problems among runners and endurance athletes, in terms of rough percentages of athletes who have some kind of GI distress during a race?

What is going on physiologically during intense exercise or dehydration that can cause gut issues? 

Can use of any supplements or medications aggravate this issue even more?

Does exercise, and specifically a form of exercise like running, cause changes in your gut muscles or the way your intestines work?

Are these type of GI issues more prevalent in men or women, and if so, why?

What are the most common mistakes athletes make in terms of race day meal planning, and are there specific compounds (lactose, fructose, etc.) that should be avoided?

What do you think is the best carbohydrate fuel during exercise, and why? 

Do you think there are any issues with gels and if so, are there better solutions, like blocs, chomps or jelly beans?

What about sucralose and other artificial sweeteners?

There are a variety of concentrated sport drinks on courses, such as Powerbar Performance, Gatorade, etc. Are these OK to drink?

Do you think that endurance athletes should be using electrolytes, or would you agree more with the philosophy of Tim Noakes that the body does a pretty good job maintaining plasma sodium levels? If we do use electrolytes, are certain forms better than others?

Any final tips that can be using in a pinch to stop GI issues? 

So what were some of my biggest takeaways and changes that I will personally make in Half and Full Ironman triathlons, based on this discussion?

1) During races, begin using green tea extract, delta-E, or 5 hour energy – rather than coffee or caffeine tablets.

2) During the run, switch a sucrose or glucose based solution, and avoid fructose/maltodextrin sources. I’m doing more research on this right now, because here are the current gel options on the market (notice that Clif uses “brown rice syrup” which is basically sucrose).

Gel ingredients

3) If I do use any Powerbar Perform or GU Brew drinks during an event, dissolve 3 parts water to 1 part solution.

4)  Include 10-20g protein prior to races, or better yet, use a pre-digested aminos source such as MAP capsules

5) Avoid any electrolyte capsules or solutions that use chloride, and instead opt for carbonate, along with a trace minerals solution consumed during week of race and before race.

6) Keep Peppermint Tums on hand during run.

Questions, comments or feedback? Leave them below.

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69 Responses to “Why Does A Guy Like Lance Armstrong Have Gastrointestinal Issues During A Triathlon?”

  1. Kelcey says:

    This was one of the best podcasts ever, Ben. Thanks! Wish I could get a recipe for an energy drink to make at home, maybe with honey or coconut water??

    • There are a lot of recipes out there, Kelcey.

      For example, you can take 32oz of liquid like coconut water or plain water, add 1/8-1/4 teaspoon of Himalayan sea salt, 1/4-1/2 tsp calcium magnesium powder or crushed tablets, 1/4 cup of juice (lemon, lime, grape, apple, etc), and 1 tsp sweetener (honey, etc.).

      I personally don't really use energy drinks at all, although you'll often find me swigging coconut water….

  2. Stacy says:

    ah.. RE gels- you've forgotten about the concentrated carbohydrate in a dehydrated gut aspect– need plenty of fluid to minimize GI problems!

    • Yes, I plan on focusing more (when/if I do keep using gels) on dosing with water throughout. I never get GI issues, but for me, I'm looking at this more from a heat production standpoint.

    • Amy says:

      Ben and Stacy, amazing podcast! My drive to LA went by in a flash listening to this. I've sent many tri friends to listen in. My question for you guys is if you can elaborate on artificial sugars and bloating… not only performance implications but in general everyday consumption.

      • Stacy says:

        Hi- sugar alcohols (xylitol, sorbitol, mannitol), and sucralose have sweetness but not "digestible" carb. So it is the nature of the breakdown of the compounds and the body not being able to completely absorb the residual molecules that contributes to bloating and gassiness. Everyday consumption in limited aspect is fine for these listed above. But stevia is a much better option as sugar alternative- it is a dried plant leaf.
        Hope this helps.

  3. Caig says:

    Great podcast! I looked through what Amazon had to offer and settled on Botanic Choice Liquid Extract, Green Tea. This one looked pretty good to me. Ben, what do you think?

    Also, I sent a note to Infinit Nutrition. Maltodextrin is the first ingredient (at least in my formula) but they do include Sucrose. I asked them if they could swapy the Malto with Glucose. I'll let you know what they say.

