Adequate intake of dietary fiber (with sufficient amounts of soluble fiber) can help ensure stable gut barrier function and benefit blood sugar control, cholesterol levels, digestive health, and systemic inflammation; contributing to more balanced sebum production and composition, and reduced skin sensitivity.
Section has been renamed
This section used to be called “Soluble Fiber” as my research had suggested that this type of fiber is the optimal fuel for the friendly bacteria of our digestive system. Further research highlighted the complexity of the subject and this section has been updated accordingly to include discussion of overall “dietary fiber” intake.
Dietary fiber is essentially the part of plant foods that the body can’t directly digest or absorb. However, the bacteria living inside of our digestive tract (gut microbiota) are quite capable of fermenting the fiber and produced valuable by-products (short-chain fatty acids, gases, and other metabolites )
High fiber diets are a trending topic in health and chronic disease prevention for a good reason. Recent investigation shows that without adequate amounts of dietary fiber, a shift in the microbiota composition can degrade the mucosal barrier causing bacterial translocation . The end result is increased levels of inflammation, unstable immune function, and abnormal nutrient absorption.
Different Types of Fiber
At this point, most individuals eating whole grains typically assume that they are likely getting enough fiber as is. However, not all fiber is created equal and unfortunately, this important fact is not always considered.
Fiber can be divided into two main categories:
- Soluble fiber – thickens water (forming a jelly-like substance) and most commonly found in fruits, vegetables, legumes and certain cereal (such as oats)
- Insoluble fiber – fibrous material and most abundant in wholegrain cereals
Though both types of dietary fiber are known to produce beneficial effects on blood sugar control, soluble fiber is considered to be the primary food source of the beneficial bacteria of the large intestine . Accordingly, soluble fiber has shown a wider variety of potential health benefits (particularly related to digestive health and immune function).
Now, where does this fall into a historical perspective? Well, just consider the following statistic:
- “Daily fiber intakes in ancient diets could reach 100 g, mostly in the form of soluble fiber, whereas adults in industrialized countries typically eat only 15 g of fiber, falling short of the recommended daily intake of 20-30 g and mostly in the form of insoluble fiber.” 
Well, diets change and life expectancy has increased, right? How bad can low soluble fiber intake really be? Well, perhaps the following illustration can provide some perspective:
As you can see, no matter what dietary approach you take, adequate dietary fiber intake is critical.
More specifically, a diet high in soluble fiber has been shown to promote the growth of beneficial bacteria and stimulate short chain fatty acid (SCFA) production. This in-turn has far-reaching effects on immune system stability and helps ensure adequate gut barrier integrity .
Documented Benefits of Soluble Fiber and SCFA
Soluble fiber is best known for it’s ability to:
- Reduce blood cholesterol (LDL) levels [7, 8, 9, 10]
- Regulate blood glucose levels (preventing sugar spikes) [11, 12]
- Improve gut health and act as a food source for bacteria in the large intestine 
- Modulate immune system function [14, 15]
- Reduced levels of systemic inflammation (due to short chain fatty acid production) 
Since most of the benefits of fiber appear to be derived from the short chain fatty acids produced via fermentation by the microbiota it makes sense to review the specific role that SCFAs play.
Some documented functions of short chain fatty acids include:
- Regulate many metabolic functions (glucose, fatty acids, cholesterol) 
- Play a role in body weight and insulin sensitivity 
- Regulate immune cell function [19, 20, 21]
- Control inflamattion and act as anti-infalmattory mediators [22, 23, 24]
Taken together, it becomes evident that many chronic inflammatory conditions may be partially driven by insufficient dietary fiber intake and resulting alterations of the microbiota composition.
Focusing Solely on Soluble Fiber Is Likely Insufficient
Based on the benefits of soluble fiber, one would presume that strictly increasing its consumption via supplementation or strict selection of foods would be beneficial. Unfortunately, it’s not that easy.
Studies investigating the health-promoting effects of soluble fiber have shown that:
- Soluble fiber is drastically more efficient in combination with insoluble fiber and other components of whole food 
- Eating foods containing prebiotics does not have the same beneficial effect as actually consuming dietary fiber 
- Only foods sources are known to have “complete” sources of dietary fiber 
It appears that soluble fiber and its utilization by the microbiota throughout the digestive is favorably affected by insoluble fiber. The insoluble fiber ensures that soluble fiber is gradually degraded throughout its journey, as opposed to rapid utilization in the initial stages of passage.
Accordingly, focusing on foods that are naturally high in both soluble fiber and insoluble fiber makes the most sense.
Why Dietary Fiber is Important for Inflammatory Skin Disease
Characteristics of adequate dietary fiber intake which are most important for individuals affected by inflammatory skin disorders include:
- Improved blood sugar control
- Improved immune system function
- Reduced systemic and inflammation
- Balanced sebum production
- Reduced skin hypersensitivity
Ideas for Increasing Soluble Fiber Intake
Based on the nutrient mix, soluble fiber content, overall fiber content and typical portion size, the best sources of soluble fiber are:
- Vegetables – brussels sprouts, carrots, celery, asparagus, onions
- Fruits – apples, oranges, apricots
- Root tubers – potatoes, artichoke, sweet potato, yam, cassava
- Legumes – peas, lentils, beans
- Barley and oat bran
Aiming for a good mix helps ensure you also obtain a good variety of nutrients.
By meeting the various other dietary objectives introduced in this program (such as consumption Vitamin A rich plant foods, low GI foods, cruciferous vegetables, and apples), you likely don’t need to make too many adjustments to meet your soluble fiber objective.
- If your coming from a diet low in soluble fiber, you may experience some cramping and bloating when you first introduce ample amounts of soluble fiber. If this is the case, start slow and gradually increase the amount of soluble fiber in your diet
- There are actually different sub-types of soluble fiber (such as beta-glucans), with some having more significant beneficial impacts on health then others, but this discussion may produce unnecessary complexity
- Insoluble fiber is best known for its laxative properties and improving bowel movement regularity
- Diets high in soluble fiber typically also have a low glycemic index
- Soluble fiber stimulates the production of short chain fatty acids within the gut and this is known to have a significant beneficial impact on immune function
- Insoluble fiber (in the absence of soluble fiber) supplements may be of little use and could actually produce negative outcomes [28, 29]
Mucosal integrity and adequate SCFA production may be the key to various chronic health conditions
Accumulating evidence suggests that the microbiota is an integral component of the human body. A complex and mutually beneficial relationship with the bacteria which reside in our gut ensures obtain vital nutrients otherwise unavailable. By depriving our gut microbiota, we may be sacrificing our health in unprecedented ways.