Public health guidelines from the US Food and Drug Administration (FDA) advise Americans to eat between 20 and 30 grams of fiber a day, but most adults don't even eat half that much.
This isn't surprising, since fiber refers to the indigestible portion of plant foods, and in the largely refined standard American diet, healthful fibers are often processed right out.
Unless you regularly eat whole fruits and vegetables, nuts, and seeds, you may be missing out on the healthiest forms of fiber available – and that could be a problem. That said, in spite of their fiber content, bulking up your diet with bran muffins and cereal is typically a big mistake, which I'll explain shortly.
Why Is Fiber So Important?
I've long been interested in the health benefits of fiber. In fact, when I was in medical school 33 years ago, I was so convinced of fiber's many benefits that my nickname was Dr. Fiber.
I've since come to appreciate that the type of fiber in your diet, as well as your gut health, play a major role in harnessing fiber's health potential while avoiding its potential pitfalls. Before I explain, let's go over a bit of fiber basics...
It is actually because your body can't digest fiber that it plays such an important part in digestion. Soluble fiber, like that found in cucumbers, blueberries, beans, and nuts, dissolves into a gel-like texture, helping to slow down your digestion. This helps you to feel full longer and is one reason why fiber may help with weight control.
Insoluble fiber, found in foods like dark green leafy vegetables, green beans, celery, and carrots, does not dissolve at all and helps add bulk to your stool. This helps food to move through your digestive tract more quickly for healthy elimination. Many whole foods, especially fruits and vegetables, naturally contain both soluble and insoluble fiber.
There's no shortage of research showing how fiber may boost your health. Some of its top potential benefits include:
Blood sugar control: Soluble fiber may help to slow your body's breakdown of carbohydrates and the absorption of sugar, helping with blood sugar control.
Heart health: An inverse association has been found between fiber intake and heart attack, and research shows that those eating a high-fiber diet have a 40 percent lower risk of heart disease.
Stroke: Researchers have found that for every seven-grams more fiber you consume on a daily basis, your stroke risk is decreased by 7 percent.
Weight loss and management: Fiber supplements have been shown to enhance weight loss among obese people, likely because fiber increases feelings of fullness.
Skin health: Fiber, particularly psyllium husk, may help move yeast and fungus out of your body, preventing them from being excreted through your skin where they could trigger acne or rashes.
Diverticulitis: Dietary fiber (especially insoluble) may reduce your risk of diverticulitis – an inflammation of polyps in your intestine – by 40 percent.
Hemorrhoids: A high-fiber diet may lower your risk of hemorrhoids.
Irritable bowel syndrome (IBS): Fiber may provide some relief from IBS.
Gallstones and kidney stones: A high-fiber diet may reduce the risk of gallstones and kidney stones, likely because of its ability to help regulate blood sugar.
Wait: Read This Before You Stock Up on Bran Muffins!
Bran muffins, whole grains, and cereals are often touted as the best way to increase your fiber intake, but according to a growing number of experts, including Dr. Loren Cordain, a professor at Colorado State University and an expert on Paleolithic lifestyles, humans are NOT designed to eat grains, and doing so may actually be damaging to your gut.
Dr. Cordain explains:
"There's no human requirement for grains. That's the problem with the USDA recommendations. They think we're hardwired as a species to eat grains. You can get by just fine and meet every single nutrient requirement that humans have without eating grains. And grains are absolutely poor sources of vitamins and minerals compared to fruits and vegetables and meat and fish."
But the problem isn't only that there are superior sources of nutrients; grains actually contain anti-nutrients that may damage your health. Ironically, since we're often told that whole grains are one of the best sources of fiber for our health, the high-fiber bran portion of grain – a key part that makes it a whole grain—actually contains many of the anti-nutrients.
Substances in grains, including gliadin and lectins, may increase intestinal permeability or leaky gut syndrome. Leaky gut can cause digestive symptoms such as bloating, gas, and abdominal cramps, as well as cause or contribute to many others symptoms such as fatigue, skin rashes, joint pain, allergies, psychological symptoms, autism, and more. All grains contain glutinous proteins known as prolamines that can be very "binding," as they are pasty substances our bodies were just not designed to breakdown correctly. Plus, while fiber may be good for blood sugar, grains are not and may worsen health conditions like diabetes.
There's even research showing that too much fiber may increase your risk of conditions like diverticulosis, i.e. intestinal polyps. It's a vicious cycle, too, because once your digestive tract has been damaged, it allows various gut contents to flood into your bloodstream where they wreak havoc on your health. Further, if you eat a high-fiber diet with a damaged gut, it can lead to serious problems.
If Your Gut Isn't Healthy, a Temporary Very-Low-Fiber Diet May Help
If you have chronic digestive symptoms like diarrhea, flatulence, stomach pains, reflux, leaky gut syndrome, food allergies, or intolerance, you'd be wise to implement the GAPS program. GAPS stands for Gut and Psychology Syndrome. It also stands for Gut and Physiology Syndrome. The first part of the GAPS Introduction Diet is to remove fiber because it feeds microbes.
The human digestive system is not designed to break down fiber. Instead, it ends up undigested in your bowel, where the majority of your gut flora resides. If your gut flora is healthy, i.e. dominated by beneficial, probiotic species, then these microbes will feed on the fiber and proliferate.
However, if your gut is filled with pathogenic bacteria and/or yeast and fungi, fiber will actually make your symptoms worse, as it is a non-specific growth factor for intestinal bacteria, and does not discriminate between pathogenic and beneficial bacteria. So, if your bowel is predominantly dominated by pathogenic microbes, pathogenic microbes will feed on fiber and proliferate, making whatever health problems you have worse.
The digestive system of those with GAPS is predominantly populated by pathogens, which is why fiber must be carefully eliminated from your diet, for a period of time, to help starve out the pathogens (probiotic-rich fermented vegetables and soups with well-cooked, deseeded and peeled vegetables, such as zucchinis and squash, are allowed in the introductory phase). If you're interested in trying this out, I highly recommend getting Dr. Natasha Campbell-McBride's book Gut and Psychology Syndrome, which provides all the necessary details for the protocol.
What Are the Healthiest Sources of Fiber?
Assuming your gut is generally healthy, I believe most people need upwards of 50 grams of fiber per 1,000 calories consumed. Most Americans get nowhere near this amount. As the New York Times reported:
"...the current average fiber intake in the United States is about 13 grams a day for women and 17 for men. Increasing these amounts by seven grams a day would bring them close to the recommended levels of 21 to 25 grams for women and 30 to 38 for men. 'Seven grams a day increase is an achievable goal...' 'You're talking about... increasing vegetable and fruit by two portions a day.'"
If your diet could use more fiber, resist the urge to fortify it with whole grains. Instead, focus on eating more vegetables, nuts, and seeds. The following whole foods, for example, contain high levels of soluble and insoluble fiber.
Chia seeds Berries Vegetables such as broccoli and Brussels sprouts
Root vegetables and tubers, including onions and sweet potatoes Almonds Psyllium seed husk, flax, and chia seeds
Green beans Cauliflower Beans
A simple "rule" to remember is simply to get most of your fiber in the form of vegetables, not grains.