Digestive Health
Fiber can help add bulk to stool, support normal bowel movements and help keep material moving through the digestive tract.
The Fiber Guide
The science, statistics and practical facts behind one of the most overlooked nutrients in the American diet.
THE FIBER GAP
Most Americans Aren't Getting Enough Fiber
Fiber is an essential part of a healthy diet, but the average American consumes only about 15 grams of fiber per day. Recommended intake for adults generally ranges from 21 to 38 grams per day, depending on age and sex.
90%+
of Americans don't meet recommended fiber intake levels.
In other words, the typical American diet can leave a substantial fiber gap.
Source: Mayo Clinic
HOW MUCH DO YOU NEED?
What's Your Daily Fiber Target?
Fiber needs vary by age and sex. The National Academy of Medicine recommends the following daily amounts for adults:
| Group | Recommended Fiber |
|---|---|
| Women age 50 or younger | 25 g/day |
| Women over age 50 | 21 g/day |
| Men age 50 or younger | 38 g/day |
| Men over age 50 | 30 g/day |
Source: Mayo Clinic
WHY FIBER MATTERS
Fiber Does More Than Keep You Regular
Fiber plays an important role throughout the body. Its effects extend beyond digestion to the gut microbiome, cardiovascular health, blood sugar regulation and feelings of fullness.
Heart Health
Higher dietary fiber intake has been associated with a lower risk of cardiovascular disease and coronary heart disease.
Gut Health
Certain types of fiber are fermented by gut bacteria and can support a diverse and healthy gut environment.
Blood Sugar & Metabolism
Certain fibers can slow digestion and carbohydrate absorption, and research has associated higher fiber intake with improved markers of metabolic health.
Fullness
Fiber can add volume to food and may help increase feelings of fullness and satisfaction after eating.
FIBER & DIGESTION
Constipation Is More Common Than You Might Think
16%
of U.S. adults experience symptoms of constipation.
Among adults age 60 and older, that number rises to approximately 33%.
Constipation isn't simply "not going." Symptoms can include:
- Fewer than three bowel movements per week
- Hard, dry or lumpy stools
- Difficulty or pain when passing stool
- Feeling like you haven't completely emptied your bowels
Fiber can help by adding bulk to stool and supporting normal movement through the digestive tract. Adequate fluid intake is also important when increasing fiber.
Source: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
WHAT IS FIBER?
Fiber Is a Carbohydrate Your Body Doesn't Fully Digest
Unlike many other carbohydrates, dietary fiber passes through much of the digestive system relatively intact.
That doesn't mean fiber is doing nothing.
Depending on the type of fiber, it can:
- Add bulk to stool
- Hold water
- Slow digestion
- Influence blood sugar absorption
- Help manage cholesterol
- Support beneficial gut bacteria
- Produce short-chain fatty acids during fermentation
Source: Mayo Clinic
FIBER & YOUR GUT
Your Gut Bacteria Eat Fiber, Too
Certain fibers are fermented by microorganisms in the colon. During this process, gut bacteria produce compounds including short-chain fatty acids.
Fiber
from your diet
→
Gut Bacteria
ferment certain fibers
→
Short-Chain Fatty Acids
produced during fermentation
This is one reason that fiber is about much more than simply "roughage." Different fibers can behave differently in the gut, and eating a variety of fiber-rich foods can support a diverse gut microbiome.
Source: Mayo Clinic Press
FIBER & HEART HEALTH
Fiber Isn't Just About Digestion
Research has consistently found an association between higher dietary fiber intake and lower cardiovascular risk.
~9%
lower cardiovascular disease risk was associated with each
additional 7 grams of dietary fiber per day in one large
systematic review and meta-analysis.
The study included 22 prospective cohort-study publications and found an inverse association between total dietary fiber intake and cardiovascular disease and coronary heart disease.
Importantly, this is an association, not proof that adding exactly 7 grams of fiber directly causes a 9% reduction in cardiovascular disease risk.
Research: Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis
FIBER & METABOLIC HEALTH
Fiber Can Change How Your Body Handles Carbohydrates
Certain types of fiber can slow digestion and the absorption of carbohydrates. This can affect how quickly glucose enters the bloodstream.
Research has also found associations between higher fiber intake and improvements in several markers of metabolic health, including measures of blood glucose control and insulin resistance.
The effects can vary depending on the type of fiber, the amount consumed and the overall dietary pattern.
FIBER & FULLNESS
Fiber Can Help You Feel Fuller
Fiber can add volume to food and slow aspects of digestion. Certain fibers can also influence how long food remains in the digestive system.
As a result, fiber can be one useful component of a diet designed to support fullness and appetite management.
But Fiber Isn't a Magic Weight-Loss Ingredient
Fiber can support a healthy eating pattern, but eating more fiber by itself doesn't guarantee weight loss. Overall diet, activity, energy intake and many other factors matter.
FIBER & COLORECTAL HEALTH
Fiber & Colorectal Health
Research has found an association between higher dietary fiber intake and lower colorectal cancer risk.
~10%
lower relative risk of colorectal cancer was associated with
each additional 10 grams of daily dietary fiber in one
systematic review and meta-analysis.
That analysis included 25 prospective studies examining dietary fiber and colorectal cancer.
Important:
These findings describe an association observed across studies. Fiber should not be considered a treatment for cancer or a guarantee against developing cancer.
FIBER & LONG-TERM HEALTH
Fiber Is Connected to More Than One Aspect of Health
A 2025 umbrella review examined 33 meta-analyses covering 38 health outcomes and more than 17 million individuals.
