Most/many of the popular endurance drinks also contain calcium - mostly it is combined in the salt used. Calcium and migraine have a strong link, and a lot of calcium definitely triggers migraines for me. For this reason - Michael/InfiniT has used a different salt supply in my mix to prevent the extra calcium.

I don't know about its effect on the GI tract, but just wanted you to know that you're probably also getting it in your drink mix.

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Elivis needs boats.

I don't know about calcium causing GI issues, but maybe if taken without any Vitamin D it might not be digested/absorbed. I routinely take Calcet tablets, one every ~20 miles on the bike and every ~3.5 miles on the run. They have 300mg of Calcium and 200IU of Vit D each. I've never run into GI issues except when dehydrated *OR* when taking the following drinks:
1st Endurance E3, Endurox R4, Accelerade.

All of these have really really high amounts of Magnesium. Think Philips Milk of Magnesia. 500mg or more of magnesium can cause GI, and 2 servings of Endurox gives you 480mg!!! The body absolutely can't absorb that much magnesium that fast.

Anyway, it is unlikely that calcium caused it, as calcium carbonate in moderate doses is used as an antacid (TUMS). If you want to try something else for the tablets you could consider Thermotabs (450mg sodium chloride and 15mg potassium) or Saltstick caps (550mg sodium chloride, 63mg K, 11mg Magnesium, 22mg Calcium and 100IU Vit D). As a salty sweater myself I typically take 2 Thermotabs, 4 Endurolytes, 2 or 3 Calcets and a couple of K-factors on a 56 miler. I'm experimenting with the SaltStick caps now though, hoping to simplify my nutrition.

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Magnesium inihibits calcium absorption in the body, and it always stymies me to see that a large number of calcium supplements are contain magnesium and zinc. WTF?

Also, the body regulates magnesium very efficiently - but too much of it will result in watery poops - which is a dehydrating process - not exactly what we're looking for in endurance endeavors.

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Elivis needs boats.

That's actually why I like the Calcets. Not only do they dissolve relatively quick, but they are physically small and only have 300mg...compared to a lot of the horse pills out there with 1000mg that your body can't possibly digest. I started taking them because I was having issues with cramping and generalized muscle aches.

Another issue that could cause GI is taking too much salt without enough water. I forgot about this one, but essentially you are throwing too much salt in and your body tries to suck out the water from your stomach. This concentrates stomach acid a lot and can cause problems too.

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Any electrolytes, taken in quantity, will give GI distress (aka, the liquid shits). I've had the same problems during training: take too little and cramp, take too much and end up holding the squirts in.

Calcium in particular makes me dump more than any other electrolyte.

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Mike R

Software Engineer and Mac geek
Aspiring to be front-middle-of-the-pack in 2010.