Here's an idea: Meat is a better source of potassium than milk or fruits and vegetables (except maybe avocado which is an excellent source). It's funny, the vegetable and milk lobbies seems to have the media's ear on vitamins, anti-oxidants, etc., but the truth is there are some essential vitamins that can only be obtained from meat. And if you eat stable fats (i.e., naturally saturated) you decrease your need for anti-oxidants.

If you are supplementing with salt, as recommended by Atkins, but not with SBD, you are also helping to keep your potassium and magnesium at optimal levels. Magnesium also plays a big role in preventing cramps, which mainstream health advice seldom mentions.

I cannot recommend highly enough Phinney and Volek's The Art and Science of Low Carb Performance. It explores this way of eating from so many angles and will give you a good overall idea of the myriad health benefits. It has a whole section on avoiding cramps. It will also give you a framework into which you can plug all the tidbits gleaned on this website (and others).