High in fiber, inulin is a collective term for a large group of complex carbohydrates found in nature. Tasteless and odorless, inulin blends easily with fiber compounds and other nutrients. It has been popping up frequently as a component of nutritional supplements that claim to be weight loss aids. Because of its high physiologic utility, inulin is considered a “functional food” and is on the US Food and Drug Administration’s list of Generally Recognized as Safe products.1

Background

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Inulin is composed of large numbers of fructose molecules—up to several thousand strung end to end.2 A soluble dietary fiber, inulin is found in more than 36,000 plant species around the world,3,4 but most inulin is extracted from the chicory root. It has no color and no odor and has little taste.

Inulin exerts substantial prebiotic actions. It has been shown to stimulate growth of the Bifidobacterium species and Lactobacillus species both in vitro and in vivo, likely as a result of the low-level fermentation that occurs in the gut.5,6 Because of this action and its fiber component, inulin is beneficial for the maintenance of gut microflora, for maintenance of blood glucose and lipid homeostasis, and for immunomodulation.5 In addition, inulin has become the gold standard for measuring glomerular filtration rate because of its ability to resist enzyme degradation and reabsorption in the renal tubules.7

Science

Inulin has shown promise in weight reduction as a strategy for those with prediabetes. Researchers randomly assigned 44 subjects to either inulin or plain cellulose supplementation8 and monitored them for weight loss as well as intrahepatocellular and intramyocellular fat and glucose levels. Although both groups lost nearly the same amount of weight by week 9, subjects taking inulin continued to lose weight throughout the following 9 weeks. The percentage of body fat reduced was nearly 3 times greater in the inulin group than in the cellulose group at the end of 18 weeks, and intrahepatocellular lipid levels in the inulin group were reduced nearly 5 times the rate found in the cellulose group.8

In another report, the influence of prebiotics and inulin on bowel movements was studied.9 A group of 38 women who underwent intra-abdominal radiation following surgery for gynecologic cancer was randomly assigned to receive either placebo (maltodextrin) or a prebiotic with inulin and fructo-oligosaccharide.9 Patients reported the number of bowel movements per day, the consistency of the bowel movements, and a self-rating of the quality-of-life indicators of insomnia and diarrhea. At the end of the study, which lasted from before beginning radiation therapy to 3 weeks after the last treatment, patients on the prebiotic formulation reported significantly improved scores regarding the number of days of watery stool, compared with the placebo group. The highest scores for quality of life measures were for insomnia and diarrhea in the placebo group but only for insomnia in the treatment group.

Inulin has also been shown to enhance calcium absorption in the gut, thereby aiding with bone mineralization.10 However, results of short-term studies have been inconsistent. In one, researchers studied the long-term effect of inulin supplementation on bone mineralization in prepubertal teens. One group received inulin-type fructan supplementation and the control group received maltodextrin placebo. At the end of one year, the fructan group showed significantly higher bone mineralization than the placebo group.10

Safety, interactions, side effects

Because inulin itself is not specifically a single entity, its safety is viewed in the context of the plant containing it. Consequently, allergic reactions to plants with high inulin content are possible but rarely reported. There are no documented interactions. Side effects are dose-dependent; the most common side effects are bloating and excessive flatus.

How supplied, dose, cost

The food source with the highest inulin content is chicory root. A serving of 3.5 ounces of this plant contains as much as 48 grams of pure inulin. Chicory root is the main source of commercially prepared inulin in the United States. Inulin is often paired with other supplements such as psyllium fiber for constipation relief. To determine individual tolerance to inulin, starting with a low dose of 2 to 3 grams per day is recommended. The dose can be increased as tolerated over several weeks to a maximum of 20 to 30 grams per day. The cost is variable depending on the form but averages approximately $20 per month’s supply.

Summary

Not often does a natural food substance come along that is adaptable, palatable, and affordable, and has basically no down side. Whether the need is weight loss, diabetes management, intrahepatic fat reduction, or bowel function management, inulin can be a valuable additive to any current regimen.

References

  1. Rulis AM. Agency Response Letter GRAS Notice No. GRN 000118. http://www.fda.gov/Food/IngredientsPackagingLabeling/GRAS/NoticeInventory/ucm153932.htm. Published May 5, 2003.
  2. Inulin. NutrientsReview.com. http://www.nutrientsreview.com/carbs/soluble-fiber-inulin.html. 2016.
  3. Niness KR. Inulin and oligofructose: what are they? J Nutr. 1999;129(7 Suppl): 1402S-1406S.
  4. Mensink MA, Frijlink HW, van der Voort Maarschalk K, Hinrichs WL. Inulin, a flexible oligosaccharide. II: Review of its pharmaceutical applications. Carbohydr Polym. 2015;134:418-428.
  5. Boeckner LS, Schnepf MI, Tungland BC. Inulin: a review of nutritional and health implications. Adv Food Nutr Res. 2001;43:1-63.
  6. Schaafsma G, Slavin JL. Significance of inulin fructans in the human diet. Comprehensive Reviews in Food Science and Food Safety. 2015;14(1):37-47.
  7. Franck A. Technological functionality of inulin and oligofructose. Br J Nutr. 2002;87(Suppl 2):S287-S291.
  8. Guess ND, Dornhorst A, Oliver N, Bell JD, Thomas EL, Frost GS. A randomized controlled trial: the effect of inulin on weight management and ectopic fat in subjects with prediabetes. Nutr Metab (London). 2015;12:36.
  9. Garcia-Peris P, Velasco C, Hernandez M, et al. Effect of inulin and fructo-oligosaccharide on the prevention of acute radiation enteritis in patients with gynecological cancer and impact on quality of life: a randomized, double-blind, placebo-controlled trial. Eur J Clin Nutr. 2016;70(2):170-174.
  10. Abrams SA, Griffin IJ, Hawthorne KM, et al. A combination of prebiotic short- and long-chain inulin-type fructans enhances calcium absorption and bone mineralization in young adolescents. Am J Clin Nutr. 2005;82(2):471-476.

All electronic documents accessed August 15, 2016.

From the September 01, 2016 Issue of Clinical Advisor

Topics:

Complementary and Alternative Medicine Diet and Nutrition Nutrition