Understanding Soluble Fiber: Inulin

Understanding Soluble Fiber: Inulin

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Fiber 101

Most of us now understand that fiber should be an essential part of our everyday diet. However, most people don’t know that there are two types of fiber: Soluble and Insoluble. They are both critical for health. What’s the difference? Simply put, soluble fiber absorbs water, and insoluble fiber doesn’t. Soluble fiber comes from many sources, including oats, nuts, beans, fruits, and veggies. Insoluble fiber is found in seeds, bran, and whole grains and mainly adds bulk to your stool. A dentist friend used to call insoluble fiber “the toothbrush of the colon.”

One of the most popular dietary supplement forms of soluble fiber is Inulin. Inulin is a “starchy” (good starch because it can’t be digested and add calories) substance found in chicory roots, leeks, onions, artichokes, and other plant foods. In the scientific field, Inulin is a short-chain oligosaccharide, often referred to as fructooligosaccharides (FOS). To keep this simple, fructooligosaccharides are a combination (chain) of simple sugars and will have zero caloric impact. It is commonly found in probiotic supplement products because it is used as a “fertilizer” for good bacteria.

What are the health benefits of Inulin?

Digestive Health (Amount needed: 2-10grams daily)

Inulin absorbs the water in your digestive system and helps provide bulk to your stool. In addition, research shows that Inulin helps with constipation by improving stool frequency, stool transit time, consistency, and hardness.[i]  Because it absorbs water from the gut, it can also help firm up the stools in bouts of diarrhea. Additionally, Inulin has a prebiotic effect, meaning that it is not digested or absorbed but instead promotes the growth of specific types of bacteria in the large intestine. Inulin has been suggested to stimulate the growth of Bifidobacterium and Lactobacillus preferentially,[ii] [iii] [iv] [v] two prevalent probiotic strains.

Blood Sugar (Amount needed: 0.8-10grams daily)

Replacing digestible carbohydrates in foods with Inulin leads to lower blood sugar levels after meals.[vi]  Having more non-digestible carbs (soluble fiber) and fewer digestible carbs means you will be consuming less food that can easily be converted into sugar. For example, a study done with people who had type 2 diabetes showed that taking Inulin (0.8-10 grams daily) for 6-12 weeks reduces hemoglobin A1C and fasting glucose compared to people who did not consume Inulin.[vii] [viii]

Weight Management (10-18grams daily)

Inulin’s effects on body weight are thought to be due to reduced ghrelin levels. Ghrelin is a hormone produced in the gut that gives a feeling of satiety and reduces hunger.[ix] [x]

Cardiovascular health (1.5-10grams daily)

Inulin decreases triglycerides by decreasing fatty acid production and reduces the production of very low-density lipoproteins (LDL-cholesterol). [xi] [xii] In short, Inulin positively impacts the lowering of cholesterol and triglycerides when consumed in the proper amounts daily.

While fiber may not be a sexy topic, it is vital that we consume 25 grams or more weekly. Ideally, you should consume more whole foods already high in soluble and insoluble fiber. Being realistic, though, for many people, this is a challenge both due to living in a “food desert” or due to the expense of eating whole foods. Therefore, looking for dietary supplements and functional foods and beverages should be part of your shopping experience.

[i] Collado Yurrita L, San Mauro Martín I, Ciudad-Cabañas MJ, Calle-Purón ME, Hernández Cabria M. Effectiveness of inulin intake on indicators of chronic constipation; a meta-analysis of controlled randomized clinical trials. Nutr Hosp 2014;30(2):244-52

[ii] Closa-Monasterolo R, Ferré N, Castillejo-DeVillasante G, et al. The use of inulin-type fructans improves stool consistency in constipated children. A randomised clinical trial: pilot study. Int J Food Sci Nutr. 2017;68(5):587-594.

[iii] Nicolucci AC, Hume MP, Martínez I, Mayengbam S, Walter J, Reimer RA. Prebiotics reduce body fat and alter intestinal microbiota in children who are overweight or with obesity. Gastroenterology. 2017;153(3):711-722

[iv] Marteau P, Jacobs H, Cazaubiel M, Signoret C, Prevel JM, Housez B. Effects of chicory inulin in constipated elderly people: a double-blind controlled trial. Int J Food Sci Nutr 2011;62(2):164-70

[v] Gibson GR, Beatty ER, Wang X, Cummings JH. Selective stimulation of bifidobacteria in the human colon by oligofructose and Inulin. Gastroenterology 1995;108:975-82.

[vi] Lightowler H, Thondre S, Holz A, Theis S. Replacement of glycaemic carbohydrates by inulin-type fructans from chicory (oligofructose, inulin) reduces the postprandial blood glucose and insulin response to foods: report of two double-blind, randomized, controlled trials. Eur J Nutr 2018;57(3):1259-68

[vii] Rao M, Gao C, Xu L, et al. Effect of inulin-type carbohydrates on insulin resistance in patients with type 2 diabetes and obesity: a systematic review and meta-analysis. J Diabetes Res. 2019;2019:5101423

[viii] Zhang W, Tang Y, Huang J, Yang Y, Yang Q, Hu H. Efficacy of inulin supplementation in improving insulin control, HbA1c and HOMA-IR in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials. J Clin Biochem Nutr 2020;66(3):176-83. doi: 10.3164/jcbn.19-103

[ix] Harrold JA, Hughes GM, O’Shiel K, et al. Acute effects of a herb extract formulation and inulin fibre on appetite, energy intake and food choice. Appetite 2013;62:84-90.

[x] Heap S, Ingram J, Law M, Tucker AJ, Wright AJ. Eight-day consumption of Inulin added to a yogurt breakfast lowers postprandial appetite ratings but not energy intakes in young healthy females: a randomised controlled trial. Br J Nutr 2016;115(2):262-70

[xi] Williams CM. Effects of Inulin on lipid parameters in humans. J Nutr 1999 Jul;129(7 Suppl):1471S-3S

[xii] Kok N, Roberfroid M, Delzenne N. Dietary oligofructose modifies the impact of fructose on hepatic triacylglycerol metabolism. Metabolism 1996;45:1547-50.