Advantages and disadvantages of a high-fiber diet

In my last blog article the advantages and disadvantages of a low-carb ketodiet versus a low-fat diet were discussed, but I also briefly touched the tactics of a cycling team to lower fiber intake before and during difficult mountain stages, so that even the content of their intestines would be minimized.

We won't touch upon reasons to lower fiber intake for optimal performance but instead focus on reasons to embrace a high-fiber diet and try to examine when fiber intake may be too high.

What is the definition of fiber?

Fiber is a type of carbohydrate that the body can’t digest. Though most carbohydrates are broken down into sugar molecules called glucose, fiber cannot be broken down into sugar molecules, and instead it passes through the body undigested. Fiber helps regulate the body’s use of sugars, helping to keep hunger and blood sugar in check.

Children and adults need at least 25 to 35 grams of fiber per day for good health, but most people get only about 15 grams a day. Great sources are whole grains, whole fruits and vegetables, legumes, and nuts.

Fiber comes in two varieties, both beneficial to health:

Soluble fiber, which dissolves in water, can help lower glucose levels as well as help lower blood cholesterol. Foods with soluble fiber include oatmeal, chia seeds, nuts, beans, lentils, apples, and blueberries.

Insoluble fiber, which does not dissolve in water, can help food move through your digestive system, promoting regularity and helping prevent constipation. Foods with insoluble fibers include whole wheat products (especially wheat bran), quinoa, brown rice, legumes, leafy greens like kale, almonds, walnuts, seeds, and fruits with edible skins like pears and apples.

Further defining fiber
Under the umbrella terms of insoluble and soluble fibers, you may see fiber described in other ways. It can be viscous with a gel-like quality, or fermentable because it acts as food for gut bacteria that break down and ferment it. Fibers that are not broken down by bacteria, called nonfermentable, travel intact to the colon and can add bulk and weight to stool so it is easier to pass. These properties offer health benefits such as slowing down digestion, delaying blood sugar rises after meals, promoting healthy colonies of bacteria, or having a laxative effect. In addition, there are many subtypes of soluble and insoluble fibers, some of which occur naturally in plant foods and others that are synthetically made.

Fiber is defined by the National Academy of Medicine as:
1) dietary fibers (nondigestible carbohydrates and lignans) that occur naturally in plants, and
2) functional fibers that are extracted from plants or synthetically made and are nondigestible with a beneficial health effect in humans.
Some types of fiber fall into both categories, such as oligosaccharides and resistant starches that may be naturally occurring or synthetically made.

Naturally occurring plant fibers

Cellulose, hemicellulose: insoluble fiber found in cereal grains and the cell walls of many fruits and vegetables. It absorbs water and adds bulk to stool, which can have a laxative effect.

Lignans: insoluble fiber found in wheat and corn bran, nuts, flaxseeds, vegetables, and unripe bananas that triggers mucus secretion in the colon and adds bulk to stools. Has laxative effect.

Beta-glucans: soluble highly fermentable fiber found in oats and barley that is metabolized and fermented in the small intestine. Acts as a prebiotic. Can add bulk to stool but does not have a laxative effect. May help to normalize blood glucose and cholesterol levels.

Guar gum: soluble fermentable fiber isolated from seeds. Has a viscous gel texture and is often added to foods as a thickener. It is metabolized and fermented in the small intestine. Does not have a laxative effect. May help to normalize blood sugar and cholesterol levels.

Inulin, oligofructose, oligosaccharides, fructooligosaccharides : soluble fermentable fibers found in onions, chicory root, asparagus, and Jerusalem artichokes. May help to bulk stool with a laxative effect, normalize blood glucose, and act as a prebiotic. People with irritable bowel syndrome may be sensitive to these fibers that can cause bloating or stomach upset.

Pectins: soluble highly fermentable fiber found in apples, berries, and other fruits. Minimal bulking or laxative effect. Due to its gelling properties, it may slow digestion and help normalize blood sugar and cholesterol levels.

Resistant starch : soluble fermentable fiber found in legumes, unripe bananas, cooked and cooled pasta, and potatoes that acts as a prebiotic. Adds bulk to stools but has minimal laxative effect. May help to normalize blood sugar and cholesterol levels.

Manufactured functional fibers, some of which are extracted and modified from natural plants

Psyllium: soluble viscous nonfermentable fiber extracted from psyllium seeds that holds onto water and softens and bulks stools. Has laxative effect and is an ingredient in over-the-counter laxatives and high-fiber cereals. May help to normalize blood sugar and cholesterol levels.