    • Keep me posted on what Infinit says, Craig. That green tea extract looks fine to me, although it might not transport real well during a race, which is why I'm going to stick to delta-E personally…

  4. Kem Johnson says:

    Interesting podcast. Stacy doesn't like fat for fuel, it appears.

    • Yes, but it is a bit of an issue if you want to do Ironman triathlon (or even a Half) and do it FAST. That means you're up around 80-95% carbohydrate utilization the whole time, liver and muscles get glycogen depleted after about two hours, and both beta-oxidation and gluconeogenesis are too slow. Fat doesn't work as a fuel at those intensities.

      That's why endurance sports like this are bad for you if you want to go fast. You have to eat a bunch of telomere shortening carbs.

      But boy, are they fun. ;)

  5. Ioan Rees says:

    Please, is there any way you can do a "Part 2 interview" to ascertain Stacey's opinion on nutrition through T2 and on the IM run? You touched on GI distress being potentially exacerbated by physical jolting on the run, but did not delve into run specific hydration and nutrition solutions.

    This would be very helpful for me ( as well as all your IM listeners I'm sure). I'd be intrigued to hear how her "hydration in a bottle, calories in the pocket" strategy for the bike translates to the run context.

    • Perhaps Stacy will reply, but I would suspect that her T2 recommendations won't be much different than what she recommend on this podcast (and what she recommended on this podcast would be the type of thing you'd want to do on the IM run – careful with high gel doses and try to stick to sucrose/glucose, esp. at higher intensities).

      • Stacy says:

        Hey all-
        Yes, T2 onwards is quite different from the first 2/3 of an IM race. Happy to chat or write a bit more.
        Stac

        • Dr Ioan Rees says:

          Stacy. Could you tell us how you'd fuel & hydrate from T2 through the IM marathon (following on from your bike recommendations)? Many thanks. Ioan

          • Stacy says:

            Hi Ioan-
            There is a different need from T2 to the end of the marathon- The biggest thing(s) are minimizing stress on the body (primarily the GI system and heat load). You're looking at trying to fuel to keep a steady blood sugar and fluid level to allow for a steady power output.
            The following is the general schematic of what my athletes have found to be the most effective and successful means of fueling (provides a negative split to a non powerdecline run)-

            At T2-
            1) a sodium+fluid load- using 2 tablespoons sodium citrate+1x "lite" emergen-C +1 tablespoon table sugar in a 20oz bottle– usually frozen (in the camelbak insulated bottles or even a stainless steel coffee thermos- something to keep it as cold as possible- this helps drop core temp). If you don't want to make your own, then use KaiNutrition Inc's OSMOPreload.
            2) Salty REAL FOOD- my aussies and kiwis like maramite/vegemite on white bread or cheese foccacia- just a few bites to get high GI bread and salty b-vits. Non commonwealthers like cheese+ham sandwich or whitebread with salted jam inbetween.
            3) TUMS!– I have yet to meet any IM athlete that doesn't experience stomach prob the first 2-5 mile of the run- as I mentioned in the podcast, it's the change of position and sudden impact upon the gut that causes a bit of disarray. So chewing 2-4 extra strength tums will help (carry with you on the run as well-)
            4) optional- but icy cold mexican coke

            On the run- I've had a few people who thought they had to stop at every aid station, until we did IIM run-throughs, then they realized that they could do 3-5miles without the aid station, BUT because of the tenacity of the gut- in the pocket had bites of salty bread, tums, and in the other oatmeal or choc chip cookies (the real ones, full of fat and sugar!), then in the bottle they carry diluted electrolyte- at aid stations, topping up with coke and water.
            1/3 of the way through the run, some use S-Caps, (I don't recommend electrolyte or salt tabs at all- anything concentrated into the gut at this point can be a bad idea; besides if you are eating salty foods, drinking electrolyte and water, preloaded at T2 (and the week leading up to the race with magnesium, salt, potassium), then you shouldn't need electrolyte/ salt tabs at all! ) and most throw back 1/2 5-hr energy or some green tea extract.
            2/3 way through- another shot of caffeine
            last 1/3 of the run- this is where it can be dicy– if you've been on the real food, electrolyte, coke aspect, you may find you just want a few bites of something different at the aid stations- potato chips/pretzels, cookie, –but DO NOT hit the engineered nutrition at this point– will be too much for the stomach with regards to the straight carb.
            What we have found is glucose tablets or a 3-4 jellybeans/swedish fish/other sucrose based easy to chew/swallow candy every ~5-10 min works to keep the blood sugar constant, doesn't overload the gut and allows even poweroutput.
            Fluid across the board should be the same- you're own mix in the bottle, at special needs- another ice cold sodium+fluid load or just icy drink- and then coke, water at aid stations.

