Chemical Make up of Types of Teas

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adam.yusko
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I have a bit more of a personal question.  My uncle really enjoys tea but he also has problems with Kidney stones, one of the things the doctor told him was to cut tea out of his diet completely.  While it has seems to have been working, the question arrises:

 

"Is there a substantial difference in the chemical make up between Black tea and Green tea?"

 

Any papers citing this information would be quite welcome.

 

I told him as they all come from the same plant, it is my belief that the chemical make up between all teas are essentially the same, with only slight variations due to heavier processing removing some of the more fragile components found in green tea.

 

Any help is greatly appreciated.

cinnabar
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calcium oxalate

It would seem logical that the chemical composition of all kinds of tea would be the same, but apparently the levels of calcium oxalate - the substance in foods and beverages that is attributed with increasing the risk for reforming kidney stones - varies considerably between black teas and green teas, because it is affected by metabolic transformation of the tea leaf. The paper entitled "Oxalate content and calcium binding capacity of tea and herbal teas" has a good amount of research on the topic, including some useful charts that show measured oxalate levels of different brewed tea types. Excerpted:

This suggests that the levels of oxalate in the original sprigs are low and that an increase in oxalate occurs in the tissue as a result of the fermentation process used to make black tea. This confirms the suggestion that oxalates are the end product of metabolism in many plant tissues and act as a 'dump system' in the metabolism of the leaf tissue.

 

The level of oxalates found in the green teas consumed in New Zealand are comparable with the values reported for a similar green tea consumed in the USA. The levels of oxalate reported in Japanese green tea are significantly higher (mean 1.48 mg oxalate/g tea).

For calcium stone formers, especially those with elevated urinary oxalate levels, the consumption of green, oolong or herbal teas, or the consumption of black teas with milk, would be a wise recommendation.

The article also discusses how the calcium in milk binds with calcium oxalate in tea, which changes the amount of absorption. But the article also stated that there were studies indicating that rather than increasing the danger of kidney stones, consuming 2-3 cups of tea a day reduced the risk of kidney stones due to the consumption of anti-oxidants and the increase in urinary volume.

And according to this article, the belief in a direct correlation between reducing consumption of calcium oxalates in foods and the risk for kidney stones is controversial to begin with. But it does appear that drinking black tea without milk results in a much greater consumption of calcium oxalates than any other types of tea drinking, and this is what your uncle's doctor is intending for him to avoid.


Cinnabar
Lead Writer, Editor for GongfuGirl.com

adam.yusko
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Joined: 03/13/2010
Thank you very much for this

Thank you very much for this information.  Funny enough after posting this article a tea blog wrote an article about how Rooibos is safe for people with Kidney Stone Problems.

 

I will be sure to forward some of these links to him.

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