Bananas contain a large amount of ellagic acid, which has a strong astringent effect and can cause constipation by caking stools into dry and hard stools. In daily life, many people believe that eating bananas can play a laxative role, so some people with constipation will often eat bananas. However, bananas for some people not only can not solve constipation, but also caused constipation. No wonder constipated patients often wonder: why the more you eat bananas, the more you can not solve the stool? The reason is that bananas do not play the role of laxative. As we all know, when the banana is not ripe, the outer skin is green, peel off the outer skin, astringent can not swallow. When ripe, the astringent taste of bananas is swept away and they are soft and sweet, which are loved by children and the elderly. Bananas are tropical and subtropical fruits. In order to facilitate preservation and transportation, when picking bananas, you cannot wait until they are ripe, but have to pick them into storage when their skins are green. The bananas we eat in the north are ripe only after ripening. The astringent taste of raw bananas comes from the large amount of tannic acid contained in bananas. When bananas are ripe, although they no longer taste astringent, the tannic acid content is still present. Ellagic acid has a very strong astringent effect, which can crystallize feces into dry and hard stools, thus causing constipation. The most typical thing is that after the elderly and children have eaten bananas, instead of helping to laxative, they can have obvious constipation. There are many foods that can play a laxative role, such as apples, sweet potatoes, corn and other coarse grains. Apples are rich in dietary fiber – pectin, so apples can play a two-way regulatory role in the laxative problem. When the stool is constipated, eating more apples can play a laxative role. The pectin in apples can absorb 2.5 times more water than its own volume, making the stool soft and easy to discharge, which can relieve constipation. When the stool is diarrhea, the pectin in apples can absorb the water in the stool and thicken the stool, thus playing the role of anti-diarrhea. This “two-way regulation” of apples is very gentle, especially for the elderly and infants. In addition, sweet potatoes, corn, oats, buckwheat and other coarse grains are rich in dietary fiber, also has the effect of preventing constipation.