Proof! Fiber Changes The Brain

In a post last week titled This is Your Brain On Fiber, we presented a mountain of evidence pointing to a very solid link between gut microbiota and brain functioning. And we did this in service of establishing a case between fermentable fiber intake and brain functioning. After all, if fermentable fiber intake is the primary modulator of gut microbiota, then the fiber –> brain link is just a hop, skip, and a jump away.

Well, it looks like that game of hopscotch has concluded.

Just three days after that post, a new study was released, and it’s just what I’ve been waiting for. A collaborative study by the Oxford University psychiatry department and prebiotic manufacturer Clasado has shown, for the first time, that consumption of prebiotic, fermentable fiber can significantly impact the brain by modulating gut microbiota.

The study fed rats either FOS (fructooligosaccharides) or GOS (galactooligosaccharides). And here’s what happened:

In both cases significant effects on the neuronal biochemistry of the rats were demonstrated. These effects are believed to have resulted from changes in the gut microbiota including an increase in bifidobacteria facilitated via the feeding of prebiotics. Brain Derived Neurotrophic Factor (BDNF), an important molecule involved in the development and maintenance of neural cells, increased in the brain after repeated ingestion of prebiotics, compared with rats that did not receive the prebiotics. Additionally, components of the N-methyl-D-aspartate (NMDA) receptor, which have a critical role in brain development, learning and memory, also increased in the rat brain after just two weeks of daily prebiotic feedings.

Those effects were the same ones that were presented in the last post, in studies where microbiota were manipulated through direct introduction of bacteria or through antimocrobial therapies. What was missing was using prebiotic, fermentable fiber as a precipitator of microbial changes. With this study, that is no longer missing. The news report notes that human clinical trials are also underway, and results of those will be released soon.

To those experimenting with high dose fermentable fiber and noticing changes & improvements in mood and cognition: you might not be so crazy after all. In fact, if this study holds true for humans, you may be less crazy than when you started.

With this in hand, we’ve got enough under our belts to confidently pick up where we left off. Stay tuned.

— Heisenbug


23 thoughts on “Proof! Fiber Changes The Brain

  1. Excellent news! I believe that you’ve touched on this before (not able to find it) but what is the best source for FOS and GOS? I’ve notice major differences with RS supplementation but I haven’t seen a way to introduce additional *tooligosaccharides’.

    • GOS seems to be super bifidogenic, but isn’t really found naturally. I don’t see it sold as a supplement much, and I don’t make it a point to get it since it’s not naturally occurring. FOS is found in onion, garlic, leeks, asparagus, jerusalem artichoke, yacon. If you are looking for a concentrated supplemental dose like you have with potato starch, there are quite a few FOS supplements sold online. Some are pure FOS (which is short chain), some are mixed with longer chain inulin. Most studies show good effects between 5g-10g/day of FOS.

  2. Thanks for keeping us updated, and -if we follow through- smart enough to keep following this , For starters one could -not disrupting family traditions too much- add some honey and a spoonful of potato starch to a bowl of (preferably homemade) yogurt.

  3. I came across this study in PubMedn 2010 and saved it
    There was also this narrative of the above report.
    My takeaway was that XOS was more efficient than FOS or inulin. I would like to see some discussion on this.
    I find the recent emphasis on resistant starches very interesting and I like the reasoned efforts on this blog. Thanks

    • Thanks for the link, Tom. I hadn’t seen that study. All oligosaccharides are going to have good fermentative potential. There isn’t much info on XOS content in foods, unfortunately. This study graph suggests XOS isn’t quite as good as FOS at stimulating Bifido and Clostridia fermentation. But who knows. I don’t know that it’s really worth the time worrying about which oligo outdoes another. If XOS has an anti-diabetic effect, it probably means all oligosaccharides do.

  4. One of the experiences I have had since adding potato starch into my daily regimen has been weird emotions, especially noticeable during night time waking. I have been getting short flashes of strong emotions some as short as 20 seconds, some as long as 2 minutes, and not apparently attached to any thoughts at the time. With the longer emotional flashes my brain then goes looking for a thought to attach itself to. With the shorter ones I can just observe them in a detached sort of way.

    It makes me wonder how much of my granddaughter’s anxiety is because of her psyche and how much is due to her gut bacteria.

