At a glance
- Different dietary fiber supplements were associated with various health benefits, such as lowering cholesterol and increasing the number of beneficial bacteria.
- The findings suggest that the health benefits of dietary fiber depend on the type, amount, and individuality of fiber.
Fiber is an essential part of a healthy diet. High-fiber diets have been linked to health benefits, such as improved metabolism and heart health. However, 5% of the U.S. population consumes recommended fiber levels. Supplemental fiber can help fill that gap, but the health effects of purified supplemental fiber have not been well studied.
There are two types of dietary fiber. Soluble fiber mixes with water and slows digestion. They are linked to a reduction in the risk of heart disease, lower cholesterol levels and better control of blood sugar. Soluble fiber can be found in some grains, seeds, legumes, and various vegetables. Insoluble fiber is found in foods such as whole grains, beans and roots. They act as a bulk that can help food and waste pass through the intestines more easily. The health effects of different dietary fibers, especially the most soluble ones, depend in part on their interactions with the microbes that live in the gut, the gut microbiome.
A team funded by the NIH at Stanford Medical School, led by Dr. Michael Snyder, studied the effects of consuming different types of fiber. They enrolled 18 participants — ten women and eight men — and provided them with additional fiber for three weeks. The supplements included a mixture of arabinoxylan (AX), long-chain inulin (LCI) and five fibers. AX and LCI are well-known supplements for purified soluble fibers. AX is found in whole grains and other plants, and LCI chicory is found in roots such as roots and onions and artichokes.
Each participant took each supplement for three weeks, with intervals of 6 to 8 weeks, without taking any fiber supplements. The researchers made several measurements during the study from blood and stool samples. They examined a number of health markers, including those involved in metabolism and immune function. Participants also kept food records so that researchers could monitor their entire diet, including fiber from other sources. The results were released on April 27, 2022 Host cell and microbe.
The group found that different types of fiber have different effects on human health markers. For example, for most people, AX was associated with lowering cholesterol and bile acids, which are made from cholesterol. It was associated with increased LCI Bifidobacterium, a beneficial intestinal bacterium. Both forms of purified dietary fiber had stronger effects than fiber blends.
Although most of the changes observed were beneficial, high doses of LCI increased inflammation and were associated with high levels of alanine aminotransferase for a few people, which may be a sign of liver damage. In addition, the diversity of intestinal microbes decreased as people were taking in purified fiber supplements.
The effects of fiber supplements were special to different people. Some people, for example, did not lower their cholesterol by ingesting the AX supplement, but did consume LCI. The results suggest that, although some general trends may be common, the optimal fiber intake for each person may vary. More work is needed to study the findings that affect these findings and the different fibers that affect health.
“Overall, our findings show that the benefits of fiber depend on the type of fiber, dose, and participant, landscape of factors that interact with fiber, intestinal microbiome, and host,” says Snyder. “These results have important implications for personalized responses and interventions.”
—Larisa Gearhart-Serna, Ph.D., MBA
References: Global, distinctive, and personal changes in molecular profiles and microbes of specific human fibers. Lancaster SM, Lee-McMullen B, Abbott CW, Jaw JV, Hornburg D, Park H, Perelman D, Peterson DJ, Tang M, Robinson A, Ahadi S, Contrepois K, Hung CJ, Ashland M, McLaughlin T, Boonyanit A, Horning A, Sonnenburg JL, Snyder MP. Host Cell Microbes. April 22, 2022: S1931-3128 (22) 00166-4. doi: 10.1016 / j.chom.2022.03.036. Before printing online. PMID: 35483363.
Funding: NIH National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Center for Complementary and Integrative Health (NCCIH) and Office of the Director (OD).