What is another term for dietary fiber?

December 24, 2025 •

4 min read

According to the U.S. Dietary Guidelines, most Americans consume less than half of the recommended daily amount of fiber. Addressing this nutritional gap often starts with understanding the basics, such as answering the question: what is another term for dietary fiber?

Quick Summary

Several terms are used interchangeably with dietary fiber, such as roughage and bulk, referring to the indigestible part of plant-based foods that promotes digestive health. The article examines the different terminologies and the distinct roles of soluble and insoluble fiber.

Key Points

Roughage: A common and traditional term for dietary fiber, emphasizing its fibrous texture and ability to add bulk to stool.
Bulk: Another frequently used term, describing fiber's capacity to absorb water and increase the volume of digestive contents.
Non-Starch Polysaccharides (NSP): A technical term used in scientific contexts to refer to specific types of fiber that cannot be digested by human enzymes.
Two main types: Dietary fiber is primarily categorized into soluble fiber (forming a gel) and insoluble fiber (adding bulk), each with distinct health benefits.
Extensive health benefits: Beyond digestion, fiber helps lower cholesterol, control blood sugar, manage weight, and support a healthy gut microbiome.
Spelling variations: The term can also be spelled as "fibre" in countries following British English.
Increase intake gradually: To avoid digestive discomfort, it's best to increase fiber intake slowly and ensure you drink plenty of water.

Common Terms for Dietary Fiber

While "dietary fiber" is the most scientifically accurate and commonly understood term, other names are frequently used in both casual conversation and on food labels. These alternative names often describe the physical function of fiber within the digestive system.

Roughage

One of the most traditional terms for dietary fiber is "roughage". This name derives from the fibrous or 'rough' texture of many high-fiber foods, such as raw vegetables and whole grains. The term highlights the indigestible plant material's role in providing bulk to stool, which helps stimulate the digestive tract and promote regularity.

Bulk

Another simple and descriptive alternative is "bulk" or "bulking agent". This term emphasizes fiber's ability to absorb water and add volume to the contents of the digestive system. This action is crucial for a healthy digestive process, as it aids in moving waste through the intestines more efficiently. Psyllium husk, for instance, is often referred to as a bulking fiber.

Non-Starch Polysaccharides (NSP)

From a technical perspective, "non-starch polysaccharides" is another, more specific term for certain types of dietary fiber. As the name suggests, this category includes plant carbohydrates that are not starch and cannot be digested by human enzymes. The term is sometimes used in scientific literature and nutritional analyses to define the specific components of fiber.

Fibre (UK spelling)

It is also worth noting that in British English and many other English-speaking countries, the word is spelled "fibre" instead of the American "fiber". While not a different term, this spelling variation is a notable difference to be aware of when reading nutrition information from different regions.

Soluble vs. Insoluble: Two Major Categories of Fiber

To fully appreciate what is another term for dietary fiber, it is vital to understand its two primary forms, each with unique functions and sources.


Feature	Soluble Fiber	Insoluble Fiber
Primary Function	Forms a gel-like substance in water, slowing digestion.	Adds bulk to stool, speeding up waste transit.
Main Benefit	Helps lower cholesterol and control blood sugar levels.	Prevents constipation and promotes regularity.
Fermentability	Is fermented by bacteria in the large intestine.	Generally not fermented, or only partially.
Sources	Oats, barley, nuts, seeds, legumes, apples, and citrus fruits.	Whole grains, wheat bran, vegetables (e.g., green beans, cauliflower), and potato skins.

The Health Benefits Beyond Digestion

While the primary functions of roughage and bulk focus on digestive health, the benefits of dietary fiber extend far beyond simply promoting regularity. Regular intake of fiber is linked to a reduced risk of several chronic diseases.

Cardiovascular Health

Consuming soluble fiber is particularly effective at lowering LDL ("bad") cholesterol levels. The gel-like consistency of soluble fiber traps bile acids and cholesterol in the digestive tract, preventing them from being reabsorbed and forcing the body to use stored cholesterol to create more bile, which helps lower overall blood cholesterol.

