Side Effects of Bioflavonoid Quercetin & Bromelain

Quercetin, a member of the flavonoid family, gives many fruits and vegetables their vibrant color, and quercetin may help protect against cancer and heart disease, according to the University of Maryland Medical Center. Bromelain, on the other hand, is a mixture of enzymes found in pineapples, and is notably effective in reducing inflammation associated with injuries and infection, reports the UMMC. Because quercetin and bromelain may cause side effects or interact negatively with medications, you should not use these supplements without consulting your health care provider.

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Side Effects of Quercetin

Although quercetin is usually considered safe for consumption, you may experience side effects such as upset stomach and headache, states the UMMC. Additionally, some preliminary evidence exists that quercetin may generate a byproduct, which leads to loss of protein function in your body. Moreover, taking very high doses of quercetin -- greater than 1 gram per day -- may interfere with your kidney health. Therefore, the UMMC advises to take repeated breaks from taking quercetin. People suffering from kidney disease and pregnant and breastfeeding women should not take quercetin.

Other Side Effects of Quercetin

Quercetin has been shown to cause changes in bacterial chromosomes during laboratory observations, according to an article published in the “Internet Journal of Medical Update” in 2007. However, the significance of this discovery for humans is still unclear. Pregnant women and nursing mothers should refrain from taking quercetin because of absence of availability of long-term safety data. Quercetin may also interfere with the body's absorption of cyclosporine, a drug, which decreases the activity of the immune system.

Side Effects of Bromelain

The UMMC says that bromelain is generally recommended for no more than 8 to10 days in a row. Bromelain can produce side effects such as excessive menstrual bleeding, vomiting, diarrhea and nausea. Individuals who are allergic to fennel, cypress pollen, papain, carrot, wheat, pineapple, celery or grass pollen may also be allergic to bromelain. People with liver or kidney disease, high blood pressure and bleeding disorders and pregnant women should not take bromelain, advises the UMMC. Bromelain may also increase the bleeding risk during and after surgery, therefore, you should stop taking bromelain two weeks before surgery.

Other Side Effects of Bromelain

Taking high doses of bromelain might elevate heart rate, according to a study published in the May 1978 issue of “Hawaii Medical Journal,”as reported in NYU Langone Medical Center. Bromelain may also slow down your body’s ability to clot blood, and could raise the risk of bleeding when taken with blood-thinning drugs such as clopidogrel, aspirin and warfarin. The UMMC notes that bromelain may increase the absorption of some antibiotics, especially tetracycline and amoxicillin. Furthermore, bromelain might increase the effect of sedative medications such as tricyclic antidepressants, barbiturates, anti-seizure medications and benzodiazepines. Therefore, check with your health care provider before consuming bromelain if you are taking any of these medications.

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