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FOS In Probiotics: Good or Bad?

FOS In Probiotics: Good or Bad?

Eating a healthy, balanced diet and getting everything your body needs to thrive is a big ask. Most people struggle to make sure they are getting enough vitamins and minerals, without also having to worry about probiotics and prebiotics. Both are popular topics among nutrition enthusiasts, as the benefits of healthy gut bacteria can’t be ignored.

Probiotics and prebiotics are slightly different but often misunderstood. Probiotics are bacteria that are beneficial to gut health, and they are found in some foods and supplements. While prebiotics are the food that these bacteria live off of, they are a type of carbohydrate which the human body cannot digest.

Prebiotics have been getting a lot more attention recently, but there are both benefits and downsides that you should be aware of. Some probiotic supplements include Fructo-oligosaccharides, or FOS, which is a prebiotic. But are FOS in probiotics good or bad? And which should you choose for a healthy, happy gut?

What Is FOS?

FOS stands for fructooligosaccharides, which is a form of soluble fibre, a water-soluble carbohydrate that cannot be digested by the human body. It is occasionally used as an artificial sweetener in certain foods and is added to some probiotic supplements.

FOS also occurs naturally in some plants, including asparagus, onion, leeks, bananas, garlic and Jerusalem artichoke. When it is used within a probiotic formula, it is designed to work as a nutrient for the healthy bacteria to thrive from. FOS are low-calorie and have a subtly sweet taste which is why they are sometimes used as sweeteners, not only that, but they have no effect on blood sugar levels because they are non-digestible.

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.

What Are The Health Benefits Of FOS?

Fructo-oligosaccharides offer some benefits to overall health and wellbeing and can be an excellent addition to your diet. Not all of these health benefits are proven, but have been reported and studied by health professionals;

They Are Prebiotics

FOS can travel intact through the digestive system through to the colon. Here they can support healthy gut bacteria to grow in the digestive tract, making them a prebiotic. When used in probiotics, they can help the healthy bacteria to flourish.

Protection From Unhealthy Bacteria

Reports have 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.


FOS are noncarcinogenic according to a review from Veterinary and Human Toxicology. This means they are not toxic to animals or humans or linked to cancer.


What Are The Side Effects Of 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;

Abdominal Problems

Some research suggests that FOS can increase digestive symptoms, particularly in those who have a limited tolerance to fructose or lactose. Such symptoms can include increasing cramping, diarrhoea, abdominal bloating and loose stools.

Aggravate IBS

FOS has been researched as a helpful tool for IBS sufferers, with mixed results. Some individuals who suffer from Irritable Bowel Syndrome, or IBS, can have an increased in digestive symptoms following the introduction of FOS.

Bacteria Fermentation

FOS can stimulate all bacteria in the colon, which includes both the good and the bad bacteria. An increase in non-beneficial, or pathogenic, bacteria can increase digestive symptoms within the colon, including bloating, pain and gas.

Should You Take Probiotics With 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, just in case, and focus on choosing hardy, resilient bacteria that doesn’t rely on FOS to thrive in the gut. Udo’s Choice is one such brand, and have chosen to keep FOS out of all of their probiotic formulas, so as to include anyone who is sensitive to FOS.

Udo’s Choice microbiotic (another word for probiotic) blends are carefully designed, with specific strains of bacteria chosen to promote gut health at every life stage. Strains are chosen based on their ability to colonise without the addition of FOS.

Our Super 8 Microbiotics have been designed with a high percentage of Lactobacillius acidophilus and other strains specific for upper bowel health, for those who want to take acidophilus, without forgoing other beneficial bacteria.

For a more general, all-round approach, we also have our Udo’s Choice Adult’s Blend Microbiotics, which is made from 6 adult-specific strains of bacteria. This probiotic formula has been created specifically for healthy adult microflora and contains the appropriate strength for adults.

Children need different probiotics than adults, and our Junior and Infant Blends are designed just for the little ones.

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