Blood Sugar Control

For individuals with diabetes, consuming adequate amounts of fiber is critical. Fiber, especially soluble fiber, slows down the absorption of sugar into the bloodstream, which helps to prevent rapid spikes in blood glucose and insulin levels. This stabilizing effect is vital for maintaining healthy blood sugar levels over time.

Weight Management

High-fiber foods generally have a lower energy density, meaning they provide fewer calories for the same volume of food compared to low-fiber foods. Furthermore, because fiber adds bulk and slows digestion, it helps you feel full for longer, which can help manage calorie intake and support weight control efforts.

Gut Microbiome Health

Certain types of fiber, including soluble and fermentable varieties, serve as prebiotics. This means they are food for the beneficial bacteria in your gut microbiome. When these gut bacteria ferment fiber, they produce short-chain fatty acids (SCFAs), which have numerous health benefits, including reducing inflammation and improving the health of the intestinal lining.

Cancer Prevention

Multiple studies have shown an association between high fiber intake and a reduced risk of certain types of cancer, especially colorectal cancer. The bulk and faster transit time of insoluble fiber help dilute potential carcinogens and move them out of the body more quickly. Additionally, the SCFAs produced from fiber fermentation may have protective effects against cancer development.

How to Increase Your Dietary Fiber Intake

Increasing fiber intake does not require drastic dietary changes. Small adjustments can make a significant difference. Here are some simple steps:

Embrace Whole Grains: Choose whole-wheat bread, brown rice, and oatmeal over refined options.
Add Legumes: Incorporate beans, lentils, and peas into soups, salads, and stews.
Focus on Fruits and Vegetables: Eat fruits with the skin on and add extra vegetables to your meals.
Snack Smart: Replace low-fiber snacks with nuts, seeds, or whole-grain crackers.
Hydrate: Drink plenty of water. Without adequate fluid, high fiber can sometimes lead to constipation, rather than relieving it.

Conclusion

The simple answer to "what is another term for dietary fiber?" reveals a lot about its vital functions. Synonyms like roughage, bulk, and non-starch polysaccharides (NSP) offer different perspectives on fiber's role, from its physical texture to its chemical composition. Ultimately, understanding these terms underscores the importance of a fiber-rich diet, which is essential for maintaining not only a healthy digestive system but also for supporting overall well-being, from heart health to weight management.

Resources for Further Reading

For more detailed information on dietary fiber and its health benefits, visit the MedlinePlus resource: Dietary Fiber - MedlinePlus.

Frequently Asked Questions

The most common and traditional synonym for dietary fiber is "roughage". Another frequently used term is "bulk" or "bulking agent".

Fiber is called 'bulk' because it has the ability to absorb water and increase the volume of stool, which helps to move waste through the digestive system more easily and efficiently.

Soluble fiber dissolves in water to form a gel-like material and helps lower cholesterol and glucose levels, while insoluble fiber does not dissolve and adds bulk to stool, promoting regular bowel movements.

While roughage is a common synonym, it more accurately describes insoluble fiber, which has a fibrous texture. Soluble fibers, which form a gel, are not physically rough.

'Non-starch polysaccharides' is a scientific term that refers to certain types of dietary fiber, specifically the plant carbohydrates that resist human digestive enzymes. It is a more technical name for a component of fiber.

Good sources of roughage (insoluble fiber) include whole grains like wheat bran, vegetables such as green beans and cauliflower, and the skins of fruits and potatoes.

A bulking agent is a substance, like fiber, that adds volume and mass to the digestive tract. Some fiber supplements, such as psyllium, are specifically used as bulking agents.

Yes, in a general context, you can use these terms interchangeably. However, dietary fiber is the more precise and comprehensive term, as roughage tends to emphasize the coarse, indigestible aspect of fiber.