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6 Signs of Fiber Deficiency

Fiber is crucial for keeping the gut healthy, and a healthy gut is particularly important for athletes. That means a fiber deficiency may negatively affect your sports performance —  so how do you know if you’re getting enough fiber? 

What is fiber?

Fiber is a type of indigestible carbohydrate. Most carbohydrates are broken down into sugar molecules, but fiber passes through your body without being digested. Fiber is what helps regulate the body’s use of sugars, reduces the risk of developing cardiovascular disease and keeps your hunger and blood sugar levels in check. 


There are two kinds of dietary fiber: soluble fiber and insoluble fiber. Soluble fiber dissolves in water, while insoluble fiber does not. When dissolved, soluble fiber forms a thick gel-like substance in the stomach. It is broken down by bacteria in the large intestine. Soluble fiber is what helps lower blood cholesterol and glucose levels. Insoluble fiber does not dissolve; instead, it passes through the gastrointestinal tract relatively intact. This type of fiber helps food move efficiently through your digestive system, promotes bowel regularity and prevents constipation.


As mentioned above, fiber is necessary for your gut and digestive health. For athletic purposes, your gut and digestive health are foundational building blocks of a high-performance lifestyle. Think about it: No one wants to work out feeling bloated or uncomfortably full. These feelings can get in the way of your workout, but fiber helps counteract this effect.   


An increase in soluble fiber is linked to blood glucose stabilization. The short chain fatty acids making up fiber also directly affect glycogen release in the liver. The glycogen stores in the liver account for around 14% of the body’s available energy stores. This means that getting proper amounts of fiber leads to more consistent energy supply — key for top performance. 

How much fiber do you need per day?

According to the Food and Drug Administration, the Daily Value for fiber is 28 grams per day, or about 14 grams per 1000 calories. According to the Centers for Disease Control and Prevention’s 2015-2016 National Health and Nutrition Examination Survey, most Americans only eat about half the daily recommended amount; in fact, 95% of Americans never meet the recommended intake level. For optimal performance, you should aim to meet the Daily Value and get around 28 grams of fiber per day, though factors such as disease risk should be taken in consideration when figuring out recommended intake.


Not only does getting proper amounts of fiber help your sports performance, the Cleveland Clinic notes that people who eat between 25-29 grams of fiber per day also see a 15-30% decrease in their risk of colon cancer, as well as the risk of developing heart disease and diabetes.

High fiber foods: Which foods contain fiber in high amounts?

There are tons of foods that are naturally high in fiber. You can find soluble fiber in foods like nuts, lentils, oatmeal, beans, peas, apples, pears and berries. Insoluble fiber is found in foods like whole wheat bread, brown rice, wheat bran, legumes, carrots, cucumbers and tomatoes.


While fiber is found naturally in foods like whole grains, starches, fruits, vegetables, legumes and nuts, it’s also commonly added to snack foods like cookies and granola bars. Chances are, you’ve probably seen a box of cereal advertising “great source of fiber!” despite the fact that this type of food actually contains little to no fiber naturally. The fiber in these types of snack products are usually isolated fibers that are synthetically made using chemicals. 


What’s the point of adding fiber to these foods? As you know, the Daily Value for dietary fiber is 28 grams per day, but most Americans only get about 16 grams per day, per the U.S. National Library of Medicine. Companies know that fiber is part of a gut-healthy diet, so they add fiber to appeal to nutrient-conscious consumers. 


However, you don’t have to only get fiber from foods — sports nutrition companies like Gainful offer fiber supplements. Gainful’s Fiber Performance Boost includes a scientist-recommended dosage of beta glucan, which is a heart-healthy soluble fiber that is derived from oat fiber. This type of fiber serves as food for the probiotics that maintain healthy balances of bacteria. 


