Evidence Based Research To fulfill our commitment to bringing our audience accurate and insightful content, our expert writers and medical reviewers rely on carefully curated research.
Read Our Editorial Policy
Americans are insanely deficient in fiber, thanks mostly to processed foods, to an extent that majorly impacts public health.
In an era of TV remotes with built-in bottle openers and self-twirling pasta forks, it’s no surprise that we’ve become too lazy to chew.
It sounds crazy on paper, but really—foods that require more chewing have been steadily declining, which means fiber consumption has tanked as well.
At the same time, processed foods that have had the fiber flayed away (even those that are marketed as healthy) are lining our pantries like the grocery store aisles they came from.
The result is a truly epidemic-level fiber deficiency often dubbed by experts as the “fiber gap,” which comes with a range of harmful effects on public health.
Before we get into the gloomy statistics, a quick introduction to this nutrient that we hear about all the time, but know very little about.
Fiber is a broad spectrum of plant-based material that the body can’t digest.
According to Diet and Health: Implications for Reducing Chronic Disease Risk, a guide from the National Research Council Committee on Diet and Health, dietary fiber consists of tightly clumped sugar molecules (polysaccharides), cellulose, pectin, guar gum, and other obscure-sounding plant constituents.
Insoluble fiber doesn’t dissolve in water, while soluble fiber turns into a goopy substance (that still isn’t digested).
Fruits, vegetables, nuts, seeds, and grains are generally high in some form of fiber.
To be discrete, we’ll just say that, when consumed with digestible foods, fiber simply “comes along for the ride,” entering and exiting the body intact while the rest of the food is digested.
So, if it isn’t even digested, how could it be so important?
The answer lies in what it does while it’s in the body, which involves keeping the food moving (anti-constipation), slowing down glucose absorption, supporting the benevolent bacteria that live in our stomachs, promoting heart health, and much more as listed below.
Since most people are seriously deficient in fiber, researchers have used the symptoms of deficiency as a way of outlining its benefits.
The FDA has created a poster on dietary fiber that we recommend for anyone looking for a quick way to learn more, as it contains information about what it is, where it’s found, what it does, and how to increase your daily intake.
Speaking of, the FDA recommends a daily intake of 28 grams for adults following a 2,000-calorie/day diet.
Most Americans consume a paltry 15 grams of fiber a day, meaning we’re literally missing the mark by just under 50%.
To provide some scale, here’s a small list of fiber-rich foods, complete with their approximate fiber content:
“But my all-natural fruit bars from (insert huge corporation here) are made with real fruit. I can’t be that deficient.”
We’ll counter with a question: When’s the last time you found a stem, stalk, peel, or husk in your nutri-whatever bar?
Understanding just how damaging the fiber gap is requires a closer look at the roles of fiber in the body.
In the spirit of optimism, we’ve listed several of fiber’s major benefits for the body (leaving the pitfalls of deficiency implied) below.
According to this academic article from the University Hospitals Coventry and Warwickshire of the UK, a fiber-rich diet significantly outperformed placebo for chronic constipation relief in five of seven studies.
This is the most concretely understood mechanism; keeping everything moving with sheer bulk.
Fiber promotes a feeling of fullness more effectively than low-fiber and/or processed foods, and has been shown in research to support weight loss.
This is really a double bonus, since increasing fiber intake will naturally encourage swapping out less healthy foods for natural, plant-based alternatives while you drop a few pounds.
To be clear, weight loss isn’t the primary objective of a high-fiber diet, and in most cases, you will lose a small or moderate amount of weight over a long period of time after upping your fiber consumption.
Perhaps the most clinically relevant benefit of fiber, or at least tied with heart disease prevention, is the ability to stave off insulin resistance.
According to a fact sheet by the Centers for Disease Control (CDC), more than 34 million Americans have diabetes, and 90-95% of them are type 2 diabetics.
Thankfully, fiber has been proven time and time again to effectively keep blood sugar levels lower after carbohydrate consumption.
Dozens of studies have experimented with increasing the fiber-to-carbohydrate ratio and fiber alone, and almost all of them have come to this conclusion.
In simplest terms, fiber “waters down” sugars, forcing them to take longer to absorb into the bloodstream.
Importantly, studies like this one from Kagawa Nutrition University in Tokyo have proven that this effect holds for type-two diabetics.
The 100 trillion bacteria living in and around the human digestive tract also respond to fiber in a positive way.
There’s still much to learn about this microscopic community, but as researchers from the University of Michigan Medical School demonstrated, depriving (some of) them of fiber comes with serious consequences.
In the study, mice who were deprived of fiber experienced “erosion of the colonic mucus barrier” that led to lethal colitis in many cases.
In other words, when there’s no fiber to eat, some forms of gut bacteria turn to the lining that protects the colon, which is very not good.
Other studies have pointed to a somewhat similar, but more general problem in which underfed bacteria promote systemic inflammation by limiting the production of substances that keep pro-inflammatory compounds in check.
Thanks to its ability to regulate weight, appetite, insulin levels, and the gut microbiome, researchers have found that fiber intake is inversely related with heart disease incidence.
In a meta-analysis by the University of Leeds (UK) that reviewed the results of 22 cohort studies, every seven grams of average daily fiber intake among participants was associated with a 6-12% decrease in cardiovascular disease prevalence.
Soluble fiber helps to regulate cholesterol by adhering to cholesterol particles, making it much harder for them to be absorbed into the bloodstream.
Finally, particulars aside, higher fiber intake has been associated with a longer lifespan.
In our article on the longevity diet, we talk about dietary influences on “telomeric aging.”
Telomeres are like protective bumpers that cap each end of our chromosomes.
As our cells copy themselves, the telomeres get shorter and shorter, until they are unable to sufficiently protect the important information encoded in the center of the chromosome, which leads to aging.
Fiber is among the select class of nutrients that can actually slow down this process.
When it comes to sound nutrition, no social media trend has come close to the wisdom imparted across the dinner table by your finger-wagging mother.
It may not be sexy, but the “old ways” still work—eat more fruits and vegetables, try out some nuts and seeds, and take it easy on the sugar.
A great way to start is by swapping out foods you already eat with similar, more fiber-dense alternatives (example: real fruit for fruit bars).
After upping your intake to at least 25 grams of fiber a day, the benefits will be as consistent as your trips to the bathroom.
Subscribe now and never miss anything about the topics important to you and your health.