fructooligosaccharides in probiotics
Friday, 20 August, 2021

Fructooligosaccharides In Probiotics: Good or Bad?

The benefits of a healthy gut can’t be ignored — just talk to any nutrition enthusiast. As such, probiotics and prebiotics are sky-rocketing in popularity.

Probiotics and prebiotics are often misunderstood. Probiotics (sometimes called microbiotics) are foods or supplements that contain a source of live, beneficial bacteria; prebiotics, instead, provide sustenance to these bacteria. The human body cannot break down prebiotics.

As more and more people opt for a probiotic supplement to give their gut flora a quick, convenient helping hand, prebiotics have been getting more attention, too. This is because some probiotic supplements include a type of prebiotic, such as fructooligosaccharides — or FOS.

When it comes to prebiotics, there are both benefits and downsides that you should be aware of. So, what’s the verdict on FOS? If I want the healthiest, happiest gut possible, should I choose a probiotic with FOS?

What are fructooligosaccharides (FOS)?

Fructooligosaccharides are a form of water-soluble carbohydrate. Composed of short fructose chains, they cannot be digested by the human body. As well as being considered a prebiotic, FOS are commonly used as an alternative sweetener in certain foods and even used as a medicine.

FOS occurs naturally in some plants, including asparagus, onion, leeks, bananas, garlic and Jerusalem artichoke. When used within a probiotic formula, it can serve as sustenance for probiotic bacteria. Because they are non-digestible, they have no effect on blood sugar levels.

While FOS come with their own health benefits, they also have some side effects, which is why probiotics with FOS are not always the best choice for everyone.

What are fructooligosaccharides (FOS) used for?

Because of their ability to act as food for friendly bacteria, FOS often feature in the ingredients list of probiotic supplements. Low calorie and with a sweet taste, FOS are also commonly used as a sweetener; they can even be made into syrups or used as a coffee alternative.

As prebiotics in probiotic supplements

Complex fructooligosaccharides are prebiotics — a type of fibre that our bodies cannot break down, but that bacteria can. FOS pass through our intestines to be digested by our gut microbes; these bacteria then turn FOS into short-chain fatty acids and vitamins.

This is why you’ll often find FOS in probiotic products — those products marketed as containing helpful, beneficial ‘friendly’ bacteria for our bodies.

As an alternative sweetener and food

Fructooligosaccharides are listed as dietary ingredients and can improve food taste and texture. Although they are carbohydrates, they are normally listed as a fibre. Because of their subtle sweet flavour, FOS are often used as a low-calorie sugar alternative.

Some types of FOS are made into syrups — such as blue agave syrup — whereas others can be ground down into a powder and used as a coffee alternative, such as ground chicory root. FOS can be made into extracts of varying concentrations.

As a medicine

Fructooligosaccharides also have some uses in medicine as a treatment for constipation, as well as having been used for treating traveller’s diarrhea, osteoporosis and high cholesterol levels. It is also understood that FOS can aid immunity and bone health.

What foods contain fructooligosaccharides (FOS)?

Fructooligosaccharides occur naturally in many different types of plant:

  • Asparagus
  • Jerusalem artichokes
  • Soybeans
  • Bananas
  • Chicory
  • Onions
  • Garlic
  • Wheat
  • Blue agave
  • Yacon root
  • Tomatoes
  • Leeks

As well as being derived from cane sugar and seaweed, FOS can also be produced in a laboratory.

What are the health benefits of fructooligosaccharides (FOS)?

There are a number of potential known benefits to consuming FOS, spanning their potentially amplifying effects on probiotic bacteria.

Giving probiotics a helping hand

Passing through our bodies, FOS remain undigested until they reach the colon, where they are broken down by bacteria, stimulating their growth and production. This is why they are often included in products that contain beneficial ‘friendly’ bacteria — like probiotic supplements.

Protection from unhealthy bacteria

Research has shown that FOS can help to suppress a toxic bacteria that has been associated with food poisoning, known as clostridium perfringens. It has been claimed that FOS can protect from salmonella and other food-related illnesses.

