Inulin

What is inulin?

Inulin is an indigestible carbohydrate, a polysaccharide made of 20 to several thousands fructose molecules with a glucose molecule on the end. Inulin belongs to fructans. It is a soluble fiber.

Inulin Digestion and Metabolism

Inulin cannot be digested and absorbed in the small intestine, so it passes to the large intestine where it is broken down (fermented) by beneficial colonic bacteria into gases and short-chain fatty acids (SCFAs) and can provide 1.-2.1 kilocalories per gram ^{[1,2,3,4-p.387]}.

Foods High in Inulin

Picture 1. Examples of foods high in inulin

Foods naturally rich in inulin include wheat, onions, shallots, Jerusalem artichokes, chicory root, leeks, asparagus and rye. Other foods containing inulin: agave, custard apple, mango, peach, persimmon, rambutan, watermelon, zucchini, bananas ^[5,6,7].
Inulin can be added as a fat replacer or fiber to candies, biscuits, cakes, cookies, crackers, frozen dairy desserts, chocolate, ready-to-eat cereals, jams, jellies, reduced-fat milk and soups ^[7].

Inulin Supplements: Insufficient Evidence About Health Benefits

Inulin and oligofructose enriched inulin supplements are available as capsules and chewable tablets.

Constipation. In one study, agave inulin in a dose 5-7.5 grams increased the frequency of bowel movements but also increased abdominal bloating and gas ^[10], so inulin supplements may not be optimal treatment for constipation.

Weight loss. In one study in obese Mexican women, adding 5 grams of inulin to meals for 3 months had no effect on weight ^[12],but according to one systematic review of studies, long-term inulin supplementation may contribute to weight reduction ^[13].

Travelers diarrhea. In one study, inulin in a dose 10 g/day for 2 weeks prior to travel and 2 weeks during travel to countries with increased risk of traveler diarrhea, decreased frequency and severity of diarrhea ^[15].

Diabetes mellitus. In one study, inulin lowered fasting glucose level and glucose spikes after carbohydrate meals ^[8]. In another study, consumption of inulin for 14 days resulted in decreased fasting blood glucose levels in diabetic individuals ^[1,4-p.389].

Cholesterol levels. In some studies, inulin lowered the total and LDL cholesterol ^[8] and blood triglyceride levels ^[2], but in others did not, so more research is warranted ^[1,4-p.389].

Calcium absorption. Inulin may increase calcium absorption but eventual health benefits of this are not known ^[1,4-p.389].

Inulin Is a Prebiotic

Inulin acts a a prebiotic – ingestion of 15 grams inulin per day can stimulate the growth of beneficial intestinal bacteria, especially Bifidobacteria ^{[1,4-p.389;8,11]}. The actual health benefits of prebiotics in humans are not clear yet.

Inulin Supplements Safety

Inulin is Generally Recognized As Safe (GRAS) by the US Food and Drug Administration (FDA) ^[8].

Pregnancy. Do not take inulin supplements during pregnancy or breastfeeding since not enough studies were done to evaluate its safety during these periods ^[14].

Side Effects

If ingested in amounts greater than 20 grams per day, inulin may cause abdominal bloating, cramps or pain, excessive gas (flatulence), loose stools or diarrhea ^[4-p-391;8], especially in individuals with fructose malabsorption or irritable bowel syndrome (IBS).
Fructans might promote dental caries ^[9].

Inulin and Cooking

Physical properties:

Non-sweet
Solubility in water = 10 g/100 mL ^[4-p.387]
Undergoes Maillard browning reaction ^[16]

Related Nutrients

Ninnes KR, 1999, Inulin and Oligofructose: What Are They? The Journal of Nutrition
Roberfroid MB, 2005, Introducing inulin-type fructans PubMed
Elia M et al, 2007, Energy values of macronutrients and specific carbohydrates in foods European Journal of Clinical Nutrition
Mitchell, H., 2006, Sweeteners and Sugar Alternatives in Food Technology
Investigation of Thai Plants as Potential Sources of Fructan and Inulin Main Fractions Asian Institute of Technology
Clinical Ramifications of Malabsorption of Fructose and Other Short-chain Carbohydrates Foodintolerances.org
Novel sweeteners The Sugar Association
GRAS notification for long-chain inulin (lc-inulin) US Food and Drug Administration
Rozen R et al, 2006, The role of fructans on dental biofilm formation by Streptococcus sobrinus, Streptococcus mutans, Streptococcus gordonii and Actinomyces viscosus Wiley Online Library
Holscher CD et al, 2014, Gastrointestinal tolerance and utilization of agave inulin by healthy adults PubMed
Roberfroid, M., 2007, Prebiotics: the concept revisited The Journal of Nutrition
Tovar AR et al, 2012, The inclusion of a partial meal replacement with or without inulin to a calorie restricted diet contributes to reach recommended intakes of micronutrients and decrease plasma triglycerides: A randomized clinical trial in obese Mexican women Nutrition Journal
Liber A et al, 2013, Effects of inulin-type fructans on appetite, energy intake, and body weight in children and adults: systematic review of randomized controlled trials PubMed Health
Inulin WebMD
Cummings JH et al, 2001, A study of fructo oligosaccharides in the prevention of travellers’ diarrhoea Wiley Online Library
Morris C and E, 2012, The effect of inulin and fructo-oligosaccharide supplementation on the textural, rheological and sensory properties of bread and their role in weight management: A review Sheffield Hallam University