Talk:Green tea

caffeine content

Green tea is a globally important beverage and the encyclopedia should include useful information about its caffeine content. The current article includes a table with nutritional values based on a USDA report. This table does state a number, namely 12 mg of caffeine per 100 g of brew. This number is as good as useless for the following reasons: 100 g of green tea can be brewed with 1,5 g of dry tea leaf or with 6 g of dry tea leaf. Moreover the same amount of dry leaf can be used repeatedly for producing several cups of tea. Caffeine is a well known stimulant which at low dosage is believed to be beneficial to human health, but can be unhealthy if one ingests more than 500 mg per day. Using the USDA number the reader may think that up to 500/12 = 41 large cups of green tea can be drunk per day without ill effects due to the caffeine content, which may be dangerously misleading. I found an official table about the nutrients of Japanese Food which specifies the caffeine content of the most common Sencha variety of Japanese green tea at 2.3 g of caffeine for 100 g of dry leaf (or 23 mg of caffeine per gram of dry leaf). Thus the consumer can calculate that if she uses in total, for example, 5 g of dry leaf per day then no matter how many caps she brews with it she will imbibe at most 115 mg of caffeine, well below the unhealthy level. The Gyokuro variety of Japanese Green tea has more caffeine, namely 35 mg per gram of dry leaf. I couldn't find similar tables for Chinese green tea, but since the plant used is the same the caffeine content is probably similar too. Dianelos (talk) 13:34, 15 November 2017 (UTC)

Dianelos: First, when adding a new topic for discussion, it goes to the bottom of the page; see WP:BOTTOMPOST. The USDA nutrition table used in the article, containing the caffeine content of 12 mg per 100 g, is one of several green tea products analyzed and presented in the USDA tables here, and serves to standardize a representative sample. As there are numerous, uncontrollable variables across users in brewing tea that may affect caffeine content – cultivar and amount of tea leaves used, water temperature, brew time, as examples – it's reasonable to present one in the nutrition table with caffeine data determined by a reliable source such as the USDA. Other than for its stimulatory effects to enhance performance, discussed here, it seems to me your above claim of health benefits is overstated, and the analysis you present depends on too many uncontrolled variables to be discussed clearly in the encyclopedia; see WP:NOTTEXTBOOK, #s 1, 6. If you have a proposal for describing caffeine content in a concise way, you should present it here. --Zefr (talk) 15:04, 15 November 2017 (UTC)

Zefr: My referenced source is the Ministry of Education and Science and Technology of Japan, and is certainly reliable. My reason for adding that information is not about reliability but about usefulness. We know that large quantities of caffeine should not be imbibed; thus the Wikipedia article about caffeine mentions a maximum of 400 mg per day for adults (elsewhere I had read about 500 mg per day, but let me stay with the lower number). So it's important for a consumer to know about the caffeine content of the green tea she actually drinks. As a reader of wikipedia I was looking precisely for that information in the current article but did not find it in a form that is useful. As I explained above the USDA number can be dangerously misleading since the reader may think that imbibing 400/12 = 33 large 100 g cups of green tea per day is OK, which at least in some cases is false. For example a single 100 g cup of gyokuro green tea is sometimes brewed with 6 g of dry leaf (some recipes ask for 2 g per oz) and thus can theoretically have up to 6 x 35mg = 210 mg of caffeine. By informing the reader about the caffeine content in *dry leaf* the reader has a useful metric for computing the upper limit of caffeine she will imbibe and thus make certain she does not overstep the maximum recommended dosage. So, for example, if one uses 6 g of dry gyokuro leaf per day, no matter how one brews it one will not imbibe more than the 210 mg of caffeine that is physically present in the leaf. As for the commercial page I also referenced, it is not dubious but presents (and explicitly quotes) the information from the official Japanese government page. The advantage is that this page is exclusively in English and is more concise since it only includes teas whereas the official page mentions dozens of other foods also. I am not aware that there is a policy prohibiting the use of reliable information in commercial sources and I added that secondary source to make life easier for the reader. Dianelos (talk) 14:43, 16 November 2017 (UTC)

This was your edit: The amount of caffeine and of antioxidants in Japanese green teas varies significantly. For example caffeine content in Sencha green tea is 23 mg per one gram dry weight of leaves, whereas in Gyokuro it is 35 mg per one gram dry weight of leaves.

References

1) The first reference is in Japanese and is too detailed as a table of numbers for English users, as one cannot decipher the desired information. 2) The second reference is from Ippodo, which led me to question the analyses as potentially commercial and not sufficiently objective. 3) Your quantitative statements for caffeine content seem incorrect as "per one gram dry weight"; should this be per 100 g? I also question how relevant this information from two types of Japanese leaves is for the general Wikipedia user, as these teas seem somewhat rare for common green tea consumers. If you can find a more general secondary reference that caffeine content may vary among green tea cultivars, then that would likely be sufficient to state. --Zefr (talk) 18:15, 16 November 2017 (UTC)

Mortality risk

This section states "Daily consumption of green tea is significantly correlated with a lower risk of death from any cause", this is a bold statement and I don't think is a serious one.