Vegetables and fruits are two major sources of dietary fiber. However, not all fruits and vegetables have high fiber content. Even with large quantities consumed, it can be challenging to meet the daily recommended intake. This discussion will focus on how to incorporate dietary fiber into your diet and explore hidden sources of high-fiber foods. By appropriately supplementing your diet, you can easily achieve the recommended daily fiber intake.
Inadequate Dietary Fiber Intake Among the Population Due to Food Choices
As health awareness increases and dietary habits change with an emphasis on consuming more vegetables and fruits, many individuals may feel confident about their daily fiber intake. However, it was found that most of people had dietary fiber intake levels below the recommended daily intake. The reason for this shortfall might lie in food choices.
While vegetables and fruits are generally considered good sources of dietary fiber, it’s important to note that some of them have relatively low fiber content. Even with substantial consumption, it can be challenging to meet the recommended daily intake. Therefore, this discussion will primarily address how to incorporate dietary fiber into your diet. Additionally, we’ll explore other hidden sources of high-fiber foods, making it easier to achieve the recommended daily fiber intake.
What Is High-Fiber?
High-fiber foods contain a higher amount of dietary fiber. Dietary fiber refers to carbohydrates that cannot be broken down by enzymes in the human small intestine (with a monomer count > 3) or lignin. The composition of carbohydrates (glucose, fructose, galacturonic acid, etc.) or their degree of polymerization (oligosaccharides or polysaccharides) determines their various arrangements.
Common examples of carbohydrate polymer fibers include cellulose made up of glucose units, pectin composed of galacturonic acid units, and fructooligosaccharides formed from fructose units.
Dietary fiber is classified in various ways, one of which is based on its solubility in water. It’s divided into soluble and insoluble dietary fiber. Common soluble fibers include pectin, gums, oligosaccharides, and hemicellulose. Insoluble fibers include cellulose, hemicellulose, lignin, and chitin[1].
A food can be considered “high-fiber” if it contains over 3 grams of dietary fiber per 100 grams. For packaged solid products, regulations require at least 6 grams of dietary fiber per 100 grams for them to be labeled as “high-fiber.”
Benefits of High-Fiber Foods
1. Weight Management
After fermentation by colonic bacteria, water-soluble dietary fiber can increase the secretion of two appetite-regulating hormones, glucagon-like peptide (GLP-1) and peptide YY, reducing appetite. Additionally, water-soluble dietary fiber has a gelling effect with higher viscosity, which can extend gastric emptying time, increase satiety, and decrease food intake, thus aiding in weight management[3].
2. Gastrointestinal Health
Certain dietary fibers can serve as prebiotics, providing the necessary nutrients for the growth of beneficial gut bacteria while indirectly inhibiting the growth of harmful bacteria.
Only a portion of non-water-soluble dietary fiber is fermented by colonic bacteria, and due to its excellent water-holding capacity, it can increase stool volume, stimulate bowel movements, shorten transit time, and reduce contact time between harmful substances and the intestinal wall.
Water-soluble dietary fiber, aside from its water-holding properties, has a gel-like characteristic that lubricates feces, facilitating smooth passage through the intestines. Most water-soluble fibers and some non-water-soluble fibers can be fermented by colonic bacteria to produce short-chain fatty acids (SCFA). SCFA are proven to serve as a colon energy source, reduce the production of inflammatory cytokines, and maintain intestinal integrity[4].
3. Cardiovascular Protection
Both water-soluble and non-water-soluble dietary fiber can reduce the absorption of dietary cholesterol.
Water-soluble dietary fiber promotes bile acid excretion, reducing cholesterol due to the need for replenishing lost bile acids. SCFA, fermentation products of dietary fiber, inhibit a key enzyme in cholesterol synthesis, HMG CoA reductase, leading to decreased endogenous cholesterol synthesis.
Dietary fiber can lower the production of pro-inflammatory substances in the body, such as C-reactive protein and interleukins.Overall, increasing dietary fiber intake, especially water-soluble fiber with gelling properties, can lower the incidence and mortality rate of cardiovascular diseases[5].
4. Blood Sugar Control
Viscous water-soluble dietary fiber can delay gastric emptying, reduce nutrient digestion, and slow down carbohydrate absorption, leading to stabilized postprandial blood sugar levels.
Fermentation products of dietary fiber, such as SCFA, can stimulate insulin secretion by increasing the concentration of glucagon-like peptide GLP-1. Dietary fiber from whole grains is particularly effective in preventing the development of type 2 diabetes. Epidemiological studies have observed positive effects of increased dietary fiber supplementation on fasting blood sugar and glycated hemoglobin levels in type 2 diabetes patients[6].
