Similar logic might have you arguing that there is no need to change the oil in your car because it is running fine. At present, the typical American diet contains about 12 to 15 grams of dietary fiber per day, which is about half of what we need. Taking a fiber supplement may work for constipation, but supplements’ ability to achieve fiber’s other health benefits is questionable. Whether fruits, vegetables or grains, we want a food that contains the entire package of nutrients as produced by the growing plant. Medications may also be affected, so check with your health professional before adding any fiber supplements to your diet.