Functional Foods & Nutrients

High Fiber Diet

You have been told to eat a high-fiber diet or have learned somewhere that a high-fiber diet is good for you.  But what exactly is fiber?  The scientific definition first.  Fiber is carbohydrate polymers with 10 or more monomeric units that are not hydrolyzed (broken down) by endogenous (made by our body) enzymes in the small intestine.  Fiber is more complex than simply saying eat your fruits and vegetables.  Dietary fiber (the fiber that is found in food) is more than a single ingredient, it exists in a wide variety of foods and has variable physicochemical (molecular) properties and physiological (functional) impacts that contribute to health promotion and disease prevention.  

The American Heart Association recommends consuming 25-30 grams of dietary fiber a day to reduce the risk of disease and the America College of Gastroenterology recommends doubling your fiber intake to 20-35 grams a day to improve multiple GI complaints.  Rather than broadly recommending a “high” fiber diet, it would seem wiser to promote eating a “higher” fiber diet as most Americans consume less than 15 grams a day.   Eating a diet that contains a variety of fibers from foods has been shown to reduce the risk of multiple non-communicable diseases (NCDs), which contributes to 74% of all deaths globally. 

Choosing to eat more fiber daily has a significant impact on our gut health, influencing the function and composition of our microbiota. These are the meaningful microbes found in our colon (large intestine) and when dietary fibers are delivered our microbes are capable of a fermentation process that produce metabolites known as short-chain fatty acids (SCFA).  These SCFAs not only provide localized health benefits but when absorbed they extend throughout the body providing a robust immune function in addition to many other physiological health benefits.

1. McKeown NM, Fahey GC, Slavin J, van der Kamp JW. Fibre intake for optimal health: how can healthcare professionals support people to reach dietary recommendations? The BMJ. 2022;378:e054370. doi:10.1136/bmj-2020-054370