Guarana berries come from the plant Paullinia cupana, native to South America. People use guarana supplements for increasing energy or losing weight. The active ingredient is caffeine, a central nervous system stimulant. Guarana berries have more caffeine than coffee beans, according to eMedTV. Guarana benefits and bad effects are similar to other products containing high levels of caffeine.
Effects on the Heart
High caffeine intake affects the heart and can worsen existing heart problems, according to eMedTV. An article published in the May 21, 2001, issue of the "Medical Journal of Australia" reported the case of a 25-year-old woman with mitral valve prolapse who developed intractable ventricular fibrillation, a severely abnormal heart rhythm, after consuming a guarana health drink. EMedTV notes that guarana can cause heart palpitations and tachycardia, or a rapid heartbeat. If you have heart problems, do not take guarana supplements without consulting your health care provider first.
Other Health Conditions
Guarana also can aggravate other health conditions due to the caffeine content, explains eMedTV. Caffeine can raise blood pressure, which causes problems for some people with hypertension, particularly for those not used to the substance. Additionally, caffeine can worsen glaucoma. The stimulant effects of caffeine can cause anxiety, calling for caution in people with anxiety disorder. In some patients with psychotic disorders, caffeine makes their symptoms worse.
Side Effects
Caffeine has several common side effects. The substance is a diuretic, so it causes increased urination, notes the Memorial Sloan-Kettering Cancer Center. Because caffeine is a central nervous system stimulant, it can lead to nervousness, restlessness, agitation, anxiety, shakiness, jitteriness, tremors and insomnia. Gastrointestinal effects also are common with heavy intake, including indigestion, heartburn and nausea. Some people experience headaches and ringing in the ears, known as tinnitus. Potential severe side effects with high doses include high blood pressure, rapid breathing and even seizures. An allergic reaction to guarana is possible; the signs are rash, hives, itching, swelling, and difficulty breathing or swallowing.
Drug Interactions
Guarana can cause severe hypertension when combined with monoamine oxidase inhibitors, according to the MSKCC. These are antidepressants commonly called MAOIs. Some examples include isocarboxazid, phenelzine and tranylcypromine. The caffeine content of guarana also can decrease the effects of lithium, used to treat manic episodes of bipolar disorder. Caffeine may increase blood levels of clozapine, an antipsychotic drug, and this could cause harmful side effects. Additionally, the stimulant effects of guarana can be dangerous when taken with other stimulants, such as ephedrine.
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