            Like I said, this is the general schematic, so you'll have to tailor it to your own body. The biggest take ways are trying to stay away from engineered nutrition, and eating small bites along the way.

            Stacy

          • Ioan, this is good that you're getting this information…please remember that what we provide on the podcast is free, so for personal consulting, you may want to consider actually hiring the doctor or myself to help you!

  6. Horacio Lyon says:

    Hi Ben, now im really puzzled what to eat! Im doing very vertical & long trail 84k next Sat and I have already bought 25 Rocktanes, 5 generation ucan packages (cornstarch)[yes I know you dont seem to like them] and maybe its better not to use them at all…
    I personally think its a kind of difficult to fuel 60 grs/hour or carbs only with sucrose and glucose products… Even honey has a lot of fructose! What can eat for fueling now!! buaaaaaa :( Help!

    • Horacio…first of all, take a very deep breath! There is no one "perfect" way to fuel. Most important thing I've found is not to mix a bunch of fuels together. For example, what you've described is fructose and maltodextrin from Roctanes combined with even higher molecular weight starches from UCAN. Just too much stuff.

      Here's the deal: ultrarunning is low intensity. I'd go with Superstarch (the UCAN stuff) combined with medium chain triglycerides or coconut oil along with some amino acids like Master Amino Pattern if I were in your shoes. That is what I would do. Listen to next Friday's podcast for more info, but basically, I would not be doing a bunch of high carb Roctanes for a lower intensity event like an 84K run…

  7. What about Generation UCAN product? Stacy? Ben?
    http://generationucan.com/aboutus.html

    • I'm going to discuss those in Friday's podcast, but basically: A) have the issue with high heat generated upon oxidation but B) good option for training sessions where you're only eating 50-100 calories of carbohydrates and primarily relying on fatty acid utilization, especially if you're going for ketogenesis/low insulin.

      • Thanks for the info, I found 2 weeks ago, that I have a hard time of burning fats…versus carbs during training or maybe something else was going on (there was has been a change in my workouts from morning to evening too)…but I started eating 75g or so of carbs at night (with same training intensity,,mostly aerobic with 2 days of "speed") the following week my energy levels were back to normal…not sure I do so well in ketogenic state or perhaps I wasn't as balanced as I should have been (carb, protein, fat) or my body just isn't acclimitized to those things yet (ketosis)…working on it though…

  8. Dr Nicole Anderson says:

    Hi, just came across this excellent interview. I recently totally rehauled my race nutrition and had a very nice IM Melbourne PB marathon on a background of recovering from coeliac disease over past couple of years. In summary, with fairly obsessive food diary and weight measures I did notice hormonal effects on weight (obviously relating to female cycles) and decided that a month before the race to avoid all dairy and unfermented soy products for this reason. Also being magnesium deficient as a result of coeliac disease, I (unfortunately) have found that I can allay virtually all abdo, resp and mood problems with daily magnesium intake of 300-900mg depending on my training load. For very long training (up to 10hr ride across Tasmania, and the 4 day Wildside MTB race) I also used diluted GuBrew with 300mg (just an arbitrary dose – 1 scoop, nothing scientific!) MetaMag (Ethical Nutrients/Endura) added per 750ml bidon. I found with bricks after using magnesium in the sports drink, I did not have any of the GIT problems I usually have suffered in the past. Testing this at IM Melb (was a cold race), I had dilute Gubrew + metamag in 750mls twice on the bike, 2 bananas on the bike, SIS Go gel (maltodextrin only) to 50gCHO/hr, and saltstick 1 cap per hour. I was able to run off the bike at a much higher cadence and did not get any GIT issues until very late in the race during the hill efforts, and I had been using Torq (Maltodextrin/Fructose) mainly because of its awesome flavours. I will try reducing the maltodextrin/fructose and changing electrolyte to avoid chloride as much as possible and see if there is the possibility of racing Busselton (usually a hot IM) with even less GI upset. Thanks so much for this very good advice.
    The problem will be sourcing a gel which is not maltodextrin – Cliff shot gels do contain maltodextrin – the blocs don't, however I don't fancy chewing while running. I might experiment with making my own gels – we use glucose syrup with diabetic emergencies and it seems to give a good shot of energy quick enough to wake the (nearly) dead!

