Increased consumption of dietary fiber to at least the recommended daily levels has been shown to improve several symptoms as well as reducing the relative and absolute risk of developing several diseases.
Women need approximately 25 grams of fiber per day, and men need approximately 38 grams per day (source).
Let’s look at health benefits of consuming enough fiber daily.
Constipation and Stool Texture
In general, dietary fiber has a bulking effect on your stool, making it easier to defecate and thus reducing symptoms of constipation, diarrhea and watery stools.
When digested foods pass through the intestines too fast, there isn’t enough time for water to be completely absorbed, resulting in watery stools and diarrhea.
On the other hand, if the passage of waste is too slow, too much water is absorbed, resulting in hard stools and constipation, which often leads to straining. These simple problems occasionally lead to inflammation of the digestive tissues, that has been correlated with the development of cancer and other diseases.
Dietary fiber helps regulate the transit time by promoting peristalsis, the wavelike contractions that keep food moving through the intestine. Also, high-fiber foods expand the inside walls of the colon, helping ease the passage of waste. Insoluble fiber passes through the intestine undigested and absorbs many times its weight in water, resulting in softer, bulkier stools.
The reduced transit time prevents the stagnation of food in the small pouches of your colon (reducing the risk for diverticulitis) as well as making it easier to defecate.
Beneficial effect on the digestive tract
Consumption of both soluble and insoluble fiber has been shown in several studies to be beneficial for a number of digestive tract disorders, in particular neoplastic episodes (cancer), inflammatory diseases and auto-immune disorders.
The bulk of your stool promotes the cellular turnover, making sure that the cells lining your digestive tract are always young and functional (since old cells are exfoliated): this is beneficial in conditions such as hemorrhoids, irritable bowel syndrome and diverticular disease.
Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is one of the most common disorders of the lower digestive tract. It is associated with bothersome symptoms such as constipation, diarrhea, bloating, abdominal pain, cramping, and spasms and if left untreated, it may lead to diverticulosis of the colon.
IBS attacks are usually triggered by emotional tension, poor dietary habits, and certain medications. Increased amounts of fiber in the diet can help relieve the symptoms of irritable bowel syndrome by normalizing the time it takes for the stool to pass through the colon.
Fiber and Colon Cancer / Polyposis
Colon cancer is a life-threatening condition most common in Western countries. Most malignant colon cancers (carcinoma) start out as a benign mushroom-shaped formation, called polyp. With the passage of time it tends to grow, and may become malignant: it is usually always curable, but only if polyps are removed early, before they have had a chance to become malignant and spread cancerous cells to other parts of the body (metastasis).
In zones with a high consumption of dietary fiber, the rates of colon cancers are extremely lower (down to 1/20th). The theory is that in the Western world, carcinogens and toxic substances remain in contact with the colon wall for a longer time and in higher concentrations, and the absence of fiber causes the cells forming the lining of the digestive tract to not be turned over as fast, giving them a chance to undergo genetic mutations and becoming cancerous.
Cardiovascular and Systemic benefits
Soluble fiber has been shown to greatly reduce some of the major risk factors for coronary and cardiovascular disease, in particular blood concentration of triglycerides and cholesterol.
Soluble fiber has a regulatory effect on the amount of fats that are released in the bloodstream by your adipose cells, down-regulating the quantity of LDL (low density lipoproteins), which are responsible for the transport of fats and are also known as “bad cholesterol”.
Some sources also claim that fiber reduces the absorption of cholesterol on a mechanical basis, but this has yet to be proven true. Foods suitable for reducing hyperlipidemia are flax seeds, bran, beans, peas and oats.
Diabetes and blood sugar levels
Fats in your bloodstream compete with glucose (blood sugar) to bind to insulin: people with high levels of triglycerides are at higher risk of developing insulin resistance, that eventually leads to type 2 diabetes.
Soluble fiber, by reducing the amount of blood fats, directly affects blood sugar levels and reduces insulin resistance, leading to a markedly lower risk of developing type 2 diabetes. Consumption of soluble fiber is also recommended as an auxiliary treatment for those patients that have already developed type 2 diabetes, since it’s been shown to ameliorate the symptoms and lead to a better prognosis.
Weight Loss and obesity
Dietary fiber has a very low caloric density, meaning you can eat a lot and feel full without ingesting a lot of calories. Soluble fiber also has a regulatory effect on your appetite by regulating satiety hormones, while insoluble fiber takes longer to digest and prevents you from feeling hungry too early.
The increased chewing time is also beneficial in giving your body the time to detect that you’re no longer hungry (it normally takes at least 10 minutes), so you don’t overeat. Overall, the combined effects have been shown to aid in substantial weight loss regimens.
Digestive Tract Cancers
Studies have shown that eating the recommended daily values of dietary fiber reduces the risk of developing several digestive tract cancers, in particular squamous carcinoma and adenocarcinoma (that typically affect the esophagus).
Insoluble fiber promotes a thicker lining in your digestive tract, making it more resistant to carcinogenic infections such as Helicobater pylori and reducing the risk of peptic ulcers (which have been shown to be strongly linked with gastric and duodenal cancer).
The thicker texture of your stool promotes a higher cellular turnover in your colon, making sure that no old cells have the time to undergo mutations and develop into a colorectal cancer: insoluble fiber has been shown, in fact, to reduce the risk of colorectal cancer by substantial percentages.