Prebiotics - good or bad?

>> Monday, November 3, 2008

One great thing about this blog is that through interacting with other people, I am learning so much. A commenter had a question about fructo-oligosaccharides - an ingredient she saw in one of her food products - and frankly I really didn't know anything about them. Hence this post! I love it when a question spurs me on to learn more about something - especially as I am relatively new to thinking about nutrition and what we put into our bodies in a more hardcore way. 


What is FOS?
So, what exactly are fructo-oligosaccharides (FOS), and what are they doing in our food and supplements? Let's start with the big word - oligosaccharides are short to medium chains of sugar molecules. Adding fructo to the word indicates that the chain is composed of several fructose molecules. So FOS is really just a bunch of fructose molecules connected to each other chemically. (Similarly, galacto-oligosaccharides are a bunch of galactose - or milk sugar - molecules strung together.)

Inulin, often used as a dietary fiber, is a longer chain of fructose molecules. Sometimes inulin is referred to as an FOS, but FOS are generally shorter chains of fructose, while inulin is a very long chain of fructose. Both FOS and inulin are found naturally in Jerusalem artichoke, burdock, chicory, leeks, onion, aspargus, bananas, wheat, leeks, and tomatoes. FOS can be synthesized by Aspergillus enzmatically acting on sucrose or by the degradation of inulin.

FOS actually behaves quite differently than a solitary fructose molecule. We don't have the right enzymes to digest FOS, so they pass through our stomachs and small intestines intact. The flora in our large intestines and colon, however, are able to feed on FOS. What's more, FOS is preferred by the good bacteria (such as the Bifidobacteria and Lactobacillus strains), though bad bacteria (like Klebsiella, Clostridium, and E. coli) are able to digest it on a limited basis. Because FOS serves as food for friendly bacteria (the kind you find in probiotics), it's considered to be a prebiotic. Get it? Prebiotics feed probiotics.

The Good
There are quite a few health benefits associated with FOS. Have you heard that a happy colon equals a happy body? Well, the health and happiness of your colon and intestines is largely dependent on its bacterial population. The human gastrointestinal tract has a complex ecosystem of hundreds of different types of bacteria. These bacteria have enormously important functions, including protection from infection from foreign bacteria and providing nutrients, including B-vitamins and short chain fatty acids.

The good bacteria in our body feed on FOS with a much greater efficiency than the bad bacteria in our body. In that way, FOS acts as a selective food for the good bacteria. The hope with a prebiotic like FOS is that the good bacteria will get the extra nourishment and thrive at the expense of the bad bacteria, and the bacterial population in your gut will then be mostly good bacteria.

FOS consumption has been associated with a lot of positive results. It's been shown to increase calcium and vitamin K absorption in the colon. It also boosts the bacterial populations' ability to synthesize B vitamins (like riboflaven, niacin, and pyridoxine). The level of short chain fatty acids in the colon is also higher with FOS consumption. All good things for colon health.

Because we can't digest FOS, it serves as a low-calorie dietary fiber, and we all know that we need to be consuming more dietary fiber! FOS is sweet - about half as sweet as table sugar - and is finding popularity as a low calorie sweetener, which is one reason why it's popping up in more and more foods.

The Bad
Of course, everything isn't all sunshine and roses with FOS (and inulin). There are concerns surrounding prebiotics. The biggest concern is that FOS also feeds the bad bacteria. If the microflora in a person's gut is out of balance - with more bad bacteria than good bacteria - this could be especially troubling.

Some people who consume FOS have problems with gas formation, bloating, abdominal pain, and (to a lesser extent) diarrhea. These problems have been attributed in part to actions by bad bacteria. While many people tolerate and are benefited by consumption of FOS, others simply cannot tolerate it and experience intestinal havoc when taking FOS or inulin.

Some claim that FOS and inulin can help those with irritable bowel syndrome (IBS), but clinical studies simply do not support this. Not only does FOS not help alleviate IBS symptoms, some IBS sufferers experience a short term worsening of IBS symptoms when taking FOS or inulin.

What's the bottom line?
FOS consumption has a lot of potentially positive outcomes, but its interactions with bacteria in the gut are still not well understood. Each person's body chemistry is so different, and I suspect that the microflora population (good versus bad bacteria) in a person's colon determines to a large extent how effective - or detrimental - FOS is. For a colon in bacterial balance, FOS and inulin are probably beneficial. For a colon where the bad bacteria have an edge, FOS and inulin might not be such a good thing.

FOS is starting to pop up in a lot of different places. If you buy probiotics (aka good bacteria taken as a supplement), you might see FOS bundled in. Inulin is sold as a dietary fiber (Fiber Choice fiber supplement). And because both are sweet, they're starting to be used as sweeteners in foods too.

In the end, we've decided to be cautious with FOS and inulin. We have irritable bowel syndrome in our family and don't want to risk the detrimental effects that can potentially come along with FOS and inulin consumption. So, for now, we'll stick with natural sources of FOS and avoid FOS as a supplement.

Thanks so much for the question, Rachel! I meant for this post to appear much sooner, but life gets in the way sometimes. Keep those questions coming!