    • Solid! Thanks for the info, Dr. Anderson. I noticed you use magnesium on a daily basis because of the celiac disease, and I'm curious what source you use for that (liquid vs. powder vs. transdermal).

  9. Dr Nicole Anderson says:

    Further to my previous post, one burning question I have is the role of oral glucose absorption, and the action of amylase on maltodextrin breakdown to its simpler sugars and whether this is a feasible way of glucose absorption. I am aware of some studies showing performance benefits with a "swish and spit" of carbohydrate fluid registering increased glucose levels in lab (usually 40km TT) conditions. I have previously used a method of holding gel (SIS Go gel and TORQ) in my mouth for as long as possible then rinse w water and spit out when feeling queasy. Seemed to work in that N=1 experiment. Is there any info on oral absorption of maltodextrin?

    Re the magnesium – its magnesium diglycinate 3g per serve making about 300mg apparently bioavailable magnesium – to be honest I chose this to mix in my drink because it tasted the best! I have tried a more B vitamin heavy mag powder however it does have the aftertaste which is not nice regurgitating when in aero! Blackmores do a BioMag tablet which I have taken when I don't have my drink powder with me, which is good for conference travel etc. I am a big fan however of the epsom salt bath (cheap, easily accessible) post heavy workouts. Much nicer than an ice bath. And perhaps there is also that nice mild euphoria after too, which I identify as a magnesium effect on mood. I have been previously a bit skeptical of the transdermal absorption (our skin is pretty good at keeping things out too), however I wonder if someone is deficient, then I guess there would be a homeostatic pull via the transdermal route if the nutrient was on offer, I'm not sure of the cellular mechanics to achieve this tho.

    • Dr. Anderson, regarding question 1, we actually discussed this on a previous podcast. There is a very small amount of oral glucose absorption. If I recall properly, it came out to around 15-20 calories per hour. The ergogenic aid of swish and spit was primarily neural.

      Thanks for the info on the magnesium. If you choose to use magnesium flakes rather than epsom salts you can vastly improved absorption, but, as you mention more expensive and harder to get.

      Dr. Marc Sircus has a very good book on Transdermal Magnesium that goes into how it is absorbed: http://www.amazon.com/gp/product/1450283543/ref=a

  10. jeff Hoening says:

    Great show, Ben, with sound advice. Our own self-experimentation trumps all in my opinion. Try all kinds of fueling options and you'll know when you've hit your nutritional "clutch point".

  11. erin says:

    Awesome interview! Will have to listen a second time to get all the great info. I like the simplicity of "hydration in the bottle and fuel in the pocket", but as a marathoner I have a hard time with chewing while running, so have always mixed my hydration and fuel together with a homemade carb-rich sports drink or pre-mixed Gu/water solution. Three questions: 1) Any recommendations for fructose- and maltodextrin-free fueling products that don't require chewing? 2) if the goal is to hydrate with a 3% solution, wouldn't frequent fueling with small amounts of food (to avoid a large solute load in gut) make the solute concentration in the gut less than ideal for hydration, and in essence the same as a sports drink that's aiming to provide fuel and hydration in one? 3) and, I understand the recommendation to avoid fructose (b/c the liver conversion step produces extra heat), but what is the issue with maltodextrin? Thanks for the great content!!

    • 1) Erin, look in Clif gels, and I'll keep folks posted on other solutions; 2) technically yes, which is why you need to experiment with any solids that you are planning on using during the race, and why I personally only use solids on the bike; 3) maltodextrin, the issue is that it is a large/longer chain molecule.

