There are plenty of heated debates about food, diet, and nutrition. Experts and influencers argue about carbs vs. fats, raw vs. cooked, whether you should take vitamin and mineral supplements, and where it’s best to get your protein.
I’m not saying those questions aren’t important, but they all miss the one nutrient critical to a healthy life that almost everyone is deficient in: fiber
Are you getting enough fiber? It depends on what you eat, of course. But in the words of Toy Story’s Magic 8 Ball, “don’t count on it.” Fewer than 10% of U.S. women and 3% of U.S. men get the recommended amount of fiber. In the U.K., more than 9 out of 10 adults fall short.
In places where people still eat relatively traditional diets, like many of the Blue Zones that are home to some of the planet’s longest-lived peoples, eating fiber-rich foods is par for the course. In fact, it may well be that fiber is a major factor in the longevity of Blue Zone residents.
A meta-analysis published in the American Journal of Epidemiology found that people who consumed the most fiber were 16% less likely to die during the following ten years, compared to those who ate the least.
Researchers analyzed 17 studies that included nearly a million participants and found that every 10 grams of fiber consumed per day cut mortality risk by 10%. To put that amount in perspective, one small cherry tomato weighs roughly 10 grams, according to my kitchen scale.
But why is fiber good for you? How can it benefit your health? How much fiber do you need daily? And how can you ensure you’re getting enough fiber in your diet?
What Is Fiber, Exactly?
Fiber provides structure to plant cell walls, functioning kind of like a skeleton. When you eat plants, your body does a great job of extracting macro and micronutrients, but it doesn’t manufacture the digestive enzymes needed to break down fiber. So that fiber passes through your digestive system intact.
That might sound like an argument for fiber being unnecessary, or even a problem. But wait — there’s more to the story. A lot more.
There are two types of fiber: soluble and insoluble. Each performs a different job in your body.
Soluble fiber dissolves into a gel in your digestive tract with the addition of water. It slows down digestion, which helps with blood sugar balance and cholesterol levels, as well as nutrient absorption. Good amounts of soluble fiber are found in foods like whole grains, beans, nuts, and seeds, as well as some fruits and vegetables.
Insoluble fiber adds bulk to your stools and acts like a broom, cleaning out your digestive tract. It promotes healthy bowel movements and also helps with insulin sensitivity. You can find good amounts of insoluble fiber in whole grains, vegetables, and wheat bran.
Both soluble and insoluble fiber are found naturally, to varying degrees, in all unrefined plant foods. Meat, dairy products, fish, eggs, added sugars, and oils, however, don’t contain any fiber. And processed foods made with refined flour generally contain very little, if any, because natural fiber is lost or removed in their manufacture.
Prebiotics and Resistant Starch
Soluble fiber does more than regulate the traffic in your digestive tract. While your body doesn’t have the digestive enzymes that can break it down into useful compounds, it “knows a guy.” Specifically, your gut is host to a veritable universe of bacteria, collectively known as your microbiome.
Like any universe, your microbiome includes many different characters; some helpful, some neutral, and some downright dangerous. Beneficial bacteria, known as probiotics, have the tools to metabolize fiber for energy. In that process, they also produce a wide range of compounds that are crucial to your health that you can’t make without them.
Prebiotics fall under the umbrella of soluble fiber and also serve as food for those beneficial “probiotic” gut bacteria. Prebiotic-rich foods include things like jicama, allium vegetables, legumes, and leafy greens.
Resistant starch is a type of indigestible, fermentable carbohydrate that also serves as a prebiotic. Whole grains, potatoes cooled after cooking (hello, potato salad!), and green bananas are all good sources of resistant starch. This type of starch improves insulin sensitivity and promotes the production of short-chain fatty acids in the gut, which keep your gut and immune system healthy. These fatty acids also circulate throughout your body, communicating with your cells and tissues to help regulate inflammation and promote healing.
Benefits of Fiber
The evidence for the health benefits of fiber is overwhelming. Let’s explore some of it here.
Fiber and Gut Health
Does fiber help you poop? Yes, it does! And being able to do so daily is more important than you might think. Constipation is not only uncomfortable, but it may also increase your risk for chronic diseases like cancer, hormonal imbalances, and even cardiovascular disease.
