Inulin & Beta Glucan Reduce Body Fat Gain By -50% & -33%! Both Have Similar Effects on the Gut Microbiome, But Only Inulin Appears to Be More Than An Appetite Suppressant

What do these Jerusalem artichokes, agave, bananas, burdock, camas, chicory, coneflower, costus, dandelion, elecampane, garlic,jicama, Leopard's-bane, mugwort, onion, wild yams, yacon and a whole host of other foods have in common? Right! They contain inulin. Whether you will be able to get a whopping amount of 10% inulin in your diet w/out the use of supplements or "enriched" foods, is yet as questionable as how beneficial this actually is for friends of physical culture.

The gut microbiome is not just one of the hottest topics in the (health-)blogosphere, it is also a subject of ongoing research. Research, however, that is, if we are honest, still very much in its infancy. As impressive as the results from the latest studies into the metabolic downstream effects of the administration of fermentable fiber to rodents may be and as obvious as their relation to certain changes in the gut microbiome of the animals may appear - in the end, our understanding of the underlying mechanisms does not allow any reliable prognoses like "double the amount of lactobacilli and you will eventually be able to lose that pouch of body fat you've been carrying around for years now". And yet, if the results from the latest rodent experiments at the Imperial College in London, could be reproduced in humans, I can already foresee that both, the consumption and use of the foods I listed in the caption of the image to the right, as well as related products, extracts and supplements, which contain more or less significant amounts of the naturally occurring polysaccharides, we usually refer to as inulin, will increase in the months and years to come.

Fermentable fiber and the gut-brain-axes: The key to lifelong leanness?

If this is not your first visit to the SuppVersity, you will certainly be aware that the idea of a magic pill (or fiber) that will allow you to eat whatever, whenever and in whichever amounts without having to cope with the metabolic consequences is illusive. When the addition of 10% inulin (or beta glucan) to the diets of 36 male C57BL/6 mice had an "anti-obesogenic" effect, this does not mean that the poor critters who were kept on a hypercaloric high fat (41.8%) diet for 8 weeks did not get obese. What it does mean, though, is that the addition of 10% fermentable (=being food for certain gut bacteria) fiber in the form of

*the producers of these products did not fund or support the study (at least the scientists don't mention that in the respective disclosure ;-)

• inulin from Synergy(TM)*, a fructan based preparation containing both long and short chain
  fructooligosaccharides, or
• beta-glucan from Glucagel(TM)* a highly rich (,80%) barley derived b-glucan preparation

to their otherwise iso-caloric diet (the HFD control contained cellulose) was not without helped to mitigate the negative effects of this diet - a fact the majority of you, of whom I would expect that they are not on a fast-food diet should keep in mind, before they head over to their favorite online supplement vendor and type "Synergy inulin" into the search box.

Figure 1: Effect of addition of 10% fermentable fiber as inulin or beta glucan to the high fat diet of male mice on cumulative weight gain (left), body composition and fatness (middle) and food intake (right) over the course of 8 weeks (data adapted from Arora. 2012)

In spite of that, the results are simply too impressive not to think about their implications in otherwise healthy and even more so previously obese individuals. This is particularly true, because the same microbial changes about which the authors write in a previously published paper from May 2012 that the ...

"[...] increases in both Bifidobacteria and Lactobacillius and a significant increase in short chain fatty acids (SCFA) [went hand in hand with] increase in neuronal activation within the arcuate nucleus (ARC) of animals that received In [inulin] supplementation" (Anastasovska. 2012)

do not (and this is a result of the researchers very latest experiments) simply blunt the rodents appetite. If that was the case, the rodents that received the beta glucan supplemented chow and consumed 12% less energy should have had the most favorable body composition. A cursory glance at figure 1 will yet tell you that this was not the case, though.

Inulin beats beta glucan when it comes to body fat reduction / repression

If we take a closer look a the differential effects of inulin and beta glucan, there yet only one figure that really sticks out and that's the accumulation of fat within the musculature of the animals. The "beautiful marbling" people are looking for in their steaks, however, usually is a harbinger of impeding or even existing skeletal muscle insulin resistance. A muscle fat content above the high fat control (it's certainly a weakness that we don't have a "real" control group on standard rodent chow, here) as Arora et al. observed it in the tissue samples of the beta glucan group, does thus tell you something about its potential usefulness, or rather uselessness of this specific type of fermentable fiber.

Figure 2: Effects of the different types of fermentable fiber on cecal microflora groups (figures are in scientific notation, this means "1E+6" equals 1mio, "1E+9" would be 1 billion etc.; data based on Arora. 2012)

In conjunction with the information about the corresponding changes in the gut microbiome (see figure 2), which appear virtually identical in both groups (specifically the extreme increasesin in both Bifidobacteria (BIF) and Lactobacillius (LAB) really stick out), this does however suggest that the modulatory effect on the composition of the gut flora, or at least the part of it the scientists evaluated in the study at hand, cannot be the only driving force behind the beneficial metabolic effects of inulin.

