is an important part of a healthy diet.
In fact, eating enough fiber is said to keep your gut healthy
and protect against type 2 diabetes and weight gain (1).
It’s recommended that men aim for 38 grams of fiber per day,
while women should aim for 25 grams (2).
However, not all dietary fiber is created equal, and different
types have different health effects (3).
This article explores how dietary fiber works to protect your
health and how much of it you should eat.
Different Types of Fiber
is a group of carbs that humans can’t digest. It’s found in all
plant foods, including fruits, vegetables, nuts, seeds and
Because dietary fiber refers to a diverse group of different
carbs, it can be categorized in various ways.
However, it’s usually grouped into one of the following
categories, according to its solubility:
Insoluble fibers: These fibers don’t
dissolve in water. They generally pass through your gut
unchanged and add bulk to your stool.
Soluble fibers: These fibers absorb water in
your gut to form a gel-like paste. This slows down the
digestion of nutrients in your food.
Most foods contain both soluble and insoluble fibers, but
usually have more of one type than the other.
In general, foods that contain mostly insoluble fibers include
whole grains, wheat bran and some fruits (like avocados) and
vegetables (such as celery and cauliflower).
Good sources of soluble fibers include oats, flaxseeds, beans
and lentils, as well as some fruits (such as berries and
bananas) and vegetables (like broccoli and carrots).
Bottom Line: Dietary fiber is usually
classified as soluble or insoluble. It’s found in all plant
foods, including fruits, vegetables, nuts and seeds.
Fiber Can Help Keep Your Gut Healthy
Eating fiber is said to help maintain regular bowel movements
In fact, one study found that as many as 77% of people with
chronic constipation experienced relief by simply eating more
They also increase the production of some important nutrients,
including short-chain fatty acids like butyrate, which are
thought to promote a healthy immune system and good gut barrier
function (9, 10, 11).
Having a strong gut barrier is important. It helps keep you
healthy by preventing things like viruses and harmful bacteria
from entering your body.
foods include oats, bananas and berries.
However, it’s currently not fully known which types and amounts
of fiber best promote the growth of good bacteria in your gut
Bottom Line: Eating adequate amounts of
dietary fiber can prevent constipation. Soluble, prebiotic
fibers help maintain the balance of good bacteria in your
Fiber Can Make You Feel Full and Help You Lose Weight
Including fiber-rich foods in your diet can
help you lose weight.
This was reflected in one review of over 50 studies, which
estimated that people who ate 14 grams more fiber per day
automatically reduced their calorie intake by around 10%
Interestingly, this effect was larger in people who were
overweight or obese.
However, a recent review found that only around 39% of fibers
helped reduce hunger. Of these, just 22% resulted in a
reduction in the amount of food eaten at a meal (17).
Viscous, soluble fibers — which form a thicker, sticky gel in
your gut when they absorb water — are the most effective at
keeping you full (18).
Food sources of viscous, soluble fibers include flaxseeds,
legumes and oats.
Emerging research is also investigating whether supplementing
with specific types of fiber may help weight loss (19).
However, in general, fiber supplements haven’t always been
found to be particularly useful (20).
Nevertheless, it can’t be presumed that fiber supplements have
the same health benefits as whole-food fibers. This is because
whole-food fibers come with many other beneficial nutrients
Bottom Line: Viscous, soluble fibers are
thought to be the most helpful fibers for weight loss. If you
don’t eat much fiber, increasing your intake by around 14
grams per day could help you lose weight.
Fiber Can Lower Blood Sugar Levels and Protect Against Type 2
Regularly eating the recommended amount of fiber is thought to
help prevent and treat type 2 diabetes.
One study followed over 75,000 people for 14 years and found
that those who ate more than 15 grams of fiber per day had a
significantly lower risk of developing diabetes (27).
Additionally, this risk was lowest in the group that ate the
most insoluble fiber.
Another study found that people eating 3–5 servings of whole
grains per day had a 26% lower risk of type 2 diabetes
If you already have diabetes, it’s also thought that eating
more fiber could help you control
your blood sugar levels.
This is because soluble fibers slow down the digestion and
absorption of sugars, resulting in a more gradual rise in blood
sugar levels and fewer blood sugar spikes.
Bottom Line: Regularly eating dietary fiber
may help prevent type 2 diabetes. Eating fiber may also
improve blood sugar control in people with type 2 diabetes.
Does Fiber Have Any Negative Effects?
While increasing the amount of fiber in your diet should
benefit your health, doing so can sometimes cause problems.
If you aren’t used to eating a lot of fiber, suddenly
increasing your intake by a large amount could result in
digestive symptoms like bloating, pain and gas.
Moreover, if you are chronically constipated, you may find that
increasing the amount of fiber you eat doesn’t help. It may be
that reducing your fiber intake is the best way to improve your
However, this is usually only the case if you have chronic
constipation that isn’t caused by an inadequate fiber intake
Also, those with irritable bowel syndrome (IBS) may find
fiber-rich foods problematic.
Bottom Line: Eating too much fiber can be a
problem, especially if you have a functional bowel problem
So How Much Fiber Should You Eat?
Unfortunately, most people don’t eat much fiber. In the US,
most people eat less than half of the recommended daily amount
That said, the current evidence does not indicate which type or
amount of fiber is optimal for your health.
Fiber from whole foods comes with many other healthy nutrients.
So it may be that the type of fiber and where it comes from is
more important than the total number of grams.
Therefore, for most people, eating enough fiber doesn’t require
obsessing over each and every gram.
Simply aiming to include healthy
high-fiber foods with most of your meals should be