By speeding things along, fiber helps eliminate toxins from your digestive tract. The longer those toxins hang around, the more likely they are to be reabsorbed into your body through your intestines and wreak havoc on your health.
Fiber also benefits your digestive system by improving the composition of your microbiome. As we saw, certain fiber-filled foods are also prebiotics that feed your population of good gut bacteria. Increasing your fiber intake can alter your microbiota in as little as two weeks, enabling those beneficial bacteria to crowd out any “bad guys“ that could be causing gastrointestinal and other health issues.
Does Fiber Help You Lose Weight?
Consuming more fiber can indeed support weight loss. A 2019 study, the POUNDS Lost Study, asked overweight and obese participants to follow a reduced-calorie diet that provided at least 20 grams of fiber per day.
That number is worth putting in context. It’s well below the 25–40 grams per day recommended by the U.S. Institute of Medicine (the range depending on age and sex), but it’s significantly more than most Americans currently eat. So even that modest target represented a meaningful dietary shift for most participants.
Fewer than half of the participants consistently hit the 20-gram mark — those who did lost about 3 more pounds than those who fell short. One likely reason is that adequate fiber helped them more easily stick to their calorie targets.
So why does fiber help with weight management? A big part of the answer is satiety. Soluble fiber absorbs water in the gut and forms a gel-like substance that slows the absorption of sugars into the bloodstream and activates stretch receptors in your stomach. This is the physical signal that tells your brain you’ve eaten enough.
Fiber-rich whole foods reinforce this effect in another way. Compared to animal products and processed foods, whole plant foods tend to be higher in water and lower in fat, which means they deliver fewer calories per bite. You end up eating a satisfying volume of food while taking in fewer calories overall — and your stretch receptors do the rest, sending the message to your brain that it’s time to stop.
Fiber and Cancer Prevention
Fiber is an essential part of your waste removal system, constantly eliminating carcinogens before they become a problem. For instance, fiber works to prevent colorectal cancer by improving intestinal transit time — literally sweeping away carcinogens.
In a study at the National Cancer Institute called the Polyp Prevention Trial (PPT), published in the Journal of Nutrition, participants were put on a low-fat, high-fiber diet high in fruits and vegetables. Researchers focused on the recurrence of colorectal adenomas (polyps), viewing them as precursors or early warning signs of cancers that might take years or decades to show up clinically.
After adjusting for variables, it was found that the one food that made a difference in whether or not participants had a recurrence of adenomas was the amount of beans they consumed. The researchers note that for most study participants, beans were their primary source of dietary fiber.
Fiber’s anticancer benefits don’t stop at colorectal cancer. It also reduces the risk of cancers of the breast, prostate, mouth, and throat. A meta-analysis published in the BMJ found that every 10 grams of fiber consumed daily is associated with a 10% reduced risk of colorectal cancer, and a separate meta-analysis in the Annals of Oncology found the same 10-gram increase linked to a 5% reduction in breast cancer risk.
But perhaps the most striking finding comes from a long-term study published in Pediatrics that followed over 90,000 women for 20 years. It found that what you eat as a teenager and young adult may shape your breast cancer risk for the rest of your life. Women who consumed the most fiber during adolescence and early adulthood — around 20 grams or more per day — had a 24% lower risk of developing breast cancer before menopause. Every additional 10 grams of daily fiber in early adulthood was associated with a 13% further reduction in risk. And the women with the highest overall fiber intake reduced their lifetime breast cancer risk by 16%.
In other words, this isn’t just advice for adults trying to course-correct. If you have daughters, nieces, or young women in your life, or you are a young woman yourself, this is worth sharing and taking to heart.
Is Fiber Good for Your Heart?
Many cardiologists recommend eating oatmeal for breakfast. Their #1 reason? Oatmeal is a rich source of soluble fiber, and studies have found that it has a positive impact on cholesterol.
In fact, a review and meta-analysis of 22 different studies found that the more fiber people ate, the lower their risk of both cardiovascular disease and coronary artery disease.