By stimulating probiotic bacteria, prebiotics like FOS can also indirectly help to prevent the growth of harmful bacteria, keeping your gut flora in harmony.

A balanced gut microbiome is good news for our intestinal immunity, guarding against inflammation and a number of conditions.


FOS are known to increase calcium absorption in the body, which is beneficial to bone health. This may be of particular interest to menopause-aged women — falling oestrogen hormone levels can result in loss of bone mass density, which risks osteoporosis and fracture.

What are the potential side effects and risks of fructooligosaccharides (FOS)?

Incorporating FOS into your diet and choosing probiotics with FOS isn’t all good news — there are also some risks and side effects that you should consider. Some people may have a particular sensitivity to FOS.

Abdominal problems

Research confirms that FOS can increase digestive symptoms, particularly if you have a limited tolerance to fructose or lactose. Even in those who aren’t intolerant, you may notice stomach symptoms similar to irritable bowel syndrome (IBS) when consuming FOS, or probiotics containing FOS.

Increased abdominal symptoms you might report from a FOS intolerance can include:

  • Stomach pain or cramping
  • Diarrhoea
  • Abdominal bloating
  • Abdominal rumbling and noises
  • Flatulence
  • Constipation
  • Nausea
  • Loose stools.

Some people may also experience an allergic reaction to FOS:

  • Puffy, swollen eyes, face or mouth
  • Itchy, red eyes
  • Tingling or itching in the mouth
  • Hives
  • Lightheadedness or fainting

A serious allergic reaction — anaphylaxis — can be fatal. Signs of this can include blue lips or mouth, difficulty breathing, lightheadedness, confusion, throat swelling or collapse. If you experience any signs of an allergic reaction after taking FOS, be sure to contact a doctor immediately.

Aggravation of IBS

FOS has been studied for its impact on those who suffer from IBS. The currently available research shows mixed results; in one study of the impact of FOS in IBS sufferers, treatment with 20g of fructooligosaccharides resulted in worsened symptoms, whereas some patients reported symptom improvement.

It is believed that since FOS are indigestible, large amounts in the colon can provoke gastrointestinal symptoms in those with IBS.

Bacteria fermentation

At present, there is little known research on the potential negative impact of FOS on bad bacteria fermentation. However, as a prebiotic, FOS stimulates ‘good’ bacteria in the colon but, in theory, could also provide fuel for bad bacteria.

In any balanced gut microbiome, there are ‘good’ and ‘bad’ bacteria. As we know, unfriendly — or pathogenic — bacteria can cause dysbiosis (an imbalance of gut flora), risking increased digestive problems like bloating, stomach pain and gas.

So, should you take probiotics with fructooligosaccharides (FOS)?

Probiotics are available with FOS included, with the idea being that they will help the healthy bacteria to thrive. However, there are brands that decide to keep the FOS out of their probiotic formula — to protect those with a FOS sensitivity — and focus instead on choosing hardy, resilient bacteria that doesn’t rely on FOS to thrive in the gut.

Those with a sensitivity or those concerned about digestive symptoms — such as people with IBS — may want to avoid probiotics that contain FOS. If you do choose a probiotic that contains FOS, it is understood that many of the side effects can be mitigated by taking no more than 10g per day.

Choosing the right probiotic supplement for you

One brand who forgo FOS in their probiotics is Udo’s Choice. These blends are carefully formulated with specific strains of bacteria chosen to promote gut health at every life stage, chosen based on their ability to colonise without the addition of FOS.

Udo’s Choice Super 8 Microbiotics is designed with a high percentage of Lactobacillus acidophilus and other strains specific for upper bowel health. For a more general, all-round approach, Udo’s Choice Adult’s Blend Microbiotics is made from six adult-specific strains of bacteria. This formula has been created specifically to an appropriate strength for a healthy adult microflora.

That’s not forgetting the little ones, too — children need different probiotics than adults, which is where Udo’s Choice Junior and Infant blends can come in.

Looking for more insights about gut health and probiotics? Head over to the Inspired Health wellness blog.

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