      Again, bear in mind we're talking about high intensity exercise here, not lower intensity, aerobic fat burning stuff.

      • Nadine says:

        What about Carbo-Pro. It is comprised of glucose polymers from corn, barley and rice and has low osmosibility. I find it is the only carb source that I can take in for 6+ hours. Sometimes I mix it with vitamin water (just plain sucrose).
        Nadine

  12. Craig Huggart says:

    I product I use has Glucose and Sucrose. However, they also include maltodextrine . They say they do it because it is very difficult to get the amount of calories you need without the malto. What do you think?

    • stacy says:

      What calories do you need?? The addition of maltodextrin is to maximize carbohydrate calories without impacting osmolality as much as fructose does. BUT the key behind fluid intake should be HYDRATION not calories. Glucose+sucrose+ sodium gives maximum fluid absorption; a nuance from the carbohydrate supplementation that standard liquid calories are pushing.

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  14. get.sladed says:

    Fascinating interview that turns things I thought were valid upside down. Ben, you did a great job covering a huge amount of information in a short amount of time. Correct me if I'm wrong but this information is most applicable to a "hot" distance event.

    Unlike what was said in the interview, NUUN does not appear to have sucralose but it does have sorbitol. Does that make it an issue then anyway? It also has carbonates and bicarbonates.

    There was frequent reference to not ingesting fructose. Can we assume this is referring to extracted fructose and not fructose that comes from real fruit? (e.g. she said her pre-workout meal included berries.)

    She said Powerbar/Ironman Perform was "ok" but it lists the carb blend as maltodextrin, fructose, and dextrose. Maybe I'm dense but this confuses me if it's 1st 2 sugars are "not recommended".

    • NUUN does have acesulfame potassium, which I avoid as a potential neurotoxin, and I prefer their uHydration product for that reason (http://www.nuun.com/what_is_nuun/nutrition_and_ingredients/)

      Concentrated fructose was the main focus of that statement, not fruit, so the answer to that question is yes – mostly we're just talking about engineered nutrition that has concentrated fructose. So in something like Powerbar Perform, you're watering it down by 2/3, so it's less of an issue. I personally do not plan on using an "liquid nutrition", although if I personally did, I'd go for CarboPro.

  15. janet says:

    Ben, which would you prefer before a race delta E or energy 28? What are the difference in ingrediunts in both? I would like to use before marathon's. Great podcast , listened to it twice . Enjoy them all. thanks for sharing.
    also if you would share specific brands of what to 'eat ' during a marathon not to cause GI issues.
    thanks

    • Honestly, I use both. The ingredients are different, as Energy28 is more stress control and delta-E is more focus. If I had to choose one or the other, I'd go with delta for short races and Energy28 for longer ones.

      As far as brands of what to eat, I have a discussion going on right now on my private athlete forum about this. Basically, just stick to what Stacy talks about, looking for brands with Sucrose, Glucose, etc. Clif gel, Accel gel, stuff like that…

  16. Chris says:

    I am confused by Dr Sims statement that fructose/maltodestrin blends create a thermoregulation concern that sucrose does not. She states that while sucrose does contain fructose, the metabolism of fructose in the presence of glucose does not create the heat issue because glucose acts as a cofactor in the metabolism of fructose such that the extra heat isn't generated. However, the body breaks down maltodextrin quickly into glucose (has a GI similar to glucose); so a fructose/maltodextrin blend would end up with a fructose and glucose combination. So why would this be any worse than a fuel that contains glucose and sucrose?

  17. Derek says:

    At last years IMWI I made my own energy drink and it worked well for me. I thought I would share it because I think it would fit into Dr. Sims recommendations, albeit higher on the grams of carb's than she suggests. I mixed one clear bottle for the bike that included 2000 calories (20 scoops) of Carbo-Pro. Not the kind with the added aminos, just straight glucose. This stuff dissolves very easily so you can mix it strong. I added in my own aminos. I use BASE aminos, 5 scoops. I drew lines on the bottle so I could monitor my caloric intake shooting for 400 an hour, and drank free water as needed. I supplimented this with a 100 calorie ground up oat bar my wife makes each hour. For the run I mixed up 4 fuel belt grenades of the same solution, carrying 2, and picking up 2 more at special needs. The temps were in the mid 80's at the start of the run, and my gut handled it nicely.

