The component of the diet that feeds the unhelpful bacteria that can accumulate in the small intestine is starch. Starchy foods, as we all know, are high-carb foods that our bodies can turn into glucose for use as fuel. Not every kind of starch, however, is completely digested.
Starch comes in two main forms, amylose and amylopectin. Both kinds of starch are really just collections of glucose molecules, which serve as stored energy for the plant. A single molecule of amylopectin can consist of up to 2 million molecules of glucose. A chain of 25 to 30 molecules of glucose will connect to two or three more chains of 25 to 30 molecules of glucose until there is a molecular “blob” of sugar waiting to be digested. Our bodies break down this kind of starch easily.
Amylose, on the other hand, consists of just a few hundred to a few thousand tightly packed molecules of glucose, configured in a way that digestive enzymes have a hard time penetrating the molecule. This form of starch tends to resist digestion, that is, it is a “resistant starch,” and becomes food for the kinds of bacteria that release gas.
Corn, beans, and potatoes can contain up to 70% amylose, the hard-to-digest starch. Sticky rice and waxy barley can contain up to 100% amylopectin, the easy-to-digest starch. If you are on a strict paleo diet, you won't be eating corn, beans, potatoes, rice, or barley, but if you choose to stray from your diet, and you have GERD, you will have a lot less trouble with heartburn and stomach acid if you avoid the corn, beans, and potatoes and you choose sticky rice or barley.
If you just have to have your potatoes, choose Russett, Desiree, or Pontiac potatoes. They have the least amylose of all the major varieties of potatoes. If you have to have your rice, choose jasmine rice or sushi rice and avoid basmati rice. White bread will cause fewer problems that whole grain or whole-meal bread. Bagels are especially likely to cause fermentation and gas.
Need to indulge in dairy? Make sure it's lactose-free (not just treated with Lactaid). Even better, drink almond milk. If you eat grains or starchy vegetables, eat them hot. Don't eat them cold. Cold starchy vegetables contain greater amounts of gelatin-like, resistant starch.
If you are going to drink alcohol, avoid mixed drinks, dessert wines, sweet wines, and any kind of beer other than light beer. Drink light beer, dry wines, and distilled liquor in moderation, if at all.
As for your choices on a standard paleo diet:
- Edamame usually don't aggravate GERD. Almost all other beans, peas, and legumes do.
- Miso soup doesn't trigger fermentation. Almost any other noodle, lentil, rice, or tomato soup will.
- Parsnips, yams, plantains, sweet potatoes, fresh lychee fruit, fresh mango, ripe bananas, green bananas, raisins, and prunes tend to aggravate GERD.
- Plain yogurt is OK as long as it is not sweetened with sugar alcohols (see below), but yogurt sweetened with fruit is a no-no.
- Almost no food is more likely to cause acid reflux than sugar-free ice cream.