You’ve known for a long time that fiber is good for you, and perhaps you know that it helps move things along, so to speak. Fiber is one of the best substances to ensure regular bowel movements and healthy stools.
But there is so much more to fiber – fiber is a large family unto itself, teeming with such members as fructooligosaccharides, and more. Each branch of the fiber family tree has its own activities in the body. To understand the branches and how they work, why they are unique, let’s discuss what is dietary fiber and why it is important to overall human health.
What Is Dietary Fiber?
Dietary fiber is considered a necessary part of a healthy, wholesome diet along with the macronutrients fats, proteins and carbohydrates. Every day the body requires these in balance to function optimally.
Fiber is found in whole grains such as rye and barley, in beans, nuts, seeds and in fruits and vegetables. There are two types of fiber – soluble fiber and insoluble fiber; like yin yang, you need both to be whole and in balance.
Soluble Fiber: This type of fiber is the active fiber. It acts like a sponge, absorbing water and turning into a gel. As this fiber-gel moves through the GI tract, it also grabs and holds onto cholesterol. This unabsorbed cholesterol is excreted from the body. Hence, the allowable claim you see on many labels about fiber helping to lower cholesterol.
Insoluble Fiber: Inactive, this fiber remains intact and doesn’t bind to water or any substance. However, its presence helps promote bowel regularity as it helps provide healthy bulk to stools.
So you can see that both types of fiber are utilized by the body for bowel regularity and cholesterol. Consuming fiber also helps manage weight. Fiber-rich foods tend to make you feel full faster than dishes or meals heavy in carbohydrates or sugars, so you don’t eat as much. In tandem, fiber-rich foods tend to be lower in calories.
Prebiotics: Fiber’s Emerging Superpower
Quick: what else is fiber great at doing in your body?
If you answered, “feeding my microbiome,” you are correct!
There is a class of fiber called “prebiotics.” Although first identified and so named only recently (1995), this word is somewhat confusing, as the prefix “pre” means “before.”
The reason the word “prebiotic” may seem confusing is that it can sound as if the prebiotic transforms into a probiotic. It doesn’t. A prebiotic is a substance that primarily is used as a fuel source for the microbes in your gut to continue life.
In fact, the definition of “prebiotic” has been revised in 2016 by the International Scientific Association for Probiotics and Prebiotics (ISAPP) to mean “a substrate that is selectively used by a host microorganism to produce a health benefit.”
The health-promoting microbes (probiotics) residing in your gut are living organisms, and as such, need good-quality food to not just survive but thrive. Probiotic bacteria that thrive are those that colonize, replicate and are nourished to defend against incoming pathogenic bacteria and other non-essential and irrelevant microbes that wander in and through the body.
What are Prebiotics?
Prebiotics in the diet are contained mainly in the insoluble (or non-digestible) fiber. When eaten, they pass intact through the upper part of your digestive system and when they get to the large intestine (bowel) they are snatched up by the communities of good bacteria and used as food. This nourishment is accomplished through fermentation. Believe it or not, YOU are a fermentation tank!
Prebiotics are currently characterized by three traits:
- They are unable to be digested by enzymes you produce in your gut.
- They are fermented selectively by specific probiotics residing in your gut (and you have a plethora)
- The fermentation process – wherein your good microbes themselves digest and utilize the prebiotic results in health benefits.
In summary, prebiotics are food-obtained substances that your digestive enzymes can’t break down and thus, when they enter into your large intestine, are fermented by your body to become ingested by bacteria to ensure they remain viable and productive.
Of several types of prebiotics, there are two common ones that are found in foods and in dietary supplements.
FOS not only acts as nourishment for your beneficial bacteria, studies have also shown that FOS can assist in weight loss through managing satiety. One study correlated short-chain FOS and its activity of colonic fermentation to early satiety. The study showed that the supplemental prebiotic increased breath hydrogen, a marker of fermentation, and that the women in the study showed marked reduction in food intake. And another study in obese individuals taking FOS or placebo for 12 weeks showed weight loss in the FOS group while a weight gain in the placebo group.
Also, FOS has been shown in several studies to augment the body’s ability to absorb nutrients during digestion. In particular, FOS has been shown to increase calcium absorption, and bone mineral density.
Inulin is a prebiotic found in high amounts in chicory, but this may cause sensitivities and even intolerances in some individuals. One placebo-controlled study using two inulin fibers in healthy subjects with no GI conditions found that the inulin tended to create some mild GI symptoms, notably bloating and flatulence.
Fermentation is how prebiotics are utilized by your gut’s beneficial bacteria; they both do this through an action called saccharolytic metabolism. Both Lactobacillus and Bifidobacteria populations tend to have preferences of prebiotic fibers they consume. For example, Lactobacillus prefer fructooligosaccharides and inulin, while Bifidobacteria also tend to like prebiotics xylooligosaccharides and galactooigosaccharides.
When your probiotic populations are well fed, you experience healthier digestion with fewer bouts of post-prandial (after eating) issues such as bloating, gas or griping, as well as better resistance to colds and other ailments.
What are the Foods Highest in Prebiotics?
There are several commonly sold natural foods that are high in prebiotics. Diet-wise, a good rule of thumb is that if the raw material is high in fiber, it is a good source of prebiotics. The list of super high fiber foods is topped by raw chicory root (with an approximate 65% fiber content by weight), Jerusalem artichoke at 64%, dandelion greens (found and foraged in grounds not subject to pesticides or herbicides) at 24%. Other sources are in the allium family – garlic, leeks, onion.
Keep in mind that the raw form is typically the best form as cooking tends to degrade and destroy nutrient content, including weakening the ability of the fiber to act as a prebiotic once it enters the fermentation tank (large intestine).
It is important to know that while all prebiotics ARE fiber – not all fiber substances are prebiotics. And yes, you can certainly feed your microbiome with a diverse array of prebiotic-containing foods, but supplementing with prebiotics is also a great idea in case you don’t get enough on a regular (daily) basis.
If you are someone who eats a mindfully healthy diet but don’t feel you can obtain enough FOS through the foods mentioned above, you can and should supplement with it. And you don’t necessarily have to swallow more pills; FOS is available in easier-to-take forms such as a micro-shot, which is exactly what it sounds like: a quick gulp of refreshing liquid.
Remember, if you are going to take probiotics, you need to feed them with fiber!