Tea is the second most consumed beverage in the world with 2 billion people drinking tea every morning. It is prepared by pouring hot water over crushed leaves of the Camellia Sinensis plant a plant native to China that now grows all over the world. The taste of tea depends on the chemical constituents of the plant which are influenced by the climate and soil conditions of the growing region.
it is therefore disconcerting to hear that such a popular plant has detrimental health effects. Friends, patients and even random strangers seem to think that tea causes many ailments including cancer. Is there some truth? Below are results from a quick scan of published medical literature (mainly pubmed) to determine whether there is any significant scientific research that supports existing beliefs.
Both black and green teas do not contain any significant essential nutrients, except for, manganese at 0.5 milligrams per 8 oz cup representing 26% of the Daily recommended intake (DRI). Tea does contain soluble (caffeine, flavonoids, amino acids) and non-soluble constituents (fiber or cellulose). Caffeine accounts for only 3% of tea’s dry weight which depends on the tea brand, and brewing method. In particular, black tea contains 22–28 milligrams or 0.00078–0.00099 oz of caffeine in 1 gram (0.035 oz) while green tea ranges from 11–20 milligrams (0.00039–0.00071 oz. Tea also contains low amounts of other caffeine-like stimulants e.g. theobromine and theophylline. Tea also contains significant amounts of polyphenols consisting of upto 30–40% (10X more than caffeine) flavonoids, epigallocatechin gallate, and other catechins.
Although polyphenols are considered antioxidants with thousands of anecdotal evidence supporting health benefits in cancer and diabetes among other diseases their specific role in life cannot be established, hence the US Food and Drug Administration (FDA) prohibits the proclamation of health benefits of polyphenols on food labels by enforcing labeling guidelines to manufacturers that state polyphenols cannot be mentioned as antioxidant nutrients unless physiological evidence exists to verify such a qualification and a daily recommended intake (DRI) value has been established.
Therefore, although tea in itself doesn’t appear to cause ill health, the tea plant is a known accumulator of fluorine compounds, which are readily released into tea during cooking. The Fluoride ion in low doses reduces tooth decay (used in toothpaste and water fluoridation). At much higher doses and frequent exposure, fluoride causes health complications and can be toxic.
Hence tea is potentially a vehicle for fluoride overdosing. When contaminated tea is taken without eating, fluoride is completely absorbed (100% of intake). When the contaminated tea is taken with food, only ~60-80% of the consumed amount is absorbed. Of the consumed amount, approximately 50% of the absorbed fluoride is excreted through urination within twenty-four-hours. The remainder is retained in the oral cavity (mouth) and lower digestive tract (intestines).
Consequently, if you consume one liter of tea a day, you can easily reach the daily recommended intake of 4 mg per day. Consequently, poorly processed tea brands can supply up to 120% (4.8 mg) of DRI while fasting (no food) can increase DRI to 150% (6 mg). Tea drinking thus increases the risk of dental coloration and decay (brown teeth) and skeletal fluorosis. This is especially prevalent where intentional water fluoridation (most municipal and tap water) is in effect.
In summary, tea contains many benefits but may also cause detrimental health due to excess fluoride. Hence take tea with caution to maximize on the benefits and decrease associated risks.