Inulin or beta glucan? This is not a question... 

While the latter, i.e. inulin, which has by the way been found to directly suppress lipogenesis in a 2011 study by Belgian scientists in a similar HFD rodent model (Dewulf. 2011), appears to be promising for everyone, regardless of whether he or she is poisoning him- or herself with the standard American diet (which is, with its high fat and high carbohydrate content de facto an identical twin of the so-called "high fat diet" in rodent studies), the ingestion of larger amounts of the former, i.e. beta glucan, does at least appear questionable.

If you want to use inulin to your metabolic advantage, you better make sure you get your self a more comfortable place to answer the call of nature - it could call thrice as often! Moreover, large amounts of inulin and other fermentable fiber can induce gastrointestinal distress-

The question is therefore not so much whether it's worth supplementing (it's certainly worth to incorporate some of the initially mentioned foods into your diet, as most of them contain a whole list of other advantageous micronutrients) with inulin or beta glucan - the answer would obviously be inulin - but rather whether it's worth adding larger amounts of inulin to an already healthy diet. And while we cannot answer this question based on the results of the previously cited rodent studies, we could argue that Marwa Zenhom and her colleagues from the Christian Albrecht University in Kiel have already supplied relevant evidence that this would be the case (Zenhom. 2011). After all, the German researchers have been able to show that the PPAR-gamma related anti-inflammatory effects (significant reductions IL-12 secretion in Caco-2 cells and gene expression of IL-12p35, IL-8, and TNFa as well as NF-kB) of oligosaccharides are not (exclusively) brought about by their effects on the gut microbiome, because bacteria simply were not present in their in-vitro study with human Caco-2 cells (cells from the gut lining). Bassaganya-Riera et al. even argue that this effect could be beneficial for IBS patients (Bassaganya-Riera. 2011).

Whether having 10% of your diet in form of inulin, or to make this more conceivable, having 1 tablespoon of plain inulin for every 9 tablespoons of whatever else you eat is either feasible or reasonable, is a whole different story (to put that into perspective: The average inulin intake of Westerners is 1-10g per day (van Loo. 1995). Even 10g would yet only be enough if you ate only 100g of food within 24h!)... and I must forewarn you, if you go by the fecal volume of the mice in the Arora study, it is possible that you will spend >3x more time on the toilette than usual ;-)

References:

• Arora T, Loo RL, Anastasovska J, Gibson GR, Tuohy KM, Sharma RK, Swann JR, Deaville ER, Sleeth ML, Thomas EL, Holmes E, Bell JD, Frost G. Differential effects of two fermentable carbohydrates on central appetite regulation and body composition. PLoS One. 2012;7(8):e43263.
• Anastasovska J, Arora T, Sanchez Canon GJ, Parkinson JR, Touhy K, Gibson GR, Nadkarni NA, So PW, Goldstone AP, Thomas EL, Hankir MK, Van Loo J, Modi N, Bell JD, Frost G. Fermentable carbohydrate alters hypothalamic neuronal activity and protects against the obesogenic environment. Obesity (Silver Spring). 2012 May;20(5):1016-23.
• Astegiano M, Pellicano R, Terzi E, Simondi D, Rizzetto M. Treatment of irritable bowel syndrome. A case control experience. Minerva Gastroenterol Dietol. 2006 Dec;52(4):359-63.
• Bassaganya-Riera J, DiGuardo M, Viladomiu M, de Horna A, Sanchez S, Einerhand AW, Sanders L, Hontecillas R. Soluble fibers and resistant starch ameliorate disease activity in interleukin-10-deficient mice with inflammatory bowel disease. J Nutr. 2011 Jul;141(7):1318-25.
• Dewulf EM, Cani PD, Neyrinck AM, Possemiers S, Van Holle A, Muccioli GG, Deldicque L, Bindels LB, Pachikian BD, Sohet FM, Mignolet E, Francaux M, Larondelle Y, Delzenne NM. Inulin-type fructans with prebiotic properties counteract GPR43 overexpression and PPARγ-related adipogenesis in the white adipose tissue of high-fat diet-fed mice. J Nutr Biochem. 2011 Aug;22(8):712-22.  
• van Loo J, Coussement P, de Leenheer L, Hoebregs H, Smits G. On the presence of inulin and oligofructose as natural ingredients in the western diet. Crit Rev Food Sci Nutr. 1995 Nov;35(6):525-52.
• Zenhom M, Hyder A, de Vrese M, Heller KJ, Roeder T, Schrezenmeir J. Prebiotic oligosaccharides reduce proinflammatory cytokines in intestinal Caco-2 cells via activation of PPARγ and peptidoglycan recognition protein 3. J Nutr. 2011 May;141(5):971-7.