Both conventional and functional medicine can agree that most people in our nation need more fiber. The average American diet includes more and more processed ingredients with less and less old-fashioned fiber, leaving many missing out on fiber’s benefits. We can all agree that most patients can see benefits like lower cholesterol, better gut health with less constipation, improved metabolic health, and lower cancer rates. Despite this consensus, in caring for patients with a wide variety of conditions and needs, we can sense that different people respond differently to different fiber types. In other words, not all fibers are equal in their benefits or effects. With these suspicions, researchers studied the effects of two different fiber types and reported their findings in Cell Host & Microbe.
Prior research demonstrates the effects of high-fiber diets in various diseases. Fiber intake reduces the risk of cardiovascular disease. (1,2,3) It helps heal leaky gut through their contribution to the production of short chain fatty acids. For many, fiber addresses the issue of constipation through increasing stool bulk and moisture content. Fiber intake keeps gut bacterial balance in check by feeding good bacteria. Fiber helps the production of B vitamins and vitamin K. It can even help pull out some toxins like mycotoxins during detox protocols.
Beyond just advising patients to eat more fiber, researchers want to know which fibers may be more beneficial in different situations. Clearly not all fibers are the same. Some contribute more to short chain fatty acid production. Some appear to have a greater cholesterol lowering effect. Some have more benefit for constipation and others less. With that in mind the researchers in this study compared two fiber types, arabinoxylan (AX) from whole grains and long-chain inulin (LCI) found in Jerusalem artichokes, onions, and chicory root.
Several reasons for the differences lie within the various molecular structures of fiber types. Fiber molecules vary in what sugars are included, in their length, how much they branch, the patterns of their branching as well as the resulting solubility in water, their electrical charges and other properties. In foods, these various characteristics come mixed and make an understanding of specific effects of specific fibers more difficult. To overcome this difficulty, researchers used the purified forms of the AX and LCI instead of regular food sources.
AX has been reported in prior research to help with high blood pressure, lowering bad cholesterol (LDL), and lowering blood sugar. (4,5,6,7). LCI is known to increase the good bacteria Bifidobacterium (8,9,10) (Hidaka, Kokida, Slavin), lower constipation (11,12), improving glucose control and A1c in diabetes (13), and helping bone health (14). In the case of inulin, there also seems to be a dose dependent effect with higher doses appearing to harm the liver (15,16).
This study compared AX, LCI, and a combination fiber which included other fibers common in food products. Between groups they compared “stool metagenomics, plasma proteomics, metabolomics, lipidomics, serum cytokines, and clinical values.” The average age of participants was 56.9 years and most began with mostly healthy clinical markers except for borderline high cholesterol levels.
In the study, there were a few general conclusions. First, there were some changes in objective and subjective findings which were common to both fiber types. Second, while there were some differences between fiber types, there was also a pattern of individuals responding to fiber differently from other test subjects. Third, despite titrating up slowly from 10 to 20 to 30 grams over 1-week intervals, a number of individuals reported some side effects like bloating and flatulence. Beyond that the original article describes a number of other differences between AX and LCI which included differences in bacterial balance and reported clinical changes. At the highest level of LCI intake, there were some microbiome changes which might lead to adverse effects as well as a mild increase in the liver enzyme alanine aminotransferase (ALT). This liver test abnormality resolved when the LCI was stopped.
Without going into the detail of the article itself, one can take away the following: Soluble fibers like AX and LCI have benefits for our health in moderate doses that come in foods or supplementation; LCI can be harmful at higher doses; medical research needs to further evaluate the variable effects of different fibers on different health conditions as well as factors that influence how a particular person will respond to a given fiber. Helping others live healthier more abundant lives requires both research and practical applications.
Samuel M. Lancaster, Brittany Lee-McMullen, Charles Wilbur Abbott, Jeniffer V. Quijada, Daniel Hornburg, Heyjun Park, Dalia Perelman, Dylan J. Peterson, Michael Tang, Aaron Robinson, Sara Ahadi, Kévin Contrepois, Chia-Jui Hung, Melanie Ashland, Tracey McLaughlin, Anna Boonyanit, Aaron Horning, Justin L. Sonnenburg, Michael P. Snyder. Global, distinctive, and personal changes in molecular and microbial profiles by specific fibers in humans. Cell Host & Microbe, 2022; DOI: 10.1016/j.chom.2022.03.036 . Accessed 5/11/22.
Thanks to Science Daily:
Cell Press. “Not all dietary fibers are equal.” ScienceDaily. ScienceDaily, 28 April 2022. <www.sciencedaily.com/releases/2022/04/220428125440.htm>. Accessed 5/11/22.
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Sanctuary Functional Medicine, under the direction of Dr Eric Potter, IFMCP MD, provides functional medicine services to Nashville, Middle Tennessee and beyond. We frequently treat patients from Kentucky, Alabama, Mississippi, Georgia, Ohio, Indiana, and more... offering the hope of healthier more abundant lives to those with chronic illness.