Probiotics are live microorganisms that can bring about health benefits. Most are bacteria from the Lactobacillus and Bifidobacterium genera. They are similar to bacteria that occur naturally in the gut and are often referred to as “friendly bacteria” or “good bacteria”.
While the field goes back to the start of the 20th century when Nobel Laureate Eli Metchnikoff studied the health giving effects of fermented milk products, long term clinical trials of many strains used in probiotics are still lacking. In particular there needs to be more focus on their use in the elderly, the young, pregnant women and people with weakened immune system.
Probiotics are identified by genus, species and strain. Each genus (plural: genera) has many species, and within each species there are different strains or varieties. The strain (often trademarked by the manufacture) is what distinguishes it from other strains that are commercially sold. It is at the level of individual strains that the scientific research is applicable.
Side effects of probiotics
- Probiotic side effects tend to be mild and associated with digestion effects such as gas, abdominal pain or bloating.
- There is some concern in the scientific community that certain probiotics may cause bacterial infections that need to be treated with antibiotics. This is particularly the case in people with compromised immune systems.
- Some probiotic strains may also over-stimulate metabolic activity and the immune system causing negative symptoms.
- People with any kind of food allergy should take care when consuming probiotics and seek medical advice before hand. Allergic reactions may include dizziness, rashes, itchiness or swelling around the face or throat and trouble breathing.
- Note that other effects, not listed above, may occur. If you notice any side effects seek the advice of a health professional.
Improved labeling regulations would go a long way in giving consumers the ability to determine for themselves the health benefits or potential side effects associated with a particular probiotic product. In the meantime the guidance below should help as well as this article on identifying the best probiotic supplements.
- When reviewing different products refer to the definition of probiotics provided by the International Scientific Association for Probiotics and Prebiotics and summarized in the diagram on the right.
Products should ideally be sold on the “strain level” linking health benefits supported by clinical studies to that strain (see diagram above for how probiotics should be identified). As a general rule, steer clear of products that don’t contain this information.- Don’t assume that effects from one strain hold true for others. The blending of different strains may also result in different effects. In other words many of the effects are not general effects of probiotics, they can only be attributed to a particular strain or blend of probiotics.
- PubMED and NCCAM offer good resources, guides and sponsored research on probiotics.
- Avoid manufactures who exaggerate the health benefits of their products. For example the FTC recently ruled that there is not enough evidence to support the claim made by Activia the probiotic infused yogurt drink by Dannon that the produce helps to mange constipation.
- Some species such as those used for Acidophilus supplements have a long history of use as probiotics without reports of negative symptoms or side effects, while others are less studied.