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  19. Jeff says:

    I've been a big fan of GU and GU roctane with straight water. I use 1/2 pack of blocks only in Ironman distances every hour on the bike. I never have GI distress. If it isn't broke why fix it. I think Ben uses this kind of protocol also. It seems to work for me well as long as I drink when I'm thirsty. Maybe I'll switch from GU gels on the run and use something like Cliff shots to see it this keeps my energy levels up on the run.

  20. Just remember…Clif doesn't have amino acids like Roctane does, so you want to add in some BCAA capsules or something like Master Amino Pattern…

  21. Jeris says:

    A couple of points that are worth mentioning in light of a few comments about fat burning for IM distance races, as well as the idea that the body fuels "80%-95% carbohydrate utilization" (especially if we run ironman "FAST"), which is not really accurate.

    First off…Ironman (or most any effort over a hour or so in duration) is going to be an aerobic effort. You guys are all talking like this is an anaerobic event. It's not! The body can't maintain an anaerobic state for that long. Even if you could have sufficient fuel intake (carbs) to replace fuel expended (which you can't — just do the math), the rest of your body (including your muscles) would not tolerate that level of exertion for that period of time. No one races an Ironman or a marathon anaerobically…and no one can. Those who try end up walking the run, if they make it that far, and/or experience failure due to GI distress, "bonk", or other physiological problems related to trying to give an anaerobic effort for an event that requires aerobic function.

    I won't go into how one should develop the aerobic system. That's a different matter that is often lost in the "training de jour" of high intensity anaerobic methodology that has come and gone from time to time over the last 60 years or so. But for sake of brevity, TI muscle cells use primarily fat as an energy source. TII use primarily glucose. (There is also TIIb fiber types) Anaerobic = glucose utilization = TII fibers. Aerobic = fat utilization = TI fibers. Aerobic activitiy does require some glucose, as it's required for the conversion of fats. Also, aerobic vs. anaerobic is a continuum. There isn't a switch that turns one fiber type off and the other on. They're both used in an event. The key is which one is used predominantly.

    TI is our endurance, TII is our "fast" and explosive, but fatigue very quickly. I'm reminded of the cycling adage of burning matches. You only have so many anaerobic efforts in your legs in a race and when you fatigue those TII muscles, they're pretty much gone. The idea is to save your matches for when you need them cause they're limited!

    This is basic exercise physiology. I'm not saying we don't need the glucose or need to fuel with it in a race, because we do. Nor am I saying we need to fuel with fat. Although some do, I personally haven't tried. The point I'm trying to make is that there seems to be confusion on the fuel our body needs and uses during endurance efforts. Make no mistake. Your body only carries a finite about of carb fuel. You can only ingest a certain about of carb fuel during a race. The amount you ingest will never approach the actual amount of fuel you actually use during the race. Don't try. Wanna save some of the trouble of all this and avoid trying to micro-manage your in-race fueling? Train your aerobic system and it will do what it does best…use onboard fat as fuel…and you'll get faster at more aerobic efforts. The further up the continuum into anaerobic efforts we go, the more we create potential for GI distress as the body draws blood and fluids away from the stomach and gut to support the more anaerobic effort. This isn't a difficult issue. It's not rocket science.

    Finally…I agree with one of the posters above who said don't fix it if it's not broke! If you're nutrition is working for you, don't monkey with it. There'll always be another study around the corner to enlighten us on why we're not doing the right thing, why something new is better, or why the "old school" way actually was the best way, or or whatever. Don't chase every rabbit that runs by. If it works for you, leave it be. Unless you're experiencing GI issues, bonking, dehydration, etc (and you know it if you are!) your in-race nutrition will not make you faster. Training will make you faster.

    • Good points Jeris.

      Having worked in an exercise physiology lab for several years (and I do have an upcoming article in LAVA magazine about this), I can attest to the fact that at Ironman intensities (typically 85-95% of lactate threshold heart rate), carbohydrate utilization can reach up to 700 calories per hour (and that's just the component of calorie utilization derived from carbohydrates).

