Made from the Camellia sinensis plant, green tea is a rich source of antioxidants called flavonoids that may have certain health benefits, including a reduced risk of some cancers and heart disease. But green tea also contains caffeine, which can have negative effects if consumed in excess. How much green tea you should drink each day depends on your health status. Discuss green tea consumption with your doctor to be sure it's healthy for you.
How Much You Should Drink
Harvard Health Publications recommends drinking a few cups of green tea each day to gain its benefits and says that in tea-drinking cultures, 3 cups per day is a normal amount. The University of Maryland Medical Center bases its dosage recommendation on the amount of polyphenols, or active antioxidant compounds, in green tea. It suggests getting 240 to 320 milligrams of polyphenols each day -- the amount in 2 to 3 cups, depending on the brand.
Effects of Overconsumption
In small amounts, caffeine can have positive effects, including a reduced risk of Alzheimer's disease. However, in excessive amounts it can have troublesome side effects including headache, nervousness, sleeplessness, irritability, irregular heartbeat, heartburn, dizziness and confusion. Although the amount of caffeine in green tea varies from brand to brand, MedlinePlus reports that 1 cup provides about 100 milligrams of caffeine. The site recommends not drinking more than 5 cups per day to avoid these negative effects. However, the website also notes that consuming more than 300 milligrams of caffeine per day can lead to osteoporosis because it increases the amount of calcium lost though urine.
If You're Pregnant or Take Medication
Certain populations should further limit their green tea intake or avoid it altogether. MedlinePlus advises pregnant and breast-feeding women to limit their caffeine intake from all sources to 200 milligrams per day. MedlinePlus also warns that people with anemia, anxiety disorders, heart conditions, bleeding disorders, irritable bowel syndrome, diabetes, high blood pressure, glaucoma and osteoporosis should be cautious about green tea consumption because it can worsen their conditions. Further, green tea may interact with numerous medications, including stimulant drugs such as amphetamines, some antibiotics and birth control pills, lithium, estrogen pills and many others. If you are pregnant or breast-feeding, have a health condition or are on medication, check with your doctor before consuming green tea.
Tips for Tea Drinking
If you're sensitive to caffeine, you may be considering switching to decaf green tea. However, Harvard Health Publications notes that decaf varieties contain less of the health-promoting polyphenols responsible for green tea's benefits. If you find drinking caffeinated green tea affects your sleep, registered dietitian Ashley Koff recommends having your last cup eight hours before bedtime to give the caffeine time to wear off. Harvard Health Publications also reports that tea can inhibit your body's absorption of iron from plant foods. Add lemon or milk to your tea or avoid drinking it at mealtime to prevent this.
- University of Maryland Medical Center: Green Tea
- Harvard Health Publications: Benefit of Drinking Green Tea: The Proof Is In -- Drinking Tea Is Healthy, Says Harvard Women’s Health Watch
- AARP: Caffeine for Your Health -- Too Good to Be True?
- MedlinePlus: Caffeine in the Diet
- MedlinePlus: Green Tea
- ShareCare: How Does Caffeine Affect My Sleep?