Green tea interactions and adverse reactions:
- While drinking over 3 cups of green tea daily, patients should be advised to avoid drugs metabolized by the liver such as acetaminophen.
- According to Schönthal, the following adverse reactions have been reported (59): 34 case reports of hepatotoxicity, tremor, headache, pain, paresthesias, insomnia, palpitations, nausea, dysphagia, flatulence, and bloating.
- According to Schönthal the following interactions have been reported (59): Green tea may reduce absorption of iron supplements, pseudoephedrine, theophylline, aminophylline, warfarin, codeine, atropine, ephedrine, carbinoxamine, dextromethorphan, Lomotil®, and Lonox. Green tea may increase the action of ephedrine, pseudoephedrine, theophylline, aminophylline, and reduce the effectiveness of adenosine, bortezomib, and sunitinib.
- Green tea contains caffeine which is generally recognized as safe by the FDA and AMA but can be dangerous with adverse effects such as high bp, stroke, and arrythmias reported. If more than 1-2 cups of caffeinated beverages are consumed per day, it is prudent to seek physician and/or pharmacist approval of caffeine consumption with any medications or supplements.
- Caution use of whole green tea leaves or powder in patients taking warfarin which may make achievement of therapeutic PTINR difficult. When green tea is consumed in the form of whole leaves, or if it is steeped long enough to contain tannins, vitamin K is generally present in amounts significant enough to counteract the effects of warfarin (60,61), but if green tea is steeped for a short time, and the leaves are not consumed, green tea has very low concentrations of vitamin K (63). Vitamin K levels in coffee and tea were obtained by Booth, SL et al, and vitamin K concentrations were about 0.03 μg/100 mL or less, and according to this source, brewed tea or coffee contains extremely small amounts of vitamin K and is not a dietary source (63).
- Consumption of green tea at a dose of 4-6 cups daily for 6 months (480-960 mg of green tea catechins) has resulted in occasional episodes of toxic hepatitis, and the risk appeared to increase with chronic use (62,64). Caution use of green tea in patients with other forms of hepatitis, liver dysfunction, use of other medications cleared by the liver such as acetaminophen.
- No adverse effect of green tea was found in a 12 week RCT by Nagao, T et al (57). Both the study group and the control group had a low incidence of elevated liver function tests (57).
Chocolate or cocoa consumption and blood pressure:
Cocoa, chocolate, and hypertension: Dark chocolate at a dose of 6.3 to 100 grams daily or equivalent cocoa supplement lowers systolic blood pressure about 2-11 mmHg, and diastolic blood pressure about 1-2 mmHg (66-68,69). The effect of blood pressure lowering wears off 2 days after stopping chocolate intake (68).