      This is why loss of glycogen and limited blood sugar can severely hamper performance in Ironman even though compared to, say, a 400m track sprint, Ironman is an aerobic event.

      • Jeris says:

        Carbohydrate utilization of 700 calories per hour would be a maximum, I think. Most endurance athletes are able to metabolize around 500 calories in carbohydrates per hour. Either way, most people cannot ingest and absorb carbohydates at a sufficient rate to replace that which is lost. As you know, Ben, 1g carbohydrate = 4 calories. I hate to reference studies because there's a study to prove or disprove virtually anything…and to make matters worse, so many are poorly done to the point of making them nearly useless for practical use. But the preponderance of evidence suggests maximal carbohydrate absorbtion during cycling to be about 90g per hour, and running to be about 60g per hour. Also, specific application to Ironman racing shows that taking in 20%-30% less than maximal results in optimal performance for most people, if they can handle that much. (As an aside, it's been shown that elite marathon runners seldom exceed 40g-50g carbohydrates per hour…that's 160g-200g)

        But for the sake of arguement, let's assume one does have the capacity to ingest and absorb a full 90g per hour. That's only 360 calories. A far cry from the 500 burned…and nearly half of the 700 you mention. Conventional wisdom holds that 60g (240 calories) is about the top end, notwithstanding some of the mixed glucose studies cited by some of the engineered supplement manufacturers. Point being, we're trying to fill a bucket with huge holes in it, losing more than is being put in. Most people can't do it.

        This sort of ties into my whole point. Endurance is primarily an aerobic activity. The more anaerobic we try to make it, the more difficult it is to fuel for it. I personally believe these nutrition issues, including much of the GI distress and bonking, are largely a non-issue for those who train and race properly…at least it's much less of an issue. Not that it's NOT important, but that there's much more room for error rather than trying to walk the razor with less than optimal training and racing methodology.

        As far as the composition of the carbs we ingest during a race…I'm sure you've read the Jeukendrup studies, among others. But that's a whole different angle…for another time. :-)

        • When Jeukendrup worked with Chrissie Wellington she was pushing over 500 calories of carbohydrate per hour ingested on the bike. I average about 450 calories per hour during Ironman on the bike, and I'm extremely metabolically efficient from a fat burning standpoint. A marathon is a very far cry from an Ironman because it *barely* dips into complete liver and muscle glycogen depletion.

          Lab values rarely are appropriate once you toss an athlete into a race, but if you listen to the really fast athletes talk post-race, many are literally at 100-110% VO2 max power for a good 15-20 30-60 second surges during the Ironman bike. That is extremely anaerobic.

          But if somebody just wants to "baseline" for Ironman and stay at lactate threshold minus 15-20 beats, lower carb intake and lower overall calorie intake is fine if they've trained to be metabolically efficient…

  22. Jeris says:

    The usual disclaimer applies: The reason elites (you included!) are elite is because they have physiological attributes and/or genetics rest of us don't. :-) I'll restate: MOST people can't metabolize much more than 500g carbs per hour, much less ingest 500g per hour. I didn't (and still don't) really think that was debatable.

    Regarding Chrissie Wellington, in her own words: "In half and full iron-distance races, I take on one gram of carbs per kilo of body weight per hour. The carbs are a mix of sugars (glucose and fructose to increase glycogen absorption). In an Ironman, I have two bottles (430 calories in each) on the bike, plus two gels and a chocolate bar. I make my first drinks bottle slightly less concentrated than the second, to make it more palatable early in the race (especially if I’ve swallowed some open water!). Following the formula above, on the run I have one gel every 25mins – washed down with water." This is the reality of what Chrissie does in an actual Ironman race and it falls right in line with the recognized norms and limits for the bulk of humanity that I cited earlier. I suppose if Chrissie could effectively ingest and metabolize 500g carbs per hour during an Ironman she'd probably do it.

    How many cumulative minutes do you propose an athlete…even an elite…is able go extremely anaerobic, say 100%+ VO2Max, during an Ironman? How many minutes do the Type II muscle fibers have in them at that level of effort before they become toast for the remainder of the race? I can give you the clinical answer…what do you suppose is the real-world answer based upon your experience?

