Oolong tea is one variety of green tea, sometimes referred to as “half fermented” tea, because when it’s made fresh tea leaves are allowed to ferment halfway via the enzyme present in the leaves. Black tea is fully fermented, and green tea is unfermented. Oolong tea contains the same amount of caffeine as green tea, as well as the same polyphenol content, but lacks vitamin C content, according to “Health Effect of Tea and its Catechins,” by Yukiaki Kuroda and Yukihiko Hara. Polyphenols are powerful antioxidants that help neutralize cell-damaging free radicals. Despite this tea’s many health benefits, people may experience a few side effects, some due to its caffeine content.
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If people drink lots of caffeine over a long time period -- including that from oolong tea -- they may experience insomnia, irritability, heart palpitations or dizziness. An overdose of caffeine can lead to headaches, loss of appetite, nausea, vomiting or diarrhea. If people experience abdominal spasms or vomiting after drinking a large amount of tea, they may be suffering from caffeine poisoning, according to University of Maryland Medical Center.
Patients should talk to a health care provider before adding oolong tea to their regimen, especially if they take certain medications, because the tea can possibly interactions with them, according to UMMC. Medicines know to be affected by oolong tea consumptoin are adenosine for irregular heart rhythm; beta-lactam antibiotics; sedatives called benzodiazepines; propranolol and metoprolol used in treating high blood pressure and heart disease; blood thinning medicines including aspirin; chemotherapy; the antipsychotic medication clozapine; ephedrine; lithium or monoamine oxidase inhibitors for depression; oral contraceptives and phenylpropanolamine used in cold medications and weight loss products.
Sensitivity to Caffeine
People with high caffeine sensitivity, the level at which someone feels the effects of the drug, should avoid oolong tea. This sensitivity may cause hives and skin rashes. The caffeine in oolong tea may also interfere with your sleep, and the National Sleep Foundation recommends not consuming caffeine close to bedtime.
Drinking oolong tea may impair a person's iron metabolism, reports Drugs.com. Iron deficiency can lead to anemia, a condition where the blood has an abnormally low number of red blood cells. This condition causes extreme fatigue and can affect your ability to do physical work and affect brain function, explains the Centers for Disease Control and Prevention.
For those women who are pregnant or nursing, they need to limit their intake of oolong tea due to the effects of caffeine, as recommended by the U.S. Food and Drug Administration. Caffeine crosses the placenta and can affect the developing fetus, according to the American College of Obstetricians and Gynecologists. It is associated with some cases of spontaneous abortion, low birth weight and growth retardation.
People with kidney disorders, heart problems, stomach ulcers or anxiety-related issues should avoid oolong tea, advises UMMC. Caffeine affects the kidneys by serving as a diuretic and may worsen incontinence. It also can raise production of stomach acid, which worsens ulcer symptoms. Caffeine also can increase the body's blood pressure and heart rate as well as stimulates the central nervous system.