    • “…how much of my granddaughter’s anxiety is because of her psyche and how much is due to her gut bacteria.” I have to say it’s getting harder for me to distinguish the two. I don’t think it’s two, disparate systems. It’s looking more like one system from different perspectives.

      • I am sure you are right, it is just one system. However the issue of causality remains. I think she is anxious because of her gut bacteria, not anxious because of what she is thinking. Modern medicine and psychotherapy assumes anxiety comes from consistent thought patterns and treats it that way. If it is due to gut bacteria our approach to change is quite different.

    • Yes, that’s completely fine. They are both important sources of fermentable fiber. Studies show they have complementary effects. I definitely recommend getting fiber from different sources, not just relying on one type.

    • I’m not an expert and others might have different opinions, but my experience suggests a benefit to keeping types of fiber separate. For example, having a separate FOS supplement, a separate inulin supplement, a separate RS supplement, etc. For me, the reason is that each type of fiber has unique effects, and it helps to time those effects for certain parts of the day.

      For instance, inulin gives me gas. Ridiculous gas. FOS does not. There are days, therefore, that I need to skip inulin for social reasons, but I can take a separate FOS supplement. On the other hand, I cannot take FOS at night because I wake up at 4:30 am and cannot go back to sleep. Inulin and RS do not have that effect on me – in fact, they seem to make me sleep much better. Being able to adjust each type has been very useful. I take the NOW Nutraflora FOS supplement. I have avoided the supplements that put inulin and FOS together.

      Maybe I am doing this wrong, but I am trying to get as much natural fiber as I can from whole plant sources. Vegetables, beans, lentils, etc. I can only get about 75 g of fiber per day average this way given the calories I eat. No junk, all good food. I don’t know how to do better. So I supplement about 50 g or so more RS/fiber. I try to supplement what I might be missing from diet. So when I eat lots of onion, I cut back on inulin. When I can find green bananas I reduce RS. etc.

      • Your overall approach sounds like a very good one. Inulin is definitely known to cause more GI distress than FOS, because it is longer chain and ferments much more slowly. The only thing I would say is that, normally, fibers are never really consumed in isolation. Foods high in FOS and inulin almost always have them together. Fast fermenting fibers like RS and FOS are almost always coupled with slower fermenting polysaccharides like cellulose, inulin, etc. This likely has the effect of slowing down overall fermentation, and pushing fermentation of RS and FOS more distally in the large intestine. Which is probably a desirable thing. But if you need to separate them, that’s of course fine. The hope is that people’s guts will eventually adjust and these effects will be less of an issue. We’ll see.

  5. HI all! Newbie here… I was so excited to discover this blog and have gone fully down the rabbit hole for the past few hours. Thank you for this extremely important work! Question: as someone who is intolerant of inulin (for the time being only, perhaps, until microbiome adapts), I am eagerly seeking a list of non-inulin- or low-inulin-containing FOS-rich food sources. Google has failed me in this regard. Can anyone point me in the right direction?

    • Unfortunately, almost all food that contains FOS contains some inulin. In fact, FOS is just a type of inulin (a short-chain version). But I believe foods like jicama and yacon are predominantly short-chain FOS, with not much long chain, so you may want to try those.

      • Totally random, anecdotal observation since introducing an RS protocol to my regimen that *may* be of interest to you and/or your readers: I have had iron deficiency anemia for many years that has been resistant to all dietary and supplemental attempts at remediation. A corollary phenomenon in some individuals (myself included) that is of mysterious etiology but widely reported/acknowledged in the literature is beeturia, which I have reliably used as a yardstick to assess my iron status. After several weeks of this dietary intervention, I had a beet feast that would normally have turned my urine fluorescent fuschia for at least two days under normal circumstances, and lo and behold… not even the slightest shift in hue. Remarkable. I know that the bifidobacteria play a role in ca2+ absorption from the lumen, so the leap to fe is not (that) far-fetched…

  6. Hi Mr. H,

    Maybe you could help me figure out an interesting thing that happens when I ingest any fiber. I find it starts to move things through my body quicker and when I have finished elimination, I find I don’t have any emotions whatsoever. I feel utterly blank for anywhere between 10 -20 minutes. Things return to normal however this happens every time in take in added fiber or probiotics of any kind. Do you have any idea what is happening to me?

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