    P.S. In case anyone wonders, there are many citations for the Chrissie Wellington raceday nutrition practices. She's revealed her nutrition many times in interviews and on her website. It's always been the same formula as often as I've seen it.

    • I'm basing Chrissie's intake off of what Asker Jeukendrup presented at the Ironman Medical Conference in 2010.

      I would say cumulative anaerobic minutes are probably close to 60 minutes, that's about the most I've personally ever been able to pull off.

  23. Rich says:

    I'm not sure I could stomach a sandwich immediately before the marathon.
    Is it possible that "heavy" foods can create GI distress? Or is it because they need more fluid to digest and as you said, the body draws it from itself.
    I'm a bit confused there, I can handle solids on the bike, up to about 1hr before the run, then its liquids all the way.

    For records sake, I use gu on the run, and I'd say I drink the 8oz of water with it.

    • I agree on the sandwich part, unless she means 2-3 hours prior. Depends on your definition of "heavy" foods – if high molecular weight starches, possibly, especially with longer term use (5+ hours). Even if you have fluid with those, they can still "backup" after awhile.

      I'm same as you: mix of gels/solids on bikes, then gels on run, and never had GI distress.

      • Stacy says:

        Sandwich = white bread, something salty in the middle (marmite, vegemite, salted jam) and just a few bites! not an entire sandwich and not anything full of fiber

  24. Art says:

    Great interview. Thank you. She is very good and I will implement.

    Constructive criticism for her public speaking: She starts majority of her sentences with "so."

  25. Brennan says:

    1) Accelerade drink has a sucrose base but I am assuming the protein included would take away the GI benefits associated with a sucrose base… thoughts? Any thoughts on the 4:1 Carb protein ratio in general during races/training? I plan to experiment but I am curious about general thoughts.
    2) Also… did anyone read the June edition of bicycling magazine that mentioned that there are benefits to consuming multiple types of carbs because your body can only digest so much of each type but mixing can increase the total amount of carbs your body can digest in an hour. I think that portion my have been mentioned by the head Gatorade scientist though…
    Thank you!

    • 1) 4:1 Carb:Protein ratio is more for recovery. Just having some Amino Acids or BCAA's in the gel or taken separately in capsule form is better. Those are predigested and go straight to bloodstream.

      2) True about carb blends. Gatorade and most other gels base their formulas off that kind of research, which has been around for about a decade or so. Issue regarding jiving that w/ Stacy Sims advice is that the two different kind of carbs used are typically a short chain (her recommendation) with a long chain (higher heat of oxidation with long chain). So if you have GI distress with gels, probably not best solution. Otherwise, good way to go.

      • Ben – I didn't see your thoughts about this question: Accelerade drink has a sucrose base but I am assuming the protein included would take away the GI benefits associated with a sucrose base… thoughts?

        I use accelerade but in 1/2 diluted.
        Thanks
        Michelle

  26. Brennan says:

    Hey Ben. Just thought I would share with the group. I just stumbled on this drink from Skratch Labs: INGREDIENTS: sucrose, glucose, sodium citrate, potassium citrate, calcium citrate, magnesium citrate, freeze dried fruit, citric acid, ascorbic acid (vitamin C) http://www.skratchlabs.com/collections/all
    I am going to give it a try.

  27. guest says:

    Informative podcast – it would have been nice for Stacey to acknowledge that she is part of a company that sales these products. She also has Lance Armstrong listed as someone she has worked with – but he still had the gastro problems??

  28. guest says:

    Dr. Sims mentioned Mojo and Luna bars but she said without nuts/fruit – they seem (especially) Mojo to all have nuts? Any recommendations?

  29. Matt says:

    Quick question regarding prerace//preworkout meals. In the podcast Stacy says she premixes almond milk with muesli and tops it off with Whey Isolate. What are your thoughts on using a 1-2% fat greek yogurt instead of the almond milk to get protein and not topping it off with the isolate?

    • Totally depends. For example, I'm pretty sensitive to dairy and it doesn't work well for me. I personally recommend just a couple sweet potatoes or yams with some sea salt or honey pre race. those burn really clean…

  30. johnlewis90 says:

    This is definitely a health relevant article. This will definitely create some awareness among all those athletes who suffer constantly from various intestinal issues. I will continue looking over your blog for more such updates.

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