One possible way dietary fiber achieves these effects might be its ability to reduce systemic inflammation markers associated with cardiovascular disease and other diseases. Its impact on inflammation is important for heart health because inflammation may be a risk factor for high blood pressure.
Fiber and Blood Sugar
Fiber helps regulate blood sugar. This is one of the reasons that many dietitians and other lifestyle medicine practitioners recommend that people with type 2 diabetes consume beans and other legumes. These high-fiber powerhouses help slow glucose absorption while regulating blood sugar over time.
In a study published in Nutrition Journal, researchers compared the glycemic response of traditional bean-and-rice meals with rice alone.
Seventeen men and women with diabetes were given either plain white rice, white rice with black beans, white rice with pinto beans, or white rice with red kidney beans. Then, researchers measured their blood glucose at 90, 120, and 150 minutes.
When they ate beans with their rice, the participants exhibited better blood sugar control. This makes sense, considering that beans and other legumes are good sources of resistant starch, which can improve insulin sensitivity and prime the body to move glucose from the blood into cells, where it can be stored or used.
So, whether you have type 2 diabetes, prediabetes, or just want to have a steadier blood sugar balance and improved insulin sensitivity, a high-fiber, plant-powered diet that includes beans may help you feel your best.
How Much Fiber Do You Need?
Dietary guidelines for fiber vary, but most countries and professional health agencies recommend intakes between 25 and 35 grams per day for adults. Although the U.S. updated its daily fiber reference value in 2016 from 25 to 28 grams per day for a 2,000-calorie diet — based on the long-standing standard of 14 grams per 1,000 calories — most adults are still getting only about half that amount daily.
While 28 grams of fiber would obviously be a step in the right direction, some experts believe we should aim much higher. The Physicians Committee for Responsible Medicine’s (PCRM) fiber recommendation, for example, is 40 grams per day.
Even that goal falls short of the 100-gram-a-day average that some researchers believe our ancestors may have been eating. They weren’t tracking their fiber intake on an app or hunting it down at a health food store. It was simply the tax they paid for eating wild plants. In those days, undomesticated fruits, veggies, and tubers were much tougher and woodier than the tender, sugary versions we find in modern supermarkets.
And in the absence of fancy kitchen gadgets, our progenitors often consumed the skin, seeds, and stems of these plants. Long story short: To get enough calories from plants, they had to eat massive volumes, which naturally brought a tidal wave of fiber into their digestive tract.
I don’t necessarily recommend eating twigs and banana peels to achieve those 100 grams a day. But if you’re eating the way most people do in the industrialized world, you could probably do with more fiber in your diet.
What Are the Best High Fiber Foods?
Now that you know the health benefits of getting enough fiber, what are some of the best fiber-rich foods you should be eating?
Given that fiber is best found in its natural state and fiber is found only in plant foods, fill your plate with fiber-rich foods, such as:
- Vegetables
- Fruits
- Beans and other legumes
- Whole grains
- Nuts and seeds
You can buy fiber supplements, which are probably better than nothing if your diet is largely devoid of fiber. That said, in most cases, they’re likely to be of limited value compared to whole plant foods, since they’re missing the beneficial vitamins, minerals, antioxidants, and phytochemicals also found in those foods.
This infographic, which is by no means comprehensive, can help you start your quest to find high-fiber foods.
How to Get Enough Fiber in Your Diet
Here are some easy ways to add more fiber to your diet:
- Choose whole grains instead of white bread and white flour products
- Choose beans over beef (or any other animal product)
- Double your veggie sides: Pile vegetables on your plate before you add anything else
- Start your day with oatmeal and berries instead of eggs, bacon, or commercial breakfast cereals
- Snack on fiber-rich foods, such as pears, sliced apples with peanut butter, or veggies and hummus
- Skip or reduce your consumption of meat, dairy, and processed foods like cookies, crackers, chips, and sodas
Specific foods vary in fiber content, but to gauge how much fiber to eat, it can be helpful to estimate the number of grams of fiber in different food groups.
