Are probiotics safe to use?


Lactobacilli and bifidobacteria are commensal and/or indigenous bacteria common to the gut of mammals, including humans.

In addition, these bacteria are always present in our external environments.

Traditional lactic acid bacteria, used for food fermentation, are generally considered safe for oral consumption in the general population – either as part of foods or supplements, and at levels traditionally used. 

Therefore, people who are generally healthy can use probiotics with ease, as they have a good safety record. If any side effects were to present, it’s likely to include only mild digestive discomfort (mainly from gas formation). 

However, in various patient populations, the use of probiotics isn’t safe.

People who are at risk of severe side effects from probiotic use include:

  • Critically ill patients (those in the ICU in hospital) 
  • Post-surgery patients 
  • Very ill infants 
  • People with weakened immune systems (for example, as a result of an auto-immune disease or cancer) 

Cases of septicaemia have been reported in the above patient populations. For this reason, ongoing surveillance remains critical. 

If you suffer from food allergies, you must also be very careful when using probiotics. Make absolutely sure that the probiotic is free from the allergen that you’re allergic to. For example, cow's milk proteins may be present in minute quantities in some probiotic supplements.  

When it comes to the safe use of probiotics, it must be remembered that each genera contains:

  • Many different species 
  • Many different strains

Only the species and strains that have been studied, or which have a long history of traditional use, can be considered safe. 

Pregnant women as well as people with weakened immune systems (e.g. those with HIV/AIDS) or major illnesses (that require hospitalisation) should always speak to their healthcare provider before taking probiotics. Also always consult a doctor before giving a probiotic to a baby.

If you have milk or soy allergy, be very cautious when taking probiotics. Some strains of probiotics may contain milk or soy protein. Check the food label or call the company to be sure. 

Reviewed by Kim Hofmann, registered dietitian, BSc Medical (Honours) Nutrition and Dietetics, BSc (Honours) Psychology. April 2018.

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