Did you know that we benefit from parts of food we can’t digest? Most people know that we should eat more plant foods: fruits, vegetables, grains, beans, seeds and nuts. Beyond hosting a rainbow of vitamins and minerals, foods growing from the soil and trees provide a major source of fiber, which plays a crucial role in maintaining our overall health and wellbeing even though our bodies aren’t able to break it down. Getting enough fiber can be tricky sometimes, but it doesn’t have to be! Read on to learn more about this special component of plant-based foods and how you can incorporate more of it into your diet for better health.
What is Fiber?
Fiber is found in plant foods like vegetables, fruits, legumes, grains, nuts and seeds. Dietary fibers are carbohydrates in foods that human bodies lack the ability to digest or absorb, but that does not mean they are useless! Depending on how it interacts with water, dietary fiber is categorized as either soluble or insoluble. Both forms of fiber provide gastrointestinal benefit.
Why is Fiber Important?
Soluble fiber forms a gel-like substance in water, and picks up bile salts, molecules that help us digest and absorb fat, on its way through our digestive system. To make more bile, the body must break down cholesterol. Making bile reduces the total amount of cholesterol circulating in blood vessels, and thereby potentially decreases cardiovascular disease risk. Oats are a good source of soluble fiber and are often associated with heart health for this reason.
Insoluble fiber, unlike soluble fiber, does not dissolve in water. It passes through the digestive tract quickly, adds bulk to the stool and prevents constipation. This is important because regular bowel movements are crucial for maintaining a thriving and diverse population of bacteria in the gut.
Why should we care about keeping our gut bacteria happy and diverse?
Most recent estimates show that there are just about as many cells in our bodies as bacteria. That’s upwards of 3.7 billion bacterial cells that have the potential to influence our health in some way.
Scientists are only beginning to scratch the surface of the benefits associated with gut bacteria. It seems that different strains provide different benefits, and we can influence the amount of good bacteria by feeding them the right kinds of food (that is, dietary fibers).
Adequate intake of fiber has been associated with a healthy gastrointestinal tract, reduced risk of cancer, heart disease and diabetes, a more resilient immune system, appetite management and better weight control.
Most studies look at overall dietary patterns and their relationship to health and disease. It shouldn’t come as a surprise that people who eat the most fruits, vegetables, whole grains and legumes have the best health!
What Are Prebiotics?
You may have heard of probiotics - beneficial bacteria that can be consumed either as a supplement or in fermented foods like sauerkraut and kombucha. It is thought that by consuming these beneficial bacteria in our diet, we can populate our digestive tract with the “good guys” and benefit from all the health-promoting action they provide. But these bacteria need to eat to survive. Dietary fibers nourish the good guys, and keep bad bugs on their way out.
Not just any dietary fibers will do. Prebiotics are a subset of fibers that are fermented by gut bacteria, and stimulate their growth and abundance. While not all fibers are prebiotic, beneficial bacteria generally need these types of fibers to thrive. Prebiotic fibers specifically are found in foods like leeks, asparagus, chicory (inulin), Jerusalem artichokes, garlic, onions, wheat, oats and soybeans (among many others).
Though prebiotic fibers provide benefits by feeding gut bacteria, the byproducts of their fermentation include gas that certain individuals may be particularly sensitive to. Some experience gastrointestinal (GI) distress with even small amounts of fermentable fibers in the diet. This can be addressed by working with a Registered Dietitian to identify the type and dose of fibers responsible for the most severe symptoms, and build a balanced diet that does not contain the identified FODMAP (fermentable oligo, di- and monosaccharides and polyols - fermentable prebiotics) in an amount that causes GI distress.
Where is fiber found?
You can find fiber naturally in most plant foods, such as vegetables, fruits, grains, and legumes. Seeds are also a great source, especially when consumed with the shell intact. Oats are famous for their cholesterol-lowering effect thanks to the particular makeup of soluble beta-glucan fibers in the grain.
Fiber can also be added to processed foods in isolation to boost its fiber content on the nutrition facts panel. This is why you might see “high fiber” cottage cheese or yogurt (as an animal product, cheese and yogurt do not contain dietary fiber) in the grocery store. Typically, inulin, or chicory root fiber, is added to these foods, which as an isolated fiber has been associated with poor tolerance in some people.
Though specially-formulated high-fiber products may boost the total fiber in your diet, it is still not clear whether fiber alone is the only reason high-fiber diets are associated with the best health. For instance, fiber is found in plant foods that also provide a host of antioxidants and other plant compounds that could supplement or work with the fibers and provide even greater health benefits.
Do people get enough?
The recommended amount of dietary fiber per day is that which has been associated with the greatest reduction in cardiovascular disease risk. Per 1,000 Calories, adults and children should aim to consume 14g of dietary fiber. For an average 2,000 Calorie diet, the recommended amount of fiber is 28g per day.
According to the most recent dietary guidelines advisory committee report only 4% of men and 13% of women consume this amount every day. How can anyone add more fiber to their diets? Eat more whole grains, beans, cruciferous vegetables like broccoli and kale, fruits, nuts and seeds. For those following a gluten-free diet, getting the recommended amount of dietary fiber every day can be especially challenging, as many gluten-free grain products are made with refined flours that have the fibers removed. For gluten-free fiber, look to legumes like beans, gluten-free whole grains like buckwheat, amaranth and quinoa, and products made with seeds, garbanzo or other bean flours.
When increasing the amount of fiber in your diet, remember to also drink more water. Water and fiber work together to prevent unnecessary discomfort as it passes through the digestive tract.