In the health, wellness, and fitness community, we often hear all about the macronutrients (fat, protein, and carbohydrates). Yet, a nutrient that’s incredibly beneficial to our health is far less mentioned. That’s fiber.
Fiber is best known to keep you regular or prevent constipation, but there are many more benefits. In the athletic community, the one that comes to mind first is helping to relieve that ‘hungry all the time’ feeling that often comes with heavier training loads. Next is gut health, lowering disease risk, and helping to regulate the body’s use of sugars.
Dietary fiber consists of the non-digestible carbohydrates from components of plants. The human body does not make the types of enzymes needed to break the bonds in these fibers, so they pass through relatively intact.
Fiber is found in most plant foods, primarily vegetables and whole grains, as well as nuts, seeds, and fruit. There are two types of fiber— soluble and insoluble. Both are beneficial to our health.
Soluble fiber absorbs water and turns into a gel-like consistency that slows down digestion. Ever had chia pudding or chia in a smoothie and felt full and satisfied for hours? That’s the soluble fiber at work.
Soluble fiber also helps slows the absorption of sugar into the bloodstream so blood sugar levels remain more stable. Food sources include chia, psyllium, flax and other seeds and nuts, oats and oat bran, lentils, peas, and some fruits and vegetables.
Insoluble fiber is not digested by the body. It is helpful for clearing out the buildup of undigested food and environmental and metabolic toxins in the digestive system as it moves through. Insoluble fiber also helps get the digestive system moving and eliminate any constipation. (Side note: constipation is not just having difficulty having a bowel movement. That’s the extreme. It also refers to spending more than just a couple minutes on the toilet, passing hard, dry, small pieces, failing to eliminate daily, and transit time beyond 12-24 hours.) Now that we’ve got that cleared up, insoluble fiber can be found in whole grains such as oats, millet, quinoa, sorghum, amaranth, brown rice, farro wheat, beans, and fruits and vegetables.
Fiber Nourishes Your Gut
Your digestive system is home to trillions of beneficial bacteria, called the gut microbiome. They live in an (ideally) symbiotic relationship with you. This means you and they both benefit from them being there. Just like you, the microbes need to eat to live and grow, so they obtain nourishment from the food you eat. In the case of beneficial bacteria, they feed on the undigested part of the food, (fiber), that is passing through your large intestine by fermenting it into short chain fatty acids such as Butyrate.
A healthy gut microbiome can protect you against disease-causing bacteria because the good bacteria compete for space in the intestines, literally out-populating the bad bugs from taking hold. It can also help you absorb otherwise non-absorbable nutrients like certain antioxidant polyphenols, produce some micronutrients like vitamin K, and provide needed fuel for the cells in the colon. Production of short chain fatty acids by bacteria in the intestine plays an important role in the maintenance of the intestinal barrier. What’s more, Butyrate has also been shown to be protective against colon cancer.
Whereas we don’t want an overgrowth of bad bacteria, having ample and diverse beneficial bacteria is a hallmark for optimal health. Low beneficial bacteria can impact your protective mucus lining in the intestinal tract, which supports up to 80% of our immunity. The commonly used phrase “leaky gut” comes into play here when the interplay between a low fiber diet, low beneficial bacteria count, and difficult to digest macromolecules poke holes in the cheesecloth-like fragility of the intestinal lining and then opens the way for the immune system to do its job –in overdrive – resulting in sensitivities, intolerances, and allergies to many foods that are in your normal routine. Prolonged problems here are part of the pathophysiology of autoimmune diseases.
Fiber Keeps You Feeling Full Longer – Read this again during your next heavy training cycle!
Because fiber is so difficult for your body to break down, it stays in your gastrointestinal tract longer compared to simple carbohydrates like table sugar. Having food in your system helps you feel full longer. This is partly why eating an apple is better than 100% apple juice (stripped of fiber), which is then better than apple-flavored juice (stripped of all nutrients). We even have studies showing that diets rich in high-fiber whole foods help reduce the perception of hunger. This is good information if you experience the “hungry all the time” feeling during heavy training cycles when you’re actually eating enough.
