Isomalto-Oligosaccharide vs. Fructo-Oligosaccharide




There are many types of oligosaccharide, including

  • Galacto-oligosaccharide (低聚半乳糖),
  • Fructo-oligosaccharide (果寡糖) or FOS,
  • Soybean-oligosaccharide (黄豆低聚糖),
  • Xylo-oligosaccharide(木寡糖), and
  • Isomalto-oligosaccharide (异麦芽寡糖, IMO).


Among the food we eat, burdock, onions, honey, banana, and celery also contain oligosaccharide.

Meiji Seika Kaisha, Ltd. (明治製菓株式会社) is among the first to produce fructo-oligosaccharide (FOS) commercially. Among the 569 “designated health food” by the Japan Ministry of Health and Welfare, 42% contain oligosaccharide.

But oligosaccharides are not all equal. They vary in prices from US$20 to US$100 per 200 gram and also in quality such as degree of purity. Even if two products FOS and IMO are of the same purity, for example 95% concentration, they are still not the same and they behave differently.

Fructo-oligosaccharide (FOS) is the most commonly seen in the market. You may find them added to products like prebiotics or probiotics formula, oat milk powder & etc.

Isomalto-oligosaccharide (IMO) Fructo-oligosaccharide (FOS)
Promote the growth of “good” bacteria. Harmful bacteria cannot utilize IMO. XHarmful bacteria can utilize FOS. Have been shown in some scientific studies that FOS can increase the growth of “bad” bacteria such as Klebsiella Pneumonia, E. Coli and some Clostridium species.
Molecule structure remains stable in gastric acid and bile. XMolecule structure unstable in gastric acid and bile.


  1. FOS are chain polymers of the sugar fructose that are found in a variety of foods. The sugar units can be linked in a single straight chain or can be a chain with side branches. Because the length of the fructose chains can vary from source to source, for example short chains vs long chains, therefore product characteristic can vary according to the mix of FOS content.

    FOS for the most part is non-digestible because the human does not have the enzymes to break down FOS as it travels down the digestive tract. It goes on to stimulate the proliferation of beneficial bacteria in the intestinal tract. But there were studies that have shown that FOS can also encourage the growth of harmful bacteria such as Klebsiella Pneumonia, E. Coli and some Clostridium species.

    IMO, in comparison, cannot be utilized by the harmful bacteria. Prebiotic effect of IMO can be as high as 10 times of FOS, meaning it can take 10 servings of FOS to produce the same number of friendly bacteria as 1 serving of IMO.

  2. Concentration/Purity Level affects GI and Prebiotic Value

    Theoretically speaking, IMO and FOS are digestion-resistant; hence they will not convert to calorie and do not have any GI (glycemic index) value. However, in reality, it is impossible to produce 100% pure IMO or FOS and all products still contain in some varying degree a small amount of glucose. Based on some of the products in the market, for example, a 75% concentration FOS has a GI between 20 to 30 because it still has 25% impurities.

    Therefore, whether you are buying IMO or FOS, you really have to read carefully the fine prints on the label to find out its purity level. Unfortunately, we found that majority of the FOS products in the market do not specify its purity level and many of them are only between 50% to 70% purity level. The same applies to Isomalto oligosaccharide.

Contrary, Happy Oligo® has a 97.5% purity of isomalto-oligosaccharide and an overall prebiotic effect of 95%~99% (97.5%±2.5%), which is the highest concentration possible and it is also safe for normal consumption by diabetics. You can rest assured of quality.


The Glycemic Index (GI)

  • provides a measure of how quickly blood sugar levels (i.e. levels of glucose in the blood) rise after eating a particular type of food.
  • estimates how much each gram of available carbohydrate (total carbohydrate minus fiber) in a food raises a person’s blood glucose level following consumption of the food, relative to consumption of pure glucose.
  • Glucose has a glycemic index of 100.