Polydextrose and polyols: soluble fiber made of glucose and sorbitol, a sugar alcohol. It can increase stool bulk and have a mild laxative effect. Minimal effect on blood sugar or cholesterol levels. It is a food additive used as a sweetener, to improve texture, maintain moisture, or to increase fiber content.

Inulin, oligosaccharides, pectins, resistant starch, gums : soluble fibers derived from plant foods as listed above, but are isolated or modified into a concentrated form that is added to foods or fiber supplements.

Fiber and disease

Fiber appears to lower the risk of developing various conditions, including heart disease, diabetes, diverticular disease, and constipation. Fiber’s beneficial role in the gut microbiome may produce anti-inflammatory effects that alleviate the chronic inflammation associated with these conditions: heart disease, type 2 diabetes, breast cancer, colorectal cancer, constipation, diverticular disease


Fiber helps with weight loss
Dietary fiber helps promote weight loss because it's filling while also being low in calories. And when you eat more high-fiber foods, you have less room in your diet for foods that are not as nutrient-dense, such as refined carbohydrates.
Fibrous foods can also be a good source of lean protein, instead of higher-fat sources like red meat. One study published in 2015 found that simply focusing on adding more fiber to your diet can lead to weight loss almost as effectively as following a strict diet.

Fiber may reduce risk of cancer
A 2016 review of studies found that dietary fiber lowers the risk of cancer death as well. In particular, the improved digestion associated with dietary fiber may help reduce the risk of colon cancer.

Fiber lowers blood sugar
High fiber intake can also reduce blood sugar levels, which is important for those with diabetes. Research shows that a fiber-rich diet can both prevent and help treat type 2 diabetes.

A high-fiber diet is sustainable
Following a high-fiber diet is safe and healthy to continue for the long term.

Disadvantages of a high-fiber diet

Without any formal guidelines to follow, some people may not understand how to boost their fiber intake while also eating healthfully. A high-fiber diet can be a healthy choice when it includes a variety of nutritious foods. Following a high-fiber diet while also consuming too many processed foods and added sugars is not a balanced approach to health.
A high-fiber diet may cause some discomfort at first, but you may find that the downsides are relatively minor and can be overcome.

Fiber may lead to intestinal gas
High-fiber foods, especially beans, have a reputation. Yes, it's true that they can cause or worsen intestinal gas. It may be embarrassing, but it's harmless and a sign that the good bacteria in the gut are doing their job. And prebiotic fiber can actually help make that gas less smelly.

Consuming more fiber than your body can handle may cause gas, bloating, abdominal pain, loose stools or diarrhea, and even constipation. While these symptoms are typically mild, some people may experience more intestinal discomfort than others.

Fiber could contribute to abdominal bloating
Both gas and bloating are a result of consuming too much fiber, too fast. So if you plan to start a high-fiber diet, do it gradually. Add fiber a little bit at a time so that your digestive system can handle it.

Fiber may not be the best choice for people suffering from gastrointestinal disorders
Those with certain gastrointestinal conditions like irritable bowel syndrome (IBS) may experience worsened symptoms with excessive fiber intake.

Fiber is high in FODMAPs
Some foods that are high in fiber are also high in FODMAPs, a group of carbohydrates that can cause symptoms in people with certain bowel diseases.

Fiber requires a learning curve
Most people aren't getting enough fiber in their current diet. So some people may find that cooking with high-fiber foods is unfamiliar territory and takes time to learn.

Fibers may reduce nutrient absorption
Excessive fiber intake can interfere with the absorption of certain minerals, such as calcium, iron, magnesium, and zinc. This can be of concern, especially for individuals with nutrient deficiencies.

Fiber intake may lead to dehydration
High-fiber diets require increased water intake to prevent constipation. If you don’t drink enough water, excessive fiber intake can make constipation worse.

Fiber may lead to excessive weight loss or malnutrition
In extreme cases, very high-fiber diets may lead to unintended weight loss or malnutrition, as they can reduce overall calorie intake and nutrient absorption.

How can I relieve symptoms of too much fiber?

If you ate too much fiber and are experiencing the symptoms of too much intake, try the following to help counteract the effects:
Drink plenty of water.
Stop using any fiber supplements.
Avoid high-fiber foods.
Eat a bland diet.
Remove fiber-fortified foods from your diet.
Look for foods that contain substances such as inulin and chicory root extract.
Engage in light physical activities, like walking, as often as possible.
Consider keeping an online diary of your food intake to help you see how much fiber you’re getting each day.
Consider following a low FODMAP diet if you have irritable bowel syndrome (IBS). This temporary diet can improve symptoms by removing fermentable, fibrous foods from your diet.

