It is estimated that 95% of American adults and children do not consume the recommended amounts of fiber. Because of the significant gap between total fiber intake and fiber recommendations, the Dietary Guidelines for Americans have identified fiber as a "nutrient of concern" since 2005. The continuing low levels of fiber intake are considered a public health concern in light of the health benefits related to adequate fiber intake
Higher dietary fiber intake has been associated with a reduced risk of developing chronic diseases such as type 2 diabetes, cardiovascular disease, and some cancers. Adequate fiber intake has also been associated with lower body weight.
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What is Fiber?
Fiber is a type of carbohydrate that the body can't absorb or digest. Though most carbohydrates and proteins are broken down into small molecules, humans cannot break fiber down; therefore, it is not digested and thus passes relatively intact through the digestive system. This benefits humans, as the undigested fiber feeds our healthy bacteria as it passes through our large intestine.
Fiber can be viscous with a gel-like quality and also fermentable because it acts as food for gut microbiome bacteria that break down the fiber and ferment it. Fibers not broken down by bacteria are nonfermentable and travel intact to the colon. This offers health benefits such as delaying blood glucose rises after meals, slowing down digestion, promoting the growth of healthy colonies of bacteria, or having a laxative effect.
There are several subtypes of soluble and insoluble fibers, some of which occur naturally in plant foods while others are synthetically made.
The National Academy of Medicine defines fiber as:
- Dietary fibers: that occur naturally in plants. These are cellulose, hemicellulose, lignins, beta-glucans, guar gum, Inulin, oligofructose, oligosaccharides, fructooligosaccharides, pectins, and resistant starch.
- Functional fibers: are isolated or extracted forms of dietary fibers such as psyllium, chitin and chitosan, Fructooligosaccharides, Galactooligosaccharides, Polydextrose and polyols, and resistant dextrins.
How Many Grams of Fiber Should We Be Consuming Per Day?
The adequate intake for dietary fiber is 14 g total fiber per 1,000 kcal based on research evidencing protection against heart disease.
However, the mean dietary fiber intake in the US is 17 g/day, and worryingly only 5% of the population reaches the Adequate intake.
Adults and children can achieve healthy dietary fiber intake by increasing their consumption of plant foods. Here is an estimative idea of fiber requirements for age groups:
- Children 1-3 years: 19 grams of fiber/day.
- Children 4-8 years: 25 grams of fiber/day.
- Boys 9-13 years: 31 grams of fiber/day.
- Girls 9-13 years: 26 grams of fiber/day.
- Boys 14-19 years: 38 grams of fiber/day.
- Girls 14-19 years: 26 grams of fiber/day.
What are The Differences Between Soluble Fiber and Insoluble Fiber?
Soluble Fiber is a type of fiber that dissolves in water, forming a gel-like material. This fiber can help lower blood glucose and cholesterol levels. ·
Insoluble fiber doesn't dissolve in water which promotes the passage of fecal material through the digestive system increasing stool bulk. Insoluble fiber is beneficial in cases of constipation or irregular stools.
What are The Health Benefits of Fiber?
Both Soluble and Insoluble fiber have varying health benefits. Some common health benefits they both share are:
- A diet high in soluble and insoluble fiber increases the stool's weight and size and softens it. This decreases the chances of constipation as it makes stool easier to pass through the intestines.
- As some fiber is fermented in the colon, Scientific research is ongoing to understand how fiber fermentation plays a role in preventing bowel diseases.
- Some studies have found that a high-fiber diet likely lowers the risk of colorectal cancer.
- Foods containing high fiber may have other heart-health benefits, such as reducing inflammation and blood pressure.
- It helps achieve a healthy weight. A high soluble and insoluble fiber diet is more filling than a low-fiber diet. Because high-fiber foods tend to be less dense in energy and take longer to eat, it results in fewer calories for the same volume of food.
- Increases longevity. Some studies suggested that increasing dietary fiber reduces the risk of dying from cardiovascular disease and cancer.
