Fiber. It’s not a very…sexy topic. Just the word conjures up images of Metamucil commercials with the sandy-looking granules swirling in a glass and promises of being “regular.” But the benefits of a whole food, high fiber diet are many and certainly extend beyond the water closet.
Most Americans are fiber deficient—some experts in the functional medicine community claim that it’s the most clinically important dietary deficiency, a deficiency largely due to the Standard American Diet (SAD), which doesn’t favor whole, nutrient-dense foods like fruits and vegetables (complex carbs) and is chock full of sugar and processed carbohydrates in the form of “junk flour” (conventional bread, pasta, bagels, etc. (simple carbs)).
Unlike macronutrients (fat, protein, and carbohydrates) that our bodies break down and absorb, dietary fiber (also known as roughage or bulk) isn’t actually digested. It comes in two forms, soluble and insoluble; both are essential and can be obtained from a wide variety of delicious, high-fiber foods like true whole grains (vs. flour), fruits, vegetables, nuts, seeds, and legumes, which indeed, are mostly carbohydrates. (If you’re aghast at the suggestion to consider whole grains and/or legumes, you can read my prior post for Dr. Blum, In Defense of Grains and read my post[JG1] , In Defense of Legumes.)
Because of the common fiber-constipation association (you’re not allowed to laugh if you’ve never had it), many may not be aware of the many other benefits of adequate fiber intake:
- Promotes weight loss: What if I told you that fiber may be your best friend if you’re trying to lose weight? According to Monica Reinagle, licensed nutritionist, “Trying to lose weight on a low-fiber diet is like parallel parking without power steering.” Foods rich in fiber are filling, which means you eat less and stay fuller longer.
- Lowers risk of digestive conditions such as irritable bowel syndrome
- Lowers risk of heart disease by getting rid of digestive debris and environmental toxins and keeping bad cholesterol in check.
- Lowers risk of diabetes: Researchers are now finding that the fiber in grains specifically lowers the risk of diabetes. A September 2018 study from The Journal of Nutrition that followed 55,000 middle-aged women and men for 15 years discovered that those who consumed the most whole grains had the lowest risk of Type 2 diabetes.
- Lowers risk of stroke
- Provides fuel for the microbiome: You may be thinking…What?? I thought I was supposed to be low-carb to heal my gut and reverse my autoimmune condition. Read on!
Low Carb, Low Fiber?
We can’t discuss the important role of fiber and sidestep the carb conversation, given that so many gut-healing, immune modulatory diets eschew—or largely eschew—carbs and that fiber-rich foods are largely carbohydrates.
Fact: A low-carb diet, with its overreliance on fat and protein and under-reliance on complex carbs in the form of whole grains, legumes, and vegetables (including—and especially—starchy vegetables like sweet potatoes, yams, squash, carrots, etc.), tends to be low-fiber.
The importance of fiber in the diet is indisputable and has a profound impact on our digestive health and microbiome, our 100 trillion organism-strong “mini ecosystem” also known as “the forgotten organ.”
Justin Sonnenburg, PhD and Associate Professor of Microbiology and Immunology at Stanford, is the author of The Good Gut, co-authored by his wife, Erica Sonnenburg, PhD. The Sonnenburgs are considered some of today’s preeminent experts on digestive health and in the science of the fibers found in grains and their role in providing an important fuel source for the microbiome.
Justin says, “You have to ask the question of what it means when we’re consuming 15 grams of dietary fiber per day instead of 150—a 10-fold decrease in the foods that feed our gut microbe.”
In their book, The Good Gut, the Sonnenburgs state, “Increasing dietary fiber is essential to cultivating diversity in the microbiota. Microbes in the gut thrive on the complex carbohydrates that dietary fiber is primarily composed of. But rather than ‘dietary fiber,’ we prefer ‘microbiota accessible carbohydrates,’ or MACs. MACs are the components within dietary fiber that gut microbes feed on. Eating more MACs can provide more nourishment to the microbiota, help gut microbes thrive, and improve the diversity of this community. Our family eats what we jokingly refer to as a ‘Big MAC diet.’ This diet is rich in complex carbohydrates from fruit, vegetables, legumes, and unrefined whole grains, and is designed to create and maintain diversity within the gut microbiota.”
Dr. John Douillard states, “While fiber is linked to heart health, it is also critical for the protective health of the intestinal skin. If the intestinal skin breaks down, the beneficial gut microbes disappear.”
If you’re still unconvinced that grains and legumes can be part of a gut healing protocol, Dr. Susan Blum mentions quinoa, amaranth, millet, teff, buckwheat, various types of rice, and legumes in her book, The Immune System Recovery Plan, and incorporates these foods in several of her recipes. She calls them “foods to include” and states, “Fit lots of fiber onto your plate in the form of veggies, low sugar fruit like berries and apples, whole gluten-free grains, and legumes—to feed the good bacteria of the gut.”
It’s Easy to Get Enough
If you think you may be fiber deficient, slow and steady wins the race. Going overboard and increasing your intake with gusto can cause gut distress. And drink plenty of water.
Regardless of any deficiency, we all need regular fiber in our diet. At the end of the day, if you’re committed to a whole foods diet rich in color and variety, you’re likely getting the fiber that you need.
- Add nuts and seeds (especially flaxseeds and chia) to whole grain cereals, salads, soups, and smoothies
- Snack on raw veggies
- Legumes/beans play well with others; use them in soups, salads and many of your other favorite dishes
- Choose true whole grain foods vs. refined grains
- Eat fruit as a dessert or snack; the skin and/or seeds is where you’ll get the most fiber. Berries are a great choice, as they’re low on the glycemic index. Apples and pears are the best skin-on fruits.
- Incorporate all kinds of vegetables into every meal. In general, the darker the veggie, the higher the fiber. Get all that you can—it all counts!