What are High-Fiber Vegetables and Fruits?
When considering edible portions per 100 grams, dried foods typically have a higher fiber content compared to fresh foods. Below are some examples of high-fiber vegetables, fruits, and various types of foods listed separately[7].
High-Fiber Vegetables
| Edible parts per 100g | |||||
| TOP | Name | Dietary fiber content (g) | TOP | Name | Dietary fiber content (g) |
| 1 | Laver | 29 | 1 | Tremella | 5.1 |
| 2 | Red Moss | 26.6 | 2 | burdock | 5.1 |
| 3 | Prunes | 12.8 | 3 | Kelp stalk | 4.4 |
| 4 | Basil | 8.8 | 4 | garlic | 4.2 |
| 5 | Agaric | 7.4 | 5 | Yellow Carrot | 4.1 |
| 6 | Dried radish | 7.2 | 6 | Wild bitter melon | 4.1 |
| 7 | Wakame | 6.1 | 7 | Purple wild vegetables | 3.9 |
| 8 | Toon | 5.9 | 8 | okra | 3.7 |
| 9 | Xiu canned mushrooms | 5.6 | 9 | Bitter melon (green skin) | 3.6 |
| 10 | Mushroom | 5.4 | 10 | Nine-story Pagoda | 3.4 |
High-Fiber Fruits
| per 100g edible portion | ||
| TOP | Name | Dietary fiber content (g) |
| 1 | persimmon | 12.6 |
| 2 | Red dates | 7.7 |
| 3 | Avocado | 5.7 |
| 4 | passion fruit | 5.3 |
| 5 | Guava | 5 |
| 6 | An Pomegranate | 4.6 |
| 7 | Surrounded Persimmon | 4.4 |
| 8 | Red Heart Guava | 3.9 |
| 9 | Taiwan jujube | 3.9 |
| 10 | Canna | 3.3 |
| 11 | Long fruit kumquat | 3.2 |
| 12 | Durian | 3.2 |
| 13 | Fushou peach | 3.1 |
| 14 | Dried longan | 2.9 |
| 15 | Kiwi | 2.7 |
Ranking of High-Fiber Foods
| per 100g edible portion | |||||
| TOP | Name | Dietary fiber content (g) | TOP | Name | Dietary fiber content (g) |
| 1 | Mountain noodles | 57.9 | 1 | Salted Crispy Broad Beans | 23.1 |
| 2 | Anchovy | 43.1 | 2 | Big red beans | 20.5 |
| 3 | Orange peel | 39.5 | 3 | Licorice sunflower seeds | 19.7 |
| 4 | Cooked seaweed | 37.3 | 4 | Food beans | 19.3 |
| 5 | Hawthorn | 36.5 | 5 | Dried bamboo shoots | 17 |
| 6 | Chia | 29.7 | 6 | Dehydrated kale | 17 |
| 7 | Roasted black beans | 27.1 | 7 | Mung beans | 15.8 |
| 8 | Sushi seaweed slices | 26.5 | 8 | Rice Germ | 14.7 |
| 9 | Fried Dehydrated Sweet Potato | 25 | 9 | Dark Chocolate (85%) | 14.2 |
| 10 | Linseed | 23.1 | 10 | Black sesame (hot) | 14 |
What to Consider When Consuming High-Fiber Foods?
The principle of supplementing dietary fiber should involve a gradual and progressive increase. If an excessive amount of fiber is consumed in a short period of time, it can lead to gastrointestinal symptoms such as bloating, diarrhea, or abdominal pain.
Additionally, when increasing dietary fiber intake, it’s important to remember to hydrate adequately. Dietary fiber has good water-holding capacity, and insufficient fluid intake can lead to drier stools, exacerbating constipation. In certain situations where it’s necessary to reduce stool volume or gastrointestinal load, fiber intake should be lowered. This is the case for severe diarrhea, gastroenteritis, acute flare-ups of ulcerative colitis, diverticulitis, and intestinal obstruction.
In this presentation, we’ve covered the definition and classification of dietary fiber, understood its benefits for the body, and listed high-fiber vegetables, fruits, and other foods. Apart from vegetables and fruits being good sources of dietary fiber, don’t forget that some whole grains, legumes and their processed products, as well as nuts, are also rich in dietary fiber. Gradually increasing fiber intake in a step-by-step manner is key to avoiding unintended consequences.
