Friendly bacteria that naturally reside in the body promote digestive health, boost the immune system and provide other benefits. Several forms of these ‘’good’’ bacteria are readily available as nutritional supplements and using them might address specific health concerns, though not enough evidence exists in most cases to make any firm conclusions about their benefits. While generally safe for the average, healthy person to take, some concerns surround the use of probiotics in specific instances.

Side Effects

Probiotics generally do not cause any significant side effects. Taking them in larger amounts might produce digestive issues, such as gas and bloating, but they are usually temporary. The University of Maryland Medical Center notes a case report of one individual suffering a severe allergic reaction to prebiotics, a supplement similar to probiotics; this type of reaction is very rare, however.

Concerns for Individuals with Compromised Immune Systems

While probiotics might offer certain benefits for the immune system, they might actually do harm in individuals with compromised immunity. In this case, probiotics might actually cause infections. If you take drugs that weaken the immune system, such as chemotherapy agents or immunosuppressants, or have conditions that suppress your immune function, such as HIV, using probiotics, might do more harm than good.

The University of Michigan Health System notes nine case reports of individuals who had compromised immune function, contracting a severe fungal infection after using the probiotic S. boulardii.

Concerns for Critically Ill Patients

A Dutch study, published in the February 2008 issue of ‘’The Lancet,’ wanted to test the effects of probiotics in preventing infections in patients with severe acute pancreatitis, a condition with a high risk of complications. The mortality rate was actually higher in the treatment group than the placebo group. In this instance, you should not use probiotic supplements. An article published in the London-based ‘’Sunday Times,’’ in November 2008 reports the results of this study led the Dutch Food and Consumer Product Safety Authority to rule these supplements should not be used in any patients in intensive care. The results of this study raise concerns about the use of probiotic supplements in seriously ill individuals.

Individuals with Artificial Heart Valves

The University of Maryland Medical Center reports the probiotic lactobacillus acidophilus might cause a rare bacterial infection in patients with artificial heart valves. If this applies to you, definitely avoid this strain and check with your doctor before using any other type of probiotic.