What are The Health Benefits of Soluble Fiber?
A high-soluble fiber diet has several health benefits, such as:
- It helps to normalize bowel movements.
- When soluble fiber turns to gel after digestion, it slows the process down in the digestive tract, helping bulk up stools, and benefits those suffering from diarrhea.
- Lower the risk of developing colon and intestine alterations such as hemorrhoids and diverticular disease.
- A high-soluble fiber diet may help to decrease total cholesterol levels in the blood by lowering low-density lipoprotein.
- A high-soluble fiber diet can slow the absorption of sugar and improve blood glucose levels.
- Soluble fiber reduces your body's ability to absorb fat.
What Foods are High in Soluble Fiber?
Eating a wide variety of high-fiber foods is advisable as the amount of insoluble and soluble fiber varies in different plant foods. All fruits, vegetables, whole grains, and legumes contain some soluble fiber, but certain foods like flax seeds, brussels sprouts, avocados, and black beans have a much higher content. Below is a list of 20 healthy foods that are high in soluble fiber:
- Black beans
- Lima beans
- Brussel sprouts
- Avocados
- Sweet potatoes
- Broccoli
- Turnips
- Pears
- Kidney beans
- Figs
- Nectarines
- Apricots
- Carrots
- Apples
- Guavas
- Flax seeds
- Sunflower seeds
- Hazelnuts
- Oats
- Barley
To increase the soluble fiber intake, it's often recommended to start slowly and build it up gradually. It's also good to drink plenty of water while eating high-fiber foods. This will help the soluble fiber form a gel, which prevents constipation and aids digestion.
What are The Health Benefits of Insoluble Fiber?
Insoluble fiber can help promote both bowel health and regularity. The insoluble fiber attracts water into the stool, making it softer and easier to pass through the digestive system with less strain on the bowel, making it a perfect addition for those who suffer from constipation. Insoluble fiber also supports insulin sensitivity and, like soluble fiber, may help reduce the risk of diabetes.
What Foods are High in Insoluble Fiber?
Below are some of the top insoluble fiber foods:
- Oat bran
- Wheat bran and wheat germ
- Beans, lentils, and legumes of all kinds: kidney, garbanzo, black, edamame, split peas, lima, navy, white, etc.
- Berries, including blackberries, raspberries, blueberries, strawberries, etc.
- Whole grains, especially quinoa, barley, sorghum, amaranth, millet, oatmeal, and rye
- Turnips
- Green peas
- Rutabaga
- Coconut (grated flakes or flour)
- Cocoa
- Okra
- Spinach
- Radishes
- Apples with skin
- Pears with skin
- Flaxseeds
- Avocado
- Sunflower seeds
- Potatoes and sweet potatoes
- Dried apricots, prunes, raisins, dates, and figs
- Almonds
- Walnuts
- 100% whole grain pasta and bread
- Passionfruit
- Popcorn
Tips for Getting More Fiber?
To increase your fiber intake, eating whole fruits instead of drinking fruit juices is suggested. Replace white rice and pasta with brown rice or whole grains like barley, amaranth, millet, and farro. Add high-fiber foods like ground flaxseeds or chia seeds to cereals or main dishes. Add diced vegetables to casseroles, soups, and stir-fried dishes. You can choose cereals with whole grains as their main ingredient for breakfast.
Consider changing your snacks to crunchy raw vegetables or a handful of almonds instead of chips and crackers—substitute legumes of beans for meat at least two to three times a week.
If you find it challenging to eat enough fiber through food, consider a fiber supplement such as methylcellulose powders or psyllium. Please note that fiber supplements are not intended to replace high-fiber foods completely.
Summary
There are many types of dietary fibers, soluble and insoluble, that come from a range of plant foods. It is recommended not to hyperfocus on a particular fiber because of its specific proposed action, as all fibers offer many health benefits. Thus, eating a wide variety of plant foods like fruits, vegetables, legumes, nuts, whole grains, and seeds to reach the fiber intake recommendation of 25-35 grams daily.
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