Citrus fruits

Oranges, grapefruits, and mandarins are all rich sources of fiber and a refreshing snack. One orange (about 154 grams) has 3.7 grams of fiber, which is 15% of the RDI. Meanwhile, one grapefruit (approximately 308 grams) has over 5 grams of fiber, which is enough to satisfy 20% of your daily fiber requirements.

Citrus fruits, particularly their peels, are high in the soluble fiber pectin. Pectin can help to speed up colonic transit and relieve constipation. Citrus fruits also contain a flavanol called naringenin, which may contribute to their anti-constipation effects. Naringenin has been found in animal tests to stimulate fluid secretion into the colon, resulting in a laxative effect. However, the further human study is required. Citrus fruits should be eaten raw to receive the most fiber and vitamin C. Oranges and mandarins make great snacks, while grapefruit goes well in salads or as a breakfast sliced in half.