Fiber Essential, but Why?
Those who read about health in the news, may have noticed quite a few articles in the last several years about the beneficial health effects of the microbiome. As the medical community has begun to understand the importance of microbes to the human body, the scientific consensus has become that a healthy microbiome is necessary for optimal physical and mental well-being. Therefore, the pressing question becomes, “what is the best way to support my microbiome?”.
We have written about things we all can do to foster the health of our vital microbes. We have discussed the importance of eating a varied diet including lots of fermented foods. We have outlined the harm that can be caused to our microbiome by alcohol, food additives such as preservatives and particularly antibiotics. We have warned that chemicals used in farming can disrupt the mix of microbes in our gut, giving us good incentive to buy organically whenever possible. Even stress can affect the mix of microbes in the gut.
But there is an easy change that we can all make that will make our gut microbes thrive. Researchers have found that fiber (in particular roughage) is a star player in keeping our microbiome working as it should. Roughage is the component of fiber that can’t be digested by us. It is the fibrous material in fruits, vegetables, nuts, and grains.
Doctors, nutritionists, and nagging parents have been advising for years that it is important to include a lot of fiber in the diet, without fully understanding why it was good for us. The somewhat puzzling thing about this advice, however, is that most of the fiber we eat is indigestible and provides no nutritional value whatsoever, but longitudinal studies show that people who eat more fiber in their diets live longer, on average, than those who don’t, and have lower rates of diabetes, heart disease and arthritis. So what about it is beneficial for health?
An early theory behind why eating roughage is good for us was that it “roughs-up” (hence roughage) the digestive tract as it passed through, causing the body to create mucous that helps smooth along the digestive process. Another theory held that the roughage absorbed water while in the digestive tract, thereby increasing the volume of stool. More voluminous stool keeps bowel movements regular, with waste product and food moving through the digestive tract. Those both sounds like good reasons to eat fiber, but are they enough to promote a statistically longer life-span?
Recent studies have revealed that there is another reason to eat a lot of roughage – perhaps more important than those which were given to us in the past. We may not be able to digest roughage, but bacteria are very effective at it. Many health-promoting microbes that live in our digestive tracts need fiber to grow and thrive.
How Roughage Helps Gut Microbes to Help Us
Two researchers undertook studies, written about in the New York Times in 2018, to learn more about why fiber is good for us. What their research suggests is that fiber is good for us because feeds the multitudes of bacteria, which live in our guts and keep our digestion and immune systems working well.
Dr. Andrew Gewirtz from Georgia State University and his colleagues attempted to determine whether fiber affected the gut microbiome in mice. Dr. Gewirtz initially fed mice a high fiber diet and then examined which and how many different bacteria were found in their guts.
They then dramatically reduced the overall fiber in the mice’s diet. The overall population of gut microbes dropped 10 fold after their change in menu.
Fredrik Bäckhed, a biologist at the University of Gothenburg in Sweden, decided to take this experiment one step further. After initially feeding the mice a fiber-rich diet, he and his colleagues then altered the diets by reducing fiber and adding lard, sugar and lots of protein. The doctors found that the mix of microbes changed dramatically – many previously common species became rare and previously rare species became numerous.
When Dr. Bäckhed’s team examined the mice themselves, the found that inflammation in the digestive tract had increased significantly in the mice within only a few days after the low-fiber diet was initiated. Blood suger levels went up. Their body fat content increased.
The team then added fiber (inulin) into a second group of mice that were being fed the same high-fat, unhealthy diet as the first group. The inulin seemed to counteract many of the unhealthy effects of the high-fat diet.
Dr. Gewitz also fed inulin, in even higher doses than the amounts given by Dr. Bäckhed’s team, to a set of mice subjects that were also on a high-fat, low-fiber diet. It seemed to protect the mice from many the ill-effects as compared to their mouse compatriots on the same diet that weren’t given the inulin. The diversity and number of gut microbes of in these junk-food fed mice remained as high as the control group of mice fed only the high-fiber diet. Mucous levels, which protect the gut from inflammation, were normal and the mice put on less weight than their low-fiber fed counterparts.
As the number and diversity of gut microbes increased in the mouse microbiomes when fiber was included, health of the mice improved – even with an otherwise unhealthy diet.
Why Should We Care that our Gut Bugs are Well-fed?
It seems that when our gut microbes are fed a diet rich in fiber, not only do they thrive and multiply but they nurture our well-being as well.
The mucous membrane they produce in our digestive tract lines it, keeping bacteria and pathogens from entering our body. This reduces chronic inflammation, which can be a precursor to many harmful diseases such as Diabetes 2, insulin resistance syndrome, arthritis, and inflammatory bowel disease (IBD).
Our microbes also support our immune system by directly attacking and killing harmful bacteria and viruses that enter the digestive tract. They signal to our immune system by means of neurotransmitters nerve to produce more disease fighting cells when they sense the presence of a threat.
