Fiber is the part of a plant that the body can’t digest, meaning it’s not absorbed into the bloodstream. Of the two types of fiber—insoluble (does not dissolve in water) and soluble (dissolves in water)—soluble deserves a big chunk of credit for helping the heart. Diets low in saturated fat and cholesterol, and rich in fruits, vegetables, and grain products that contain some type of dietary fiber, particularly soluble fiber, may reduce the risk of heart disease. Viscous soluble fibers (a kind of soluble fiber found in oats and barley) can help lower total and LDL cholesterol. Although the mechanisms for how they do so are not fully known, they seem to benefit heart health by lowering these cholesterol levels. Insoluble fiber has also been associated with decreased risk of cardiovascular disease in high-risk individuals.  Many plant-based foods contain varying degrees of both types of dietary fiber, but you’ll find higher levels of fiber in foods like oats, ready-to-eat whole grain cereals, peas, beans, carrots, and citrus fruits, to name a few. One type of soluble fiber found in oats and barley, called beta-glucan, has been shown to be particularly helpful in lowering levels of LDL cholesterol. Insoluble fiber is abundant in wheat-based cereals, whole wheat breads, apples and cauliflower. (Check out these easy ways to sneak more fiber into your day.) But helping to manage cholesterol isn’t the only way fiber benefits your heart health. You can also thank fiber’s filling characteristic for helping to protect your ticker, as eating a high-fiber food can help fill you up (and make you less likely to hit the doughnuts later). Here’s where other fiber properties kick in: Some types of fiber bind with water in the stomach so you may feel full enough to say no to seconds. And because it takes longer to move through the stomach, eating fiber also means you may be less likely to crave something higher in fat or cholesterol later on (see ya, doughnuts!).  The Daily Value for fiber for all Americans is 25 grams per day based on a 2,000 calorie diet. But estimates show that most adults are consuming only about half of that. To help get your daily fiber fill, do some advance planning and aim to get a third of your needs in each meal, plus a snack or two.  More from Prevention: High-Energy Foods To Keep You Going Strong