The review found that higher dietary fiber intake was associated with lower risk across many chronic health outcomes. Particularly strong evidence was identified for cardiovascular mortality, while highly suggestive evidence was found for several other outcomes including cardiovascular disease, coronary heart disease and all-cause mortality.
17+ million
individuals represented across the meta-analyses examined.
MYTHS & FACTS
Common Fiber Misconceptions
✕ MYTH
"Fiber is just for constipation."
✓ FACT
Fiber plays roles in digestion, gut microbiome health, cardiovascular health, blood sugar regulation, cholesterol management and fullness.
✕ MYTH
"The more fiber you eat, the better."
✓ FACT
More isn't automatically better for everyone. Increasing fiber too quickly can cause gas, bloating and abdominal discomfort. Gradually increasing intake gives your digestive system time to adapt.
✕ MYTH
"Fiber always relieves constipation."
✓ FACT
Fiber can help with constipation, but different fibers behave differently. For some people, suddenly adding large amounts of certain fibers can actually make bloating or discomfort worse.
✕ MYTH
"If fiber makes me gassy, I'm intolerant to it."
✓ FACT
A sudden increase in fiber can temporarily cause gas and bloating as your digestive system and gut microbes adapt. Gradually increasing fiber can help.
✕ MYTH
"All fiber works the same way."
✓ FACT
Different fibers have different properties. Solubility, viscosity, fermentability, food source and how a particular fiber interacts with the gut microbiome can all matter.
✕ MYTH
"I can get all my fiber from a supplement."
✓ FACT
Fiber supplements can help people increase their intake, but whole foods provide fiber alongside vitamins, minerals and other beneficial compounds. A variety of fiber-rich foods is generally a better overall strategy.
Sources: Mayo Clinic | Mayo Clinic: Dietary Fiber
HOW TO GET MORE FIBER
Start Low. Go Slow.
If you're currently eating a low-fiber diet, jumping straight to a high-fiber intake can leave you feeling bloated and uncomfortable.
Instead, gradually increase your fiber intake and give your digestive system time to adapt.
1
Increase Gradually
Add fiber-rich foods slowly rather than making a dramatic overnight change.
2
Drink Enough Fluids
Adequate fluid intake is particularly important when increasing fiber.
3
Eat a Variety
Include different sources of fiber such as fruits, vegetables, beans, whole grains, nuts and seeds.
4
Give Your Body Time
Your digestive system and gut microbes may need time to adjust to a higher fiber intake.
Source: Mayo Clinic
FOOD SOURCES
Where Does Fiber Come From?
Fiber naturally occurs in a wide variety of plant foods. Eating different sources can help provide different types of fiber and other nutrients.
Beans & Legumes
Lentils, black beans, chickpeas, peas and other legumes can be especially fiber-rich.
Fruits
Berries, pears, apples and many other fruits provide fiber along with vitamins and other nutrients.
Vegetables
Vegetables such as broccoli, carrots, potatoes and Brussels sprouts contribute fiber to the diet.
Whole Grains
Oats, barley, whole-wheat products and other whole grains can contribute substantial amounts of fiber.
Nuts & Seeds
Chia seeds, flaxseed, almonds and other nuts and seeds can provide concentrated sources of fiber.
Fiber-Rich Foods
Fiber can also be incorporated into foods such as snacks, cereals, bars and other everyday foods.
Source: Mayo Clinic
FIBER DOESN'T HAVE TO BE BORING
You Don't Need to Live on Bran Cereal
Getting enough fiber doesn't have to mean completely changing the way you eat.
Beans. Berries. Vegetables. Seeds. Whole grains. And yes, even chocolate.
HAC was created to make it easier to incorporate meaningful amounts of fiber into foods you actually want to eat.
THE SCIENCE
Fiber Research Library
The information on this page is based on systematic reviews, meta-analyses and information from major medical and scientific organizations.
The impact of dietary fiber consumption on human health
A 2025 umbrella review covering 33 meta-analyses, 38 health outcomes and more than 17 million individuals.
View research on PubMed →Dietary fibre intake and risk of cardiovascular disease
Systematic review and dose-response meta-analysis examining dietary fiber intake and cardiovascular disease.
View research on PubMed →Dietary fibre, whole grains, and colorectal cancer
Systematic review and dose-response meta-analysis examining dietary fiber, whole grains and colorectal cancer risk.
View research on PubMed →Dietary fiber and cardiovascular risk factors
Umbrella review examining the relationship between dietary fiber and glycemic control, lipid profiles, inflammation and blood pressure.
View research on PubMed →Dietary fiber and multiple health outcomes
A large umbrella review of systematic reviews and meta-analyses examining associations between fiber intake and multiple health outcomes.
View research on PubMed →Mayo Clinic: Dietary Fiber
An overview of dietary fiber, its types, health benefits and recommended intake.
Read the Mayo Clinic guide →NIDDK: Definition & Facts About Constipation
Information from the National Institute of Diabetes and Digestive and Kidney Diseases about constipation and how common it is in the United States.
Read the NIDDK information →The information provided on this page is for educational and informational purposes only. It is not intended to diagnose, treat, cure or prevent any disease or medical condition. Individual nutritional needs vary. If you have a medical condition, digestive disorder or other health concern, speak with a qualified healthcare professional about your individual dietary needs. The research cited on this page includes observational studies, systematic reviews, meta-analyses and other forms of scientific evidence. Associations found in observational research do not necessarily establish cause and effect.