How much do we need?
Research has found that hunter-gathers ate a large quantity of fiber compared to modern humans, upwards of 100g of fiber per day. The average American has around 10-15g per day, and the US Dietary Reference Intake is around 25-38g of dietary fiber per day – which is well above that of the average person –but easily achieved by gradually increasing plant-foods in the daily routine. Can we consume too much? Yes, that is possible. Too much fiber can lead to a bowel obstruction and diarrhea (which is also caused by many other factors).
Some therapeutic diets eliminate fiber-rich carbohydrates temporarily with the aim of improving long-term health and shifting the microbial population. For example, this is the purpose of the low FODMAP diet for small intestine bacterial overgrowth (SIBO), and the candida protocol. Individuals who try an extreme low-carbohydrate or ketogenic diet also do so with the intention of improving health –often by way of improving the body’s response to sugars. But what’s commonly left out of the conversation is that all of these diets are meant to be temporary, because they all come with long-term negative health consequences such as eliminating all those beneficial bacteria that feed on fiber.
One more thing, we often hear the advice to reduce fiber in the days before a big athletic race, or eat ‘quick sugars’ in the few hours before athletic activity. This advice largely depends on the person, since just like we can train our bodies, we can also train our gut. Some of my best marathons were run after eating my routine high-fiber dinner and breakfast. I’ll delve more into this topic soon! 😊
Summary: Dietary fiber is an essential nutrient required for proper digestion of foods, proper functioning of the digestive tract, and for helping you feel full. A deficiency of fiber can lead to constipation, hemorrhoids, and elevated levels of cholesterol and sugar in the blood. Conversely, an excess of fiber can lead to a bowel obstruction and diarrhea. Individuals who increase their intake of fiber should do so gradually since this internal adjustment is going to adjust the populations of beneficial (and not so beneficial) microbial species in the lower GI –and thus might initially come with uncomfortable symptoms.
Now that we’ve got our daily dose of nutrition wisdom, let’s eat! William labeled me the queen of grain salads the other night after presenting this dish. It’s a seasonal variation on a plethora of other fiber rich tabbouleh-like grain salads in the recipe archives of this space –and one I’m really favoring right now for the bright colors, balance of slightly sweet and savory, and all in one dish for dinner. I routinely use millet or quinoa, but used both in this version. We had a stockpile of pumpkins in our house from last season’s harvest which I’ve by now mostly used up, but I noticed at our local farmers market last weekend that winter squash and pumpkins are still going strong—locally we tend to have them until mid to late March. If they’re less available near you, swap them out for some other seasonal vegetable – or leave out completely.
Winter Tabbouleh, serves 4-6
1 small pumpkin or winter squash (about 2 cups cubed)
1 cup millet or quinoa or a combination of both
2 cups water or vegetable broth
¼ tsp. cinnamon
1 cup cilantro
½ cup mint
3 green onions
¼ cup walnuts, chopped and lightly toasted
¼ cup goji berries
2 cups cooked garbanzo beans
1-2 handfuls spinach or other greens, optional
2 Tbs. apple cider vinegar
2 tsp. honey
1 Tbs. olive oil
salt and pepper to taste
- Heat oven to 400 degrees F.
- Cook millet by combining with 2 cups of water or broth, along with the cinnamon, in a medium saucepan and bring it to a boil. Turn down to a simmer, cover and cook until the liquid is completely absorbed, 25 minutes. Set aside to cool.
- Place the squash cubes on a baking sheet with a little water. Bake for 25-35 minutes until the squash is soft. Alternatively, you can bake the squash whole until soft, then peel off the skin and chunk into pieces. This is my preferred quick-prep-ahead method lately.
- In a large bowl, toss together the garbanzos, cilantro and mint, gojis, toasted walnuts, cooked squash and green onions. Then add the millet and spinach greens and give it all a good stir. Finish it off with the apple cider vinegar, honey, olive oil and salt and pepper to taste. Serve warm or at room temperature.