Once you start feeling better, you should slowly re-introduce fiber-rich foods into your diet. Instead of eating fiber-rich foods in one meal, spread them out throughout the day. It’s best to get your fiber from a variety of foods, so don’t rely on any one food or source. Aim for a wide range of fruits, vegetables, whole grains, beans, and nuts.

Side effects of fiber deficiency

A deficiency of dietary fiber in your daily diet can have several adverse effects on your health and well-being:

Digestive issues
Insufficient fiber can lead to constipation, as fiber adds bulk to stool and facilitates regular bowel movements. Chronic constipation can cause discomfort and potentially lead to more severe gastrointestinal problems.

Weight gain
Fiber helps control appetite by promoting a feeling of fullness. A lack of fiber can contribute to overeating, weight gain, and obesity.

Blood sugar spikes
Fiber plays a role in stabilizing blood sugar levels. Without enough fiber, you may experience rapid spikes and crashes in blood sugar, which can increase the risk of type 2 diabetes.

Poor cardiovascular health
A low-fiber diet can result in higher cholesterol levels and an increased risk of heart disease. Soluble fiber, in particular, helps lower LDL (bad) cholesterol.

Colon health problems
Insufficient fiber intake may increase the risk of colorectal cancer. fiber aids in moving waste through the colon and may reduce exposure to harmful substances.

Hunger and cravings
Low-fiber diets can lead to persistent feelings of hunger and cravings for unhealthy, high-calorie foods.

Gut imbalance
Fiber is a crucial source of nutrition for beneficial gut bacteria. A lack of fiber can disrupt the balance of your gut microbiome, potentially impacting your overall health.

To maintain optimal health, it’s essential to include an adequate amount of fiber in your daily diet. Aim for a variety of fiber-rich foods such as fruits, vegetables, whole grains, legumes, nuts, and seeds to ensure you reap the many health benefits associated with fiber consumption.

Daily fiber requirements

Daily fiber requirements vary based on age and individual needs. Here are general guidelines for different age groups:

Children (4 to 14 years old): children should aim for about 25-30 grams of fiber per day.
Teenagers (14 to 18 years old): teen girls should get about 25 grams of fiber per day, and teen guys should get about 31 grams of fiber per day.
Adults (19-50 years old): adults should aim for 25-38 grams of fiber daily, depending on individual needs and activity levels.
Older adults (51 years and older): older adults should continue aiming for 25-38 grams of fiber daily, as fiber remains essential for digestive health and overall well-being.

Is the high-fiber diet a healthy choice?

A high-fiber diet abundant in whole grains, vegetables, fruits, and legumes is closely aligned with current dietary guidelines for a healthy, balanced diet. It is also recommended to consume more fiber to meet recommended daily intake which is rarely met.

Consuming more fiber-rich foods has several health benefits, including helping with weight loss. A diet high in fiber that also encourages a variety of nutrient-dense foods adheres to federal guidelines for a well-balanced diet.

Summary

There are many types of dietary fibers that come from a range of plant foods. It’s important to not hyperfocus on a particular fiber because of its specific proposed action, as each type offers some level of health benefit. Therefore, eating a wide variety of plant foods like fruits, vegetables, whole grains, legumes, nuts, and seeds to reach the fiber recommendation of 25-35 grams daily best ensures reaping those benefits.

The evidence is convincing: Adding more fiber to your diet is a smart way to improve your health and, most likely, lose weight. Just use caution if you have any digestive health concerns or inflammatory bowel disease, and always add fiber to your diet gradually instead of all at once. If you do have a health condition and are interested in learning how you might benefit from a high-fiber diet, consult your healthcare provider for more advice.

Remember, following a long-term or short-term diet may not be necessary for you and many diets out there simply don’t work, especially long-term. While we do not endorse fad diet trends or unsustainable weight loss methods, we present the facts so you can make an informed decision that works best for your nutritional needs, genetic blueprint, budget, and goals.

If your goal is weight loss, remember that losing weight isn’t necessarily the same as being your healthiest self, and there are many other ways to pursue health. Exercise, sleep, and other lifestyle factors also play a major role in your overall health. The best diet is always the one that is balanced and fits your lifestyle.