A. Introduction.
Tea comes from the plant Camellia sinensis. The plants require 50 inches of rain each year. As with any leaf with a high water uptake, there might be a high accumulation of whatever is in the soil.
"Processing of different types of teas is as follows. [B1]
1. White tea: young leaves or new growth buds, withered, uncured, baked dry;
2. Green tea: steamed or dry cooking in hot pans to prevent oxidation;
dried tea leaves may be separate leaves or rolled into pellets (gunpowder tea);
3. Oolong tea: withering of leaves under sun and warm winds
with further oxidation standard between green and black teas;
4. Black tea: leaves are completely oxidized, withered, and disrupted or macerated
to activate oxidation resulting in catechins being transformed to complex tannins."
The catechins (a form of polyphenol) are thought to be the active ingredients - primarily epigallocatechin gallate (EGCG).
B. Is Tea Safe?
If tea is to have any therapeutic value against PCa, it is likely that a significant number of cups would have to be consumed each day. If the tea contains contaminants, there might be unsafe intake & accumulation.
When buying tea grown in China, it may be worth remembering that the country burns half of the world production of coal. However, tea may be grown in soil that naturally contains toxic minerals.
"Tea plants ... grow in acidic soil {which} may result in excess available aluminum and fluoride" [B1]
[B1] Heavy Metals.
There are 100 PubMed hits for <tea "heavy metals"> & I have cherry-picked this one: (2013 - Canada)
"Common off-the-shelf varieties of black, green, white, and oolong teas sold in tea bags were used for analysis in this study. Toxic element testing was performed on 30 different teas by analyzing (i) tea leaves, (ii) tea steeped for 3-4 minutes, and (iii) tea steeped for 15–17 minutes. Results were compared to existing preferred endpoints.
"Results:
"All brewed teas contained lead with 73% of teas brewed for 3 minutes and 83% brewed for 15 minutes having lead levels considered unsafe for consumption during pregnancy and lactation."
("All brewed tea and tea leaves had detectable lead levels with Chinese oolong teas having the highest levels, followed by green tea and regular black tea having lower levels. Organic white teas had the lowest lead level. Levels ranged from 0.1 μgm/L to 4.39 μgm/L after subtracting the level found after brewing distilled water in fine china cups.")
"Aluminum levels were above recommended guidelines in 20% of brewed teas."
("All teas contained significant amounts of aluminum. Tea leaves contained from 568 to 3287 ng/g of tea. All brewed teas steeped for 3 or 15 minutes contained detectable levels of aluminum. The range was 1131 μgm/L to 8324 μgm/L steeping for 3 minute and 1413 μgm/L to 11449 μgm/L steeping for 15 minutes. Only 2 teas had levels above acceptable limits at 3 minutes of brewing but 6 of the teas had levels greater than the upper acceptable daily limit of 7000 μgm/L. Clearly letting tea steep for longer than 3 minutes is not advisable. Two of the organic green teas had levels above 10,000 μgm/L brewed for 15 minutes.")
"No mercury was found at detectable levels in any brewed tea samples."
("although 18/30 tea leaves had detectable mercury present (as high as 20 ng/g of tea). It appears that the mercury is bound in the leaf in a way that it does not make its way into the brewed tea at levels that are detectable")
"All brewed tea and tea leaves had detectable arsenic with Chinese oolong teas (organic or regular) having the highest levels. Levels in all teas ranged from 0.06 μgm to 1.12 μgm/L of tea steeped for 3 minutes to 0.08 to 1.27 μgm/L of tea steeped for 15 minutes."
"All tea leaves had detectable levels of cadmium. 21 teas had detectable levels after 15 minutes brewing while only 18 teas had detectable levels after 3 minutes brewing suggesting that there is further leaching of this toxicant into the water over time. The highest level was 0.067 μgm/L found in standard oolong tea from China."
"All tea leaves and brewed teas had detectable levels of cesium with one organic tea having 3103 ng/g in the dry leaf, 12.4 μgm/L at 3 minutes of brewing and 16.5 μgm/L at 15 minutes of brewing."
"All tea leaves had detectable levels of tin but only two brewed samples had nonsignificant levels detected in the teas."
"All tea leaves and all teas had detectable levels of barium, antimony and thallium but none had levels considered to be of concern."
"Of the trace minerals manganese is the only mineral found in substantial amounts in teas and some teas will supply more than the total daily requirements. Black tea achieved the highest level in this study. Excess manganese can result in interference with the absorption of iron and may result in ADHD-like symptoms in children exposed in utero."
[B2] Fluoride. There are 318 PubMed hits for <tea fluoride>.
See also: "Foods/Supplements-Vitamins: Iodine & other Halides" for the negative effect of fluoride on iodine status.
[B2a] (2008 - Taiwan]
"Lungjing, pouchong, tienguanyin, oolong, pureh, and black tea specimens were purchased from different counties in Taiwan. Fluoride levels were evaluated in one complete cycle of tea making as well as at different calcium carbonate contents in water, with glass or porcelain teapots, and with/without adding sugar."
"Among six kinds of tea, black tea had the highest fluoride concentrations (8.64+/-2.96 mg/l), whereas pureh (1.97+/-2.70 mg/l) had the lowest levels."
"... intakes of high amounts (> or =5 l/week) of certain tea may result in excess risks of dental or skeletal fluorosis." {5 liters = 10.6 US pints, weekly; = four 6 oz cups daily}
[B2b] (2016 - Ireland)
"The Republic of Ireland (RoI) is the only European Country with a mandatory national legislation requiring artificial fluoridation of drinking water and has the highest per capita consumption of black tea in the world. Tea is a hyperaccumulator of fluoride and chronic fluoride intake is associated with multiple negative health outcomes. In this study, fifty four brands of the commercially available black tea bag products were purchased and the fluoride level in tea infusions tested by an ion-selective electrode method. The fluoride content in all brands tested ranged from 1.6 to 6.1 mg/L, with a mean value of 3.3 mg/L. According to our risk assessment it is evident that the general population in the RoI is at a high risk of chronic fluoride exposure and associated adverse health effects based on established reference values. We conclude that the culture of habitual tea drinking in the RoI indicates that the total cumulative dietary fluoride intake in the general population could readily exceed the levels known to cause chronic fluoride intoxication."
(For members in Ireland: Table 2 identifies the 54 brands & fluoride levels.)
[C] Liver Toxicity & Tea Supplements.
The Life Extension green tea product [C1] claims to deliver "more polyphenols than you get from drinking seven cups of green tea". From personal experience, I can say that it may be unwise to take more than one capsule at a time. Keep an eye on liver enzymes.
-Patrick
[B1] ncbi.nlm.nih.gov/pmc/articl...
[B2a] ncbi.nlm.nih.gov/pubmed/174...