Isomalto-oligosaccharides (IMO) in “sugar-free” syrups – New study: raise blood sugar levels almost as fast as dextrose!

If something sounds almost too good to be true, then … well, unfortunately, it turns out it probably is.

We really don’t like to deliver bad news and we don’t want to be seen as the killjoy either. But today we have to make something very clear and we need to raise your awareness. And we are very sorry for that…

What are isomalto-oligosaccharides (IMOs)?

Isomalto-oligosaccharides (short “IMO”) are fiber-like sweeteners that can be found in e.g. sugar-free syrups and protein bars. They are now also available purely as baking ingredient, either sold as “fiber syrup” or “tapioca syrup” (e.g. like this one) and also as a powder. They have about 60 – 70% of the sweetening power of retail sugar and consist of different sugar oligomers (an oligomer is like a polymer, but much shorter), including glucose and isomaltose.

What’s the problem with IMOs?

It is said that the so-called α-D-(1,6) bonds between the sugar molecules cause that the oligomers can only be partially metabolized and are therefore listed on nutrition labels as dietary fiber and NOT treated as carbohydrates. For example, you’ll read:

“70% dietary fiber and 5% carbs”

Sounds good, doesn’t it? A fabulous low-carb syrup you can use as a sugar-free sweetener without any worries …


According to current studies, IMOs raise blood sugar levels similar to dextrose (pure glucose)!

Two different types of IMO were tested and dextrose served as a control group. Taken on an empty stomach, both IMOs showed no significant difference when regarding their impact on blood sugar levels compared to dextrose. The insulin levels were affected to a slightly lower extent, but were still very high.


Incredible, isn’t it?

That’s a somewhat weird “fiber” if it can raise your blood sugar levels almost to the same extent as dextrose does, don’t you think? But this is unlikely to surprise anybody, because read this:

Interestingly enough, however, the British Food Standards Agency determined already in 2013 that products containing IMOs shall be marked as “not suitable for diabetics” …?.Please click to read the corresponding report in German language

It is really hard to understand the logic behind THIS, in fact, we can’t make head or tail of it:
Just 5g carbs per 100g, but NOT suitable for diabetics. Hey guys, think about it! ?

This information for diabetics can now be found on the corresponding products, as required (or such a smart phrase like this one: “Product xy is a source of glucose”….Uh, come again???). Whoever keeps such a bottle in the kitchen – just take a closer look at it! You may not have realized it up to now. Why should you? After all, it says on the packaging that the product contains “just” 5g carbs and a solid 70% of fiber. So this has to be a low-carb product …

How wrong can one be! Dietary fibers, in particular those specified as prebiotic, are not all the same and some of them are so optimally metabolized by the human body that their impact on metabolism almost equals that of glucose.

✅ By contrast: cellulose-based (insoluble) fiber such as in bamboo fiber, are excreted completely undigested. But before you panic from soluble fiber: this is also true with fiber contained in nut flour (partly soluble, partly insoluble). For those of you who live with diabetes: You’ll notice when checking your blood sugar levels.

✅ Many soluble fibers are metabolized inside the human body only to a very limited extent, very slowly or only at a very late stage of the digestive process, so that the blood sugar level is not affected. In general, dietary fiber is a good thing.

We’ve been observing IMOs for some years now. In the beginning, existing studies were not that clear and, on the whole, however, we found it extremely difficult to understand whether various companies throw a spanner in the works, just for the fun of it, and drag themselves through the courts (if interested, just search Google for Quest Nutrition Law Suit) or whether there are some authorities around making mountains out of molehills (sometimes, that does happen).

Actually, we would have considered IMO to be very attractive as an ingredient. A low-carb sugar substitute that indeed can be both syrupy AND powdery – a feature sorely missed e.g. with erythritol. In addition, this would have been an alternative to inulin (a fructooligosaccharide), that, unfortunately, has a very low digestive tolerance (plainly speaking: it causes bloating and diarrhoea). However, there is one interesting observation relating to the above-mentioned study: the tested IMOs showed only very little adverse effect on the intestinal tract. But this seems to make sense somehow – if IMOs are largely metabolized by the human body in the same way as easily usable carbohydrates, they will also be digested in the same way: quickly and easily. And they spike your blood sugar.

We don’t want to demonise carbs per se – but playing around with incorrect interpretations of nutrition facts is absolutely dangerous!

But just to make this clear: we don’t villainise all foods that contain ‘a few more carbs’ in general. With a calculator at hand or some simple mental arithmetic, you’ll be able to enjoy even as a low-carb dieter quite a bunch of food without any problems, which is not really low in carbs in a strict sense. Take raisins as an example: when eaten plain and consuming tons of them, this might not be a good idea when following a low-carb lifestyle, but 50g of them spread on a slice of low-carb bread yield a yummy currant bread that need not be ashamed of its nutritional values at all. Apart from that, there are lots of different types of low-carb diets around. Depending on your physical activity level, also some refeeds, enjoyed from time to time, may be okay, too – we are all different and each of us pursues different goals, has a different state of health, different needs. But THAT is not really the point of issue here!

The FATAL thing, though, is how such nutrition labels stating ’5g carbs and 70% fiber’ are interpreted by consumers and what, in a consequence, they provoke in them. Imagine a consumer who perhaps suffers from diabetes. Or someone who wants (or needs) to follow a ketogenic diet. Or somebody who’s accurately counting the carbs when on a low-carb diet and has a clear goal in sight – but who would, in this case, count with just 5g carbs instead of …. 50, 60 or 70g!

Beyond that: Assuming that a sweetening agent contains just 5g carbs, you’d not use it sparingly. At worst, you’ll sweeten all of your recipes with it, and, given the fact that pure IMO has just about 60 – 70% of the sweetening power of retail sugar, you’ll most probably add even more IMOs to your ‘lowcarb-ified’ high-carb recipe, though, than the quantity of sugar stated in the original recipe. Please take a careful look at the chart from the study again!

In plain language, that means that your muffin, if sweetened with retail sugar, most probably would have had a lower impact on your blood sugar levels than sweetened with this awesome “low-carb syrup” containing isomalto-oligosaccharides…

Well, words fail us…

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