Dietary fiber is the main component of plant cell walls, including cellulose, hemicellulose, lignin, cutin and other substances. Before the 1970s, nutritional science only used the term "crude fiber" to describe indigestible food residues, covering only part of cellulose and lignin. It was once widely believed that crude fiber offered no nutritional value to humans, and excessive intake would hinder the absorption of nutrients, especially trace elements, thus exerting adverse effects on the body. For this reason, it drew little attention for a long time.

Later, a series of studies confirmed that these so-called "non-nutritive" indigestible substances are closely tied to human health and play a vital role in preventing coronary heart disease, diabetes, colon cancer, constipation and other illnesses. Meanwhile, the term "crude fiber" was phased out and replaced with "dietary fiber".

The US Food and Drug Administration recommends that healthy people consume a minimum of 11.5 grams of fiber per 1,000 kilocalories of food. Based on an average daily calorie intake of 2,500 kilocalories, adults need at least 25 to 38 grams of fiber each day. Below are the key benefits of high-fiber diets:

Aids weight loss

Cellulose is low in density yet bulky. It fills the stomach and takes longer to digest, delaying gastric emptying and generating lasting satiety to cut total calorie intake. In addition, fiber binds fat in the intestines and eliminates it from the body, reducing fat accumulation.

Stabilizes intestinal flora

Researchers from Stanford University School of Medicine found that insufficient dietary fiber reduces the diversity of gut microbes and disrupts the transmission of intestinal flora between generations. Once offspring gut flora is damaged, supplementary fiber intake cannot reverse the impact.

Relieves and prevents constipation

High-volume dietary fiber absorbs large amounts of water in the digestive tract, enlarging and softening stool, boosting intestinal peristalsis and lowering constipation risk.

Lowers blood lipids

Certain fiber components bind with lipids: pectin combines with cholesterol, while lignin binds with bile acids. Bound cholesterol and bile acids are excreted directly in feces. The body then breaks down stored cholesterol to replenish bile acid reserves, thereby reducing blood lipid levels.

Improves skin condition

When toxic substances build up in the bloodstream, the skin acts as an elimination channel. Facial acne arises from excess acidic substances and saturated fats in the blood. Chronic constipation leads to sallow complexions, as toxins from stagnant stool penetrate the intestinal wall and enter circulation; heavy smoking causes ashen skin for the same reason. Fiber stimulates intestinal movement to speed waste excretion, minimizing toxic damage to the intestinal lining and protecting the skin.

Regulates blood glucose

Insufficient dietary fiber is recognized as one trigger of diabetes. High-fiber foods deliver minimal energy. Pectin in fiber slows intestinal food transit and curbs glucose absorption, preventing sharp post-meal blood sugar spikes and easing diabetic symptoms. It also reduces diabetic patients’ reliance on insulin and oral hypoglycemic drugs.

Absorbs toxins

Digestion naturally produces various toxins that irritate the intestinal mucosal lining. When mixed with water in the digestive tract, cellulose forms a dense mesh structure that traps organic matter, inorganic compounds and water, maintaining balanced gut flora. It adsorbs intestinal toxins, limiting their contact with the intestinal wall and reducing systemic toxin absorption.

Despite these benefits, high-fiber foods should not be consumed to excess at the expense of balanced nutrition. The correct dietary principle is to cut fat intake, raise vegetable and fruit proportions and maintain nutritional diversity. Nutrition specialists advise a daily fiber intake of 25 to 38 grams alongside varied meals. The following methods help meet this target:

1. Eat a diverse range of foods to obtain both soluble and insoluble fiber, both beneficial to health. Replace refined staples with whole-grain options such as whole-grain bread, steamed buns and flatbreads.

2. Breakfast is the ideal time for high-fiber foods. Add fiber-rich nuts, corn and lettuce to other daily meals as well.

3. Legumes are an excellent fiber source and enhance dish flavor; eat legumes 2 to 3 times weekly. Do not skip fruits and vegetables, and consume them with skins when possible. A medium potato with skin contains 3.6 grams of fiber, compared to only 2.3 grams when peeled. Eat seeds of fruits including grapes, kiwis and figs. A daily intake of five servings of fruits and vegetables is recommended.

4. Boost fiber during cooking. Add fiber-rich ingredients: mix oatmeal and whole wheat into congee, red beans and mung beans into rice, and radishes into soups.