Any food or nutrients that cannot be processed by the digestive organs of the human body are called dietary fiber or roughage. Fiber absorbs excess water from ingested food and helps the movement of food along the digestive tract, thus helping to maintain healthy bowel function.
Dietary fiber has long been considered a panacea for the gut. There are countless articles extolling its benefits. Fiber is credited with not only preventing and relieving constipation, but also a veritable laundry list of health benefits including aiding weight loss, lowering cholesterol, reducing the risk of diabetes and heart disease, and perhaps even preventing colorectal cancer. Does this mean everyone should blindly increase their intake of fiber?
Types of Fiber:
There are traditionally two major types of fiber – soluble and insoluble. Soluble fiber, as the name suggests, dissolves in water and changes to a gel-like substance which is fermented by gut bacteria. Ideally, if the digestive system is in a healthy state, soluble fiber, in combination with good gut bacteria, performs the function of a probiotic in eliminating disease-causing bacteria that compromise immunity and cause sickness. Soluble fiber is also credited with preventing some types of cancers and reducing blood pressure. Fruits and vegetables are excellent sources of soluble fiber, as are barley, oat bran, and legumes such as peas and beans. Chia seeds are another great source of soluble fiber.
Insoluble fiber remains unchanged as it progresses through the digestive tract, and in effect acts like a sponge to mop up hard-to-reach pockets of the intestines. Whole grains like brown rice, quinoa, millet and bran are good sources of insoluble fiber, as are some vegetables and fruits when eaten with their skins. Insoluble fiber is credited with regulating hunger, controlling blood sugar, and aiding in appetite suppression by creating a feeling of satiation for several hours after a meal rich in insoluble fiber is consumed.
Normal Gut Anatomy:
The large intestine in the human body is home to a population of more than a thousand different types of bacteria. These bacteria perform vital functions such as digesting food, neutralizing toxins, aiding in the absorption of essential nutrients and producing vitamin K which is needed for blood clotting. These “good” bacteria also prevent the overgrowth of harmful infection-causing bacteria.
What is SIBO?
In contrast to the large intestine, the small intestine of a healthy individual has different types and drastically fewer numbers of bacteria. Small intestinal bacterial overgrowth (SIBO) is a disease condition where the number of bacteria increases or unusual types of bacteria are present in the small bowel. Distressing symptoms of SIBO can include:
- Pain and discomfort
- Bloating and distention
- Acid reflux and cramps
- Diarrhea and constipation
- Gas and belching
- Weight loss and malnutrition
The most common treatment for SIBO is antibiotics, but studies have shown that the condition is typically difficult to treat.
Both soluble and insoluble fiber have excellent preventative properties for conditions like constipation and other long-term diseases, but may, in fact, be contraindicated in IBS and SIBO because the fiber can cause overgrowth by feeding the bacteria and worsening the symptoms of these conditions. It may be necessary to clear bacterial overgrowth with antibiotics and ensure the gut is not inflamed before fiber is introduced into the diet people with IBS or SIBO. It is also important to make sure that the ileocecal valve, a sphincter muscle that separates the small and large intestines, is not leaking and allowing backflow of digested food from the large intestine to the small intestine.
What is the link between SIBO and dietary fiber?
Dr. John Hunter, a gastroenterologist at Addenbrooke Hospital in Cambridge in the United Kingdom discovered that a high-fiber diet was worsening the symptoms of his patients with irritable bowel syndrome (IBS). The World Journal of Gastroenterology and studies at Cedars-Sinai Medical Center in the United States have reported a definite association between IBS and SIBO. It is believed that a high-fiber diet can upset the delicate balance in the gut by causing excessive fermentation in the large intestine. Fermenting bacteria not only produce the symptoms commonly associated with IBS, but can also spill over into the small intestine, leading to SIBO.
It seems that soluble and insoluble fibers are both contraindicated in SIBO, so what is the alternative? The answer lies in resistant fiber, a less aggravating fiber that has a delayed digestive reaction. Acted upon by only good bacteria, giving it probiotic functionality, resistant fiber performs its function without leading to aggravation of SIBO. Good sources of resistant fiber are unripe or green bananas, boiled potatoes, cannelloni beans, and some types of peas. Simply put, people who are diagnosed with SIBO must follow a strictly controlled diet such as The Specific Carbohydrate Diet that includes certain specific types of fiber and foods, instead of blindly increasing all types of fiber in their diet.
Dietary Fiber: Is It Good For Everyone?
The recommended daily intake of dietary fiber varies from 20 to 40 grams based on age and gender, but for individuals with SIBO, there are conflicting anecdotal reports of some people being able to tolerate all types of fiber, some people reporting a tolerance to only one sub type of fiber, and some people being unable to tolerate any fiber at all.
Ingestion of fiber prior to exercise has been shown by field and laboratory studies to exacerbate stomachache, vomiting, and reflux or heartburn. Therefore, consumption of fiber is inadvisable before exhaustive exercise. Performing the yoga pose of vajraasna after meals has been found to be helpful in aiding digestion and control distressing symptoms of SIBO.
The link between dietary fiber and SIBO has put a question mark on the age-old belief that eating a wide variety of high-fiber foods, rich in both soluble and insoluble fiber, is good for everyone. It is time to examine if the health benefits of fiber are overestimated, and if fiber may actually be exacerbating gut conditions and causing digestive problems. SIBO can be treated with antibiotics, but it is wise to address the underlying factors which cause it in the first place. Instead of the medical community’s dogged adherence to one train of thought – fiber is good for gut health – it is prudent to explore the value of a low-fiber diet in the prevention of IBS and SIBO and the careful introduction of different types of fiber that are suitable for people with this condition. At the very least, an in-depth investigation into the role of gut bacteria, the recommended daily intake of dietary fiber, and its influence on IBS and SIBO is certainly warranted.