Many microbes help us to extract energy and nutrients from our food. Certain microbes produce vitamin K, which our bodies cannot produce. They even produce food for us. As they digest roughage, the microbes produce enzymes that are used by our bodies for energy.
It has been well-documented that having a healthy mix of microbes promotes weight control. Some microbes are better at extracting energy from food than others. Additionally, the mix of microbes in the gut can affect the types of food cravings a person can have by means of neurologically active chemical messengers they produce. Yeast, for example, thrive on sugar and carbohydrates. Higher levels of yeasts in the gut may lead to cravings for sweets, bread and pasta.
Plentiful and diverse gut microbes contribute to mental health. Extensive studies have revealed that a healthy gut environment leads to less depression, anxiety and obsessive compulsive behaviors.
When dietary experts tell us to do something, but do not make a compelling argument for why it is in our best interest, it can be difficult to follow their advice. However, with what we now know, it’s much easier to explain the importance of dietary fiber. Understanding how fiber nourishes gut microbes and how a healthy microbiome improves human health provides all the motivation we need to eat plenty of it.
What’s the Best Way to Get Roughage?
The American Heart Association recommends getting 25 – 30 grams per day from food. Unfortunately, a western diet, on average, only provides 15 grams per day.
If following recommended guidelines feels overwhelming or unpalatable, instead focus on how much you have been eating and try to increase it. Including more roughage in your diet than you did before, can still lead to health improvements. Slowly, over time continue to eat more and enjoy the pay-off to your well-being.
Fiber contains two components: soluble and insoluble fiber. Soluble fiber absorbs water during the digestive process, which bulks up the stool and keeps digestion regular. Insoluble fiber is the indigestible roughage that our healthy gut bugs love to eat. Although each type of fiber is beneficial, getting more insoluble fiber is the goal to increase the amount and diversity of microbes needed in a healthy microbiome. Insoluble fiber is highest in whole grains, brown rice, the edible peels of seeds and fruit, vegetables and legumes.
Ideally, whole grains are a reliable source of roughage and should be included at each meal.
A simple switch from white flour to whole meal flour can increase fiber. Look for cereals that include at least 5 grams of fiber per serving. Keep oat bran and / or wheat germ in the kitchen and find creative and delicious ways to use them in your regular diet such as sprinkling on salads, yoghurt or cereal, or use it in baking.
Brown rice is a decent source of fiber. If you don’t love it, try gradually mixing in a little bit of brown rice into your white rice, gradually increasing the ratio as your tolerance for it improves.
Legumes, Nuts and Seeds
Not only is “Meatless Monday” good for the environment, if you can substitute legumes such as kidney beans, soybeans or lentils for meat in your meals that day, it will give you a dietary boost.
Garbonzo beans, black beans or kidney beans are delicious in a salad, adding a little extra pizzazz to the normal lettuce, tomato, and cucumber stand-bys.
Not only does the protein in nuts and seeds fill us up, making us less tempted to snack, these superfoods also contain a hefty amount of roughage. Instead of cheese and crackers before dinner, have a handful of nuts. An almond butter sandwich is a great alternative to deli meats a few days a week. Sunflower seeds are yummy sprinkled on a salad. Include walnuts or pecans in your chocolate chip cookies.
Fruits & Vegetables
From a microbiome perspective, the focus should be on vegetables, which contain more roughage than fruit does, in general. Some fruits are high in insoluble fiber, however. Pineapple is great, as are unripened bananas. Avocados are a stand-out. Berries, such as raspberries and strawberries, because of their small seeds, pack a high dose of roughage. Guava and Asian Pear are also delicious sources of insoluble fiber. If you eat the seeds (and no, a watermelon won’t grow in your stomach!), you can add watermelon to the list as well.
All vegetables contain fiber, but some are better than others. Dried vegetables, such as sun dried tomatoes are good. Artichokes are not only a treat, but are also a high roughage food. Peas are good too, particularly if you consume the pod.
Cruciferous vegetables contain a high amount of roughage. They include:
- Bok Choy
- Brussels Sprouts
- Collard Greens
The goal is to consume at least three servings a day, but more-than-before is also a worthy goal.
Providing fiber supplements to obese children in a 2017 research study at the University of Calgary showed that their microbiome benefited from an inulin (similar to what was given to the mice in the studies outlined above) supplement. On average, the number and diversity of healthy microbes increased in the kids’ guts. It also appeared to help the children lose fat, particularly the unhealthy fat surrounding their abdomens.
Although these sorts of dietary supplements appear to provide many of the same benefits to the microbiome as dietary fiber, they do not contribute calcium, protein and micro-nutrients in the same way as do the foods discussed above. The goal should always be to eat less processed / manufactured foods, rather than more. However, if for some reason that is the only way to obtain sufficient roughage, supplementing with powdered fiber could be considered.
Now the mechanism behind why roughage is so good for us is better understood, it is easier to pay attention to the amount of fiber we are getting in our food. If on the margin we are making better decisions on a daily basis, our healthy gut bugs will thank us and reward us as well.