Adults need at least 6 cups of water per day, 8 cups is better. Although various liquids are effective, such as tea, juice and vegetable soup, the best choice is water, with a daily intake of about 2,000 to 3,000 ml. As for the intake of fiber, adults generally take 20-35 grams of dietary fiber per day, and at least 30 grams for constipation patients. Fiber mainly comes from combined carbohydrates, such as cereals, fruits and vegetables. If you choose your food carefully, it is not difficult to get 30 grams of fiber a day. For example, half a cup of green beans provides 5 grams; a small apple provides 3 grams; and a bowl of oat bran provides 13 grams. However, you should gradually increase your fiber intake to avoid excessive gas.