Eating foods high in dietary fiber leads to healthy outcomes. Examining the research into fiber fosters an appreciation for the molecular diversity and variations of fiber types, as well as the role fiber plays as a substrate for gut microbial metabolism. Dietary fiber impacts both the function and composition of the microbiota yielding physiologic responses to microbial-derived metabolites of fiber digestion, including protection against obesity and related metabolic diseases.
Although fiber is an essential part of our diet, most Americans fall short of the recommended 25 grams (women) to 38 grams (men) per day (or 14 grams for every 1,000 calories). The Academy of Nutrition and Dietetics recommends that fiber is consumed in adequate amounts as part of a balanced diet.
Dietary fiber provides a sense of fullness after meals and promotes healthy weight. It enhances the diversity of gut microbiota and upregulates microbiome health, increases stool bulk and improves bowel transit time, helps support the maintenance of healthy cholesterol and triglycerides levels, helps maintain blood glucose within a healthy range, helps reduce insulin resistance and decreases gut permeability. Dietary fiber provides similar benefits for children as for adults.
Dietary fiber differs from digestible carbohydrates primarily by the fermentation process. Consumption of dietary fiber requires digestion by microbes, using anaerobic fermentation, the end products of which are short chain fatty acids (SCFA), including butyrate, that exert an anti-inflammatory, immunoregulatory and gut‐brain signalling role.
In addition to the above benefits, the nutrient-dense, “superfood” fiber-sources outlined in this article are known to provide phytonutrients and antioxidants that play important roles in optimizing health:
In addition to the plethora of other well-known benefits, flaxseed is a rich source of fiber. Dietary supplementation of flaxseed will alter the composition of microbiota, specifically increasing the abundance of bifidobacterium.
A rich source of soluble fiber, chia seeds can affect the growth of some healthy bacteria such as lactobacillus, exerting a positive influence on microbial composition. Chia supplementation also has been observed to decrease gut permeability.
Daily intake of broccoli sprouts also had a positive effect on bowel habits of research subjects. In addition, high levels of glucosinolates and sulforaphane provide a strong antioxidant benefit and can decrease overgrowth of some microflora as well as supporting detoxification.
Similar to broccoli, kale is in the cruciferous family of vegetables and contains high levels of glucosinolates. Of the many beneficial actions associated with these sulphur-rich organic compounds, one in particular is that these useful chemical precursors contribute to a prebiotic fermentation process.
Fenugreek seeds contain a high protein and fiber content particularly suited to modifying intestinal bacteria and mitigating dysbiosis. Lab data shows that fenugreek significantly alters intestinal microbial populations.
Sugar Beet Fiber
Beet fiber is a source of pectin and both soluble and insoluble fibers. It increases regularity of bowel movements and promotes growth of the gut microbiota. In addition, fermentation products of sugar-beet fiber by cecal bacteria lowered plasma cholesterol in a study.
Bamboo Shoot Fiber
This novel fiber source has been shown to modulate the composition of gut microbiota. Bamboo shoot fiber also was the most effective type of fiber for mitigating a high fat diet and preventing obesity in mice.
This polyphenol-rich berry delivers significant amounts of intact polyphenols to the colon. One of the effects of these compounds is prebiotic action. In this study there was a reduction in opportunistic bacteria and an increase is SFCAs through digestion and fermentation.
Apples contain bioactive compounds with the potential to alleviate clinical signs associated with obesity, a phenomenon likely related to the composition and function of the gut microbiota. One study showed an increased abundance of Bifidobacterium and a tendency for increased amounts of Lactobacillus, Streptococcus and Enterococcus.
This well-researched fiber can slow gastric emptying, thus providing an increased sense of satiety. A study aimed at determining potential effects of apple-derived pectin on weight gain, gut microbiota and gut barrier suggests that it could also modulate gut microbiota, attenuate metabolic endotoxemia and inflammation, and consequently suppress weight gain and fat accumulation.
While most fiber products contain only extracted fibers, it is important to utilize whole-food fiber sources (such as the ones listed above) that also provide healthy fats and protein, which complement the balance of soluble and insoluble fibers in regenerating the health of the microbiome. In addition, the above fiber types are free of phytates that can impair mineral absorption.
While taking in enough fiber can be challenging for many people, it can be done. It is important to start “low and slow”, ramping up the amount of fiber over time to alleviate the common discomfort experienced when adding too much too fast. When done right, however, benefits can be realized in a fairly short period of time.
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