Fiber charts and the IBS diet
09/27/06 11:39 AM
Loc: Seattle, WA
The post below is courtesy of Sand, who gave a wonderful reply to a recurring question about fiber charts and their relationship to the Eating for IBS diet. Thank you, Sand!
You've been posting a couple of months longer than I have, so I'm no more expert than you are and I know you've seen the issue of fiber counts in charts and labels come up over and over before just as I have. However, since you want to keep this pot boiling, I'm happy to share my thoughts on this subject once again - and once and for all.
Fair warning to everyone else: This is really long and probably pretty boring. Feel free to skip to the last few paragraphs where I give my conclusion.
Fiber charts are unreliable. There are 4 different sites I've seen people post about either recently or a while back where it's possible to find fiber information about foods:
KTL (the Finnish site Ulrika references)
USDA (gives only total fiber, no breakdown)
GMF (this is Abigail's table)
Northwestern (this is from BobK)
If you compare the same food across all four sites, you will find differences in what they report. For example, KTL reports that 100 grams of potato baked with skin have 0.9 grams of total fiber. The USDA claims it has 2.2 grams of fiber.
Similarly, the KLT tables says that 100 grams of walnuts have 15.9 grams of fiber, only 5 of them water-insoluble while the GMF tables say that 100 grams of walnuts have 6.75 grams of fiber, 3.24 of them insoluble. The USDA says 100 grams of walnuts have 6.7 grams of fiber which brings the USDA in line with the GMF tables.
There are even what appear to be inconsistencies within tables. I know there are (or were) some within the Northwestern chart - Soluble plus Insoluble didn't add up to Total for some foods.
In the KTL chart, 100 grams of pear WITH skin has 3.4 grams of total fiber, 1.8 grams of it Insoluble. At the same time, 100 grams of pear WITHOUT skin has 3.9 grams of total fiber, of which 2.1 is Insoluble. It seems unlikely that peeled pear has more total fiber than unpeeled pear and even more unlikely that peeling a pear increases the amount of Insoluble fiber. (I picked pears to check because it's one of the few foods the Northwestern chart lists as having more Soluble than Insoluble, although the KTL chart and the GMF chart disagree.
Beyond the data discrepancies, there are, as I said, darn few foods in the Northwestern chart that have more Soluble Fiber than Insoluble. The same seems to be true for the KTL and GMF lists insofar as I've checked them and Ulrika's comments about what she's found in the KTL charts bear this out. This says to me that either Soluble Fiber means something different to the chart makers than it does common sense wise or a food with close to a 50/50 split is actually a high Soluble Fiber food.
The bottom line is that I really don't care which explanation is correct. I consider the numbers in the charts irrelevant to Heather's Diet. The Eating For IBS Diet is based on Heather's experience about what works for her and what works for others, along with whatever reliable scientific information is available on IBS and its relationship with food. Considering what I read about people's GI docs on here, I'm frankly amazed that she has managed to find any such information out there at all.
Here's how I think about Soluble Fiber in the context of Heather's approach. Soluble Fiber does two things:
1) provides easy to digest foods so your digestion starts off smoothly rather than roughly
2) creates a gel in your colon so things move along smoothly and your gut has something to grip rather than clenching itself
Think about those two functions when you look for Soluble Fiber foods.
Easy to digest: Look at the foods on Heather's list of Soluble Fiber foods. Then think for yourself about whether it would be easy for *your* tummy to handle. Some people think oatmeal is great; I think it's horrible. I don't think of yellow squash as easy to digest (seeds, skin), but I find butternut squash very digestible. If you are unsure, stick with the obvious - pasta, white bread, potatoes, noodles, white rice - and eat everything else like it's Insoluble fiber.
The gel thing: I have no scientific data on whether any or all of the foods on the Soluble Fiber list make a nice gel. My common sense tells me that most of them would because they're ooey and gluey, although again I would look askance at some of the squashes like zucchini and summer squash - they seem more rubbery.
In conclusion, my take on this is pretty simple:
What the fiber charts and labels say is irrelevant. Heather's Eating For IBS Diet either works for you or it doesn't. Either way, it doesn't matter what nutritionists say about the fiber breakdown of potatoes, walnuts, pears, mushrooms, bananas, or your Great-Aunt Sally's Rutabaga Bread.
Eat the way Heather recommends, tempered with your own common sense about what you can and cannot handle. By this I mean if Heather says don't eat a food, don't eat it. If Heather says a food is Insoluble fiber, treat it like Insoluble fiber. If Heather says a food is Soluble fiber, but you're not sure about it, treat it like Insoluble fiber. If Heather says a food should be okay provided you eat it with a Soluble fiber base, but you don't think you can handle it, don't eat it.
If you feel better doing this, great - stick with it. If you don't feel better, this is not the approach for you and you need to look elsewhere.
The Eating For IBS Diet unquestionably saved my quality of life and may have literally saved my life. I can't begin to thank Heather enough and hope everyone else finds her approach just as successful.
I'd also add a post by Syl about the change to fiber labels that helps explain soluble, insoluble, and functional fiber contents.
In terms of the technicalities of this issue, one big problem is that there simply is no definitive list of accurate fiber contents in foods. All of the nutritional analysis databases in the US are based on the FDA numbers, which the FDA itself acknowledges are incomplete and inaccurate. I've no idea what list the databases outside the US are running off of, but obviously there are even more discrepancies there.
However, when it comes to IBS, I don't think the hard numbers for fiber content really matter, which is a good thing because it means we don't have to worry about fiber in black and white terms. We have a lot of flexibility and shades of gray because HOW we eat matters as well.
Cooking insoluble fiber, pureeing it, chopping it, adding it to soluble fiber, etc. makes a world of difference. It's a far cry from having to do something like watch your glucose numbers if you're diabetic.
The terms 'soluble' and 'insoluble' are just the most accurate indications I can use for what the safe foods and caution foods for IBS have in common. I don't have a better way to title them ('smushy and roughage are what I use to try and give people a clear visual indication).
It also seems to me that, in terms of grams to portion size ratios, the hard numbers for insoluble fiber stack up much more quickly than the numbers for soluble fiber. In other words, if you're looking at a bowl of rice with some steamed veggies in it, the soluble fiber numbers will be lower than the insoluble fiber numbers, even though the portion size of rice is much larger than the portion of veggies in it. For this reason, you're much better off to go by visual assessments instead of numbers from a chart (just look at your dinner - is there more rice on that plate than veggies?).
Safe foods, soluble fiber, and insoluble fiber foods are explained more thoroughly in the books Eating for IBS and The First Year: IBS.
If you're using the
IBS Diet Cheat Sheet, remember that it's just a brief excerpt of info from those books, so it's limited by length in terms of explaining soluble vs. insoluble fiber.
Heather is the Administrator of the IBS Message Boards. She is the author of Eating for IBS and The First Year: IBS, and the CEO of Heather's Tummy Care. Join her IBS Newsletter. Meet Heather on Facebook!