The Fiber Performance Boost rounds out a complete nutrition system, so athletes can get the nutrients they need to make the most of their workouts. You can start by taking Gainful’s quiz. From there, a team of experts will review your answers and recommend formulas based on your body and your life. You’ll receive a customized Protein Powder blend, Pre-Workout and Hydration Formula, as well as recommendations for Performance Boosts. Gainful protein powder blends include 1 gram of fiber (5% DV), but for added fiber intake, you can add Gainful’s Fiber Performance Boost. The Fiber Performance Boost is able to help provide additional nutrient absorption and satiation, which allows you to reach your fitness goals faster and more efficiently. Individuals who are limiting whole grains in their diet may experience B vitamin losses and fiber losses, so Gainful’s Fiber Performance Boost can also help make up for the lack of fiber. You can also blend your personalized protein powder with frozen fruits, vegetables or oats for a delicious way to get extra fiber and nutrients from whole foods. 


Your Fiber Performance Boost is flexibly dosed based on your quiz answers and can be easily added onto your next Gainful order. From the Fiber Performance Boost to the protein powders, pre-workout and hydration formulas, each Gainful product contains science-backed ingredients that are added specifically for your needs, serving as a testament to Gainful’s commitment to personalization. 

What happens if you don’t have enough fiber in your diet? Fiber deficiency and its side effects

Not getting enough fiber in your diet leads to fiber deficiency. Fiber helps support your gut and microbiome health, so if you don’t get enough fiber, you may experience irregular bowel movement, constipation, blood sugar fluctuations, lack of satiety after eating or a rise in cholesterol levels. There are a number of microorganisms that reside in our gut that are integral to maintaining a healthy immune system, and fiber is what feeds these microorganisms and allows them to do their job. Without proper amounts of fiber, the health of your immune system may also be compromised. 


Failing to meet daily fiber intake recommendations may also affect your mood and cognition. When levels of healthy bacteria in the gut are stabilized, the risk of mental health disorders such as depression are lowered. Fiber helps improve mood and cognition through the “second brain,” which refers to the nerves in the intestine that communicate with the brain. 

Fiber deficiency symptoms

There are six main signs of fiber deficiency:

If you experience any of these symptoms, you may want to track your fiber intake. Once you increase your fiber intake, keep tabs on whether any of these symptoms go away. If they disappear or are alleviated, that might mean you were experiencing a fiber deficiency and needed more fiber-rich foods in your diet. 

Diseases associated with fiber deficiency

It’s clear that fiber plays an important role in your overall health; in fact, many experts believe fiber deficiency is the link that connects a number of diseases. The Burkitt’s hypothesis — named after Denis Burkitt, a surgeon who rigorously studied the role of fiber in human health — is the idea that diets low in fiber increase the risk of coronary heart disease, obesity, diabetes, cavities, various vascular disorders and large bowel conditions such as cancer, appendicitis and diverticulosis. Burkitt grouped these diseases together based on having the same cause: lack of fiber, or a low-fiber diet. He followed Cleave’s common cause hypothesis, which suggests that if a group of diseases occur together in the same population or individual, they are likely to have a common cause. Per a 2017 article titled “Denis Burkitt and the origins of the dietary fibre hypothesis” published in the journal Nutrition Research Reviews, simply grouping these diseases together as having a common cause was groundbreaking (though proposing fiber as the key factor in these diseases stimulated controversy among experts at the time, who felt this hypothesis needed significantly more research). 


Since Burkitt’s death in 1993, Burkitt’s hypothesis has been verified by large-scale epidemiological studies. According to a 2020 article titled “The association between dietary fibre deficiency and high-income lifestyle-associated diseases: Burkitt’s hypothesis revisited” published in the journal The Lancet Gastroenterology & Hepatology, researchers have reported that fiber deficiency does increase the risk of heart disease and the risk of colon, liver and breast cancers. Serious fiber deficiency also reportedly increases cancer mortality and death from cardiovascular, infectious, and respiratory diseases, diabetes and all non-cardiovascular, non-cancer causes. These researchers believe that increasing dietary fiber intake to as much as 50 grams per day and consuming more fiber-rich foods will increase lifespan, improve the quality of life during the added years and substantially reduce health-care costs.

Answering your fiber Qs

Still have a few lingering questions about fiber? Don’t forget: As part of your Gainful subscription, you always have a Registered Dietitian on-hand who’s there to answer any questions or concerns regarding fiber, your protein powder or anything else related to your fitness, diet and wellness goals. 


Take the quiz to get your personalized protein powder, access to your own R.D. and add Gainful’s Fiber Performance Boost to your subscription.