Soy is a legume! It's a bean = GAS! Soymilk gives me gas about 2 hours after drinking it.
Most foods that contain carbohydrates can cause gas. By contrast, fats and proteins cause little gas (although certain proteins may intensify the odor of gas).
The sugars that cause gas are raffinose, lactose, fructose, and sorbitol.
• Raffinose — Beans contain large amounts of this complex sugar. Smaller amounts are found in cabbage, Brussels sprouts, broccoli, asparagus, other vegetables, and whole grains.
• Lactose — Lactose is the natural sugar in milk. It is also found in milk products, such as cheese and ice cream, and processed foods, such as bread, cereal, and salad dressing. Many people, have low levels of the enzyme lactase needed to digest lactose. Also, as people age, their enzyme levels decrease. As a result, over time people may experience increasing amounts of gas after eating food containing lactose.
• Fructose — Fructose is naturally present in onions, artichokes, pears, and wheat. It is also used as a sweetener in some soft drinks and fruit drinks.
• Sorbitol — Sorbitol is a sugar found naturally in fruits, including apples, pears, peaches, and prunes. It is also used as an artificial sweetener in many dietetic foods and sugarfree candies and gums.
Most starches, including potatoes, corn, noodles, and wheat, produce gas as they are broken down in the large intestine. Rice is the only starch that does not cause gas.
Many foods contain soluble and insoluble fiber. Soluble fiber dissolves easily in water and takes on a soft, gel-like texture in the intestines. Found in oat bran, beans, barley, nuts, seeds, lentils, peas, and most fruits, soluble fiber is not broken down until it reaches the large intestine where digestion causes gas.
Insoluble fiber, on the other hand, passes essentially unchanged through the intestines and produces little gas. Wheat bran, whole grains, and some vegetables contain this kind of fiber.