The PCRM offers this information in a handy chart.
| Beans (cooked):
One serving = ½ cup |
7 grams |
| Tofu:
One serving = ½ cup tofu |
2–3 grams |
| Vegetables:
One serving = 1 cup |
4 grams
(lettuce is 2 grams) |
| Fruit:
One serving = 1 medium piece of fruit |
3–5 grams
1 cup of juice is one gram |
| Grains (cooked):
One serving = ½ cup |
1 gram in processed grains like white bread, white rice, processed cereal
2 grams in whole wheat bread and whole wheat pasta 3 grams in whole grain cereal and brown rice 4 grams in oatmeal 8 grams in bran |
| Meat, Poultry, and Fish | 0 grams |
| Eggs and Dairy | 0 grams |
| Soda | 0 grams |
To understand how much fiber you’re getting, here’s what you can do: Write down everything you eat and drink for one day and jot down your fiber score according to this chart.
You’ll notice that if your diet is made primarily from whole plant foods and includes plenty of beans, whole grains, fruit, and vegetables, you’re probably getting a good amount of fiber.
However, if you’re eating meat, dairy, and processed foods — like white bread, cookies, crackers, chips, and soda — it can be challenging to achieve the goal of 40 grams, or even 28 grams, of fiber per day.
How to Understand What Your Fiber Score Means
Less than 20 grams of fiber per day
Your score is pretty typical for most modern industrialized nations, but it’s not doing your health any favors.
With less than 20 grams of fiber per day, you may be hungry often and have trouble with constipation and other digestive issues. At this level, the risk for certain chronic diseases, including heart disease and some forms of cancer, is also increased.
But the good news is, it’s easy to change all this by incorporating more fiber-rich foods into your diet!
20–39 grams of fiber per day
You’re getting more than many people eating the standard American diet, but you may still have room for improvement.
Focus on crowding out foods that contain little to no fiber by adding more fiber superstars to your meals — like beans and lentils. By doing so, you’ll probably find that you feel more satisfied and that maintaining a healthy weight becomes easier. Plus, you’ll further reduce your risk of chronic diseases and early mortality.
40+ grams of fiber per day
Your diet is loaded with fiber-rich whole plant foods. You’re in the tiny fraction of the population that is actually getting PCRM’s recommended amount of fiber. Way to go!
A Fiber-Rich Meal Plan
What does high-fiber eating look like?
If most people eat less than the recommended amount of fiber per day, you may be thinking, “How am I going to eat 40 or more grams of fiber (or even 28 grams) per day?”
It’s easier than you think. Here’s what a typical day might look like:
Breakfast: Buckwheat Chia Pancakes: 13 grams from the buckwheat + 2 grams from the chia + 1 gram from the mashed banana = 16 grams
Lunch: Avocado Salad: 4 ½ grams from the avocado + 4 grams from the black beans + 2 grams from the arugula, tomato, onion and cilantro = 10.5 grams
Snack: Moroccan Baked Chickpeas: = 7 grams
Dinner: Vegan Mince Lettuce Tacos: 6 grams from the lentils + 3 grams from the veggies, including romaine lettuce shells = 9 grams
Total Fiber: 42.5 (Ding ding ding, we have a winner!)
Take Action for Your Health: Fiber Challenge
Now that you know why fiber is so good for you and how to get enough fiber in your diet, team up with a friend or family member and challenge yourself and each other to reach 40 grams of fiber per day consistently.
If you’re new to eating a lot of fiber, be sure to add it to your diet slowly, because increasing your fiber intake too quickly can cause bloating and gas or other negative side effects. It’s also important to drink plenty of water while increasing your consumption of fiber-rich foods. When you increase gradually and allow your body to become used to the increase in fiber, you probably won’t experience any discomfort.
Fiber may be the least glamorous nutrient in the conversation about healthy eating. No one (except maybe yours truly!) is writing breathless headlines about their high-fiber diet. But the evidence is hard to argue with. Better digestion, lower cancer risk, a healthier heart, steadier blood sugar, and a longer life. All from eating more plants. Take the 40-gram challenge, add it gradually, drink plenty of water, and see how you feel. The results might surprise you.
Tell us in the comments:
- Do you get enough fiber?
- What’s one simple change can you make today to start incorporating more fiber into your diet?
- What benefits have you noticed from adding more fiber to your diet?
Featured Image: iStock.com/apomares