18 comments:

James Hubbard, M.D., M.P.H. November 3, 2008 at 6:42 AM  

thanks for the information. I learned a lot from the post.

laura November 3, 2008 at 7:24 AM  

Interesting as always, cathy. You know I'm a big fan of getting fiber from veggies and whole grains, but I occasionally buy pasta with inulin (Dreamfields is the brand) in it--it keeps that pleasant, al dente chewiness just a bit longer, which is nice when you're juggling getting everything on the table.

m November 3, 2008 at 8:17 AM  

A ton of information! thank you!

The Clever Mom November 3, 2008 at 9:27 AM  

Thanks very much!

I'm one of those people who cannot tolerate the FOS/Inulin. Every time I've added it to food, I've spent the next day doubled over in pain from gas production. It may work better if my gut bacteria is in better balance, but my first experiments have scared me off.

fatfighter November 3, 2008 at 9:30 AM  

So far, I haven't had any digestive problems with inulin but I have a couple of friends who do! Thanks for all the great info!

cathy November 3, 2008 at 9:43 AM  

Laura - Interesting. I've never seen pasta with inulin in it. I must admit that I'm a pasta heathen and like my pasta on the mushy side, though.

the clever mom and fatfighter - Inulin doesn't really bother me, but hubby has IBS, so we're steering clear of it. It really does seem to be a body chemistry dependent thing.

Lori November 3, 2008 at 12:13 PM  

Such an interesting and informative post cathy! Thanks! As you could probably guess, I am with you regarding the natural sources.

I'm wondering if they've done any studies looking at the effects/influences of FOS that occurs naturally in foods vs. that in the supplement form.

CarolinaDreamz November 3, 2008 at 5:12 PM  

Hi Cathy. I, too, have been directly avoiding products, when I've felt hit with "FOS" labels. I think history has made me a true skeptic, with my own physical reactions.

I so appreciate learning about this, here. :)
~Heidi

Stan November 3, 2008 at 8:07 PM  

Good article, I haven't seen much discussion on this. I have IBS and fructose issues so I have tried to avoid FOS and products with inulin. It seems like FOS is starting to appear in most of the probiotic blends, however. My probiotic blend (Megafood) lacks it and my herbal stabilizing tablets (IBSuppress) both help. Good luck to all.

MizFit November 4, 2008 at 3:43 AM  

no matter if life gets in the way...just so long as we got this.

VERY INTERESTING and thorough, Cathy!

Erin-Real Tech Mom November 4, 2008 at 6:45 AM  

Wow, very informative! I take a lot of probiotics... maybe i will have to try the prebiotic as well see what happens LOL

ru4real @ Healthy Life November 7, 2008 at 5:08 AM  

I'm new to your blog, but love the information you have here, so I've subscribed to your feed. Thanks for giving us great info in layman's terms.

cathy November 7, 2008 at 7:41 AM  

Lori - I wonder that too. I didn't see any indication of that in my search.

ru4real - Thanks!

And thanks to everyone that commented! Glad you learned something new, and interesting to hear from those of you with personal FOS experiences!

Rachel November 7, 2008 at 8:25 AM  

Sorry I was so slow to read the post! Monday was crazy with Ella and her poor little broken clavicle.

This is good to read. I actually saw the FOS in the new Gerber DHA-fortified baby food. I am feeling so conflicted over all of the fortified baby-foods out there. I am thrilled about the ease of getting some jarred baby foods that are organic and easy to tote along. While I usually make my own baby food for most things, it is nice to have organic options when quick is the order of the day.

But I just don't know what to make of all of the new "fortifications" of the baby foods. DHA seems good, since babies need so much of it...but FOS? (It seems that you can only get the DHA fortified foods with FOS, so the choice is to take them both or none at all.) Hmmm. I just don't know what to even think.

This post has given me a lot of food for thought.

Anonymous January 1, 2009 at 10:17 AM  

Dear Cathe
Very informative in friendly jargon ,the dilemma mankind is confronting is to get enough prebiotic(Soluble Dietary Fibre(SDF))from 100% natural sources , unfortunately all well known natural sources contain a trace of prebiotic ,no real work was done to identify 100% natural source with high conc.per serving, but commercial interests lead to patent-piracy Extracted/processed prebiotic(FOS/Inulin) , which unfortunately gives side effects as usual with man made food/health products.But I have good news for you all , God made Human Milk has the only animal source of prebiotic , that is why infants 0-6month survive only on it . Also God made gum arabic (species Manna as mentioned in three Holy Books and Talha as mentioned in the Holy book Quran)is the only plant source with 85%+ prebiotic , is available only in Sudan (Darfur)to feed the whole world without any side effects. I am ready to supply you and all friends commented up today Free of charge to try for 48hrs only to see the result Happy New Year 2009 , B Rgds MannaMan

His Needs Her Needs September 12, 2011 at 10:48 AM  

Good Work, Cathy! Thanks for taking the time to share all of this. Very useful.

Anonymous August 28, 2012 at 4:51 PM  

Prebiotics do NOT feed bad bacteria. They only feed the good bacteria. Pathogenic bacteria feed on host tissue ONLY. They do NOT eat the prebiotic. I just checked with my nutritionist.

Anonymous August 28, 2012 at 5:00 PM  

Get your inulin from natural sources like Jerusalem Artichokes (not an artichoke but sun flower family)and Krill oil. The krill eat the algae that has inulin.

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