Pu-erh tea, does it contain oxalate?

[Rui]

The urologist has warned me not to drink a lot of black tea as it contains oxalate which helps forming the type of kidney stones I seem to get every few years. He also said that white, yellow and green teas are fine for me to consume.

Although I no longer drink much black tea usually my favourite tea is Pu-Erh in both raw and cooked forms.

Does anyone know if Pu-Erh tea also has high levels of oxalate? Any information on this would be great.

Many thanks.

Rui

[entropyembrace]

I did a quick search of the scientific literature for you and found that post-fermented tea (shu pu-erh and goishi-cha) have the lowest levels of oxalate compared to black tea and green tea. This wouldn't apply to sheng pu-erh unless it's been fermented by aging. (http://www.sciencedirect.com/science/ar ... 7398003409) I should note that a green tea (gyokuro) had the highest levels of oxalates, and sencha was similar to the black teas. The quantity of oxalic acid in the pu-erh was 45.2 mg/L, I don't know if this is a level considered harmful or not to people prone to kidney stones.

Actually the reason why your Dr. would have said that green tea is ok to drink is not that green tea has low oxalate levels compared to black tea, but that the antioxidant properties of green tea are considered to be able to prevent kidney stone formation http://www.sciencedirect.com/science/ar ... 4705608373

I also happened to find probably the best analysis of tea antioxidants I've seen so far here http://pubs.acs.org/doi/abs/10.1021/jf980223x and they tested several pu-erh teas, but they all seem to be fermented and have very low total catechin content. So I would think fermented tea like shu pu-erh and aged sheng wouldnt do anything to prevent kidney stones.

I couldn't find any analysis of the chemical composition of unaged sheng pu-erh, so I can't help you there, sorry

I would think it's more similar to green and white tea than to black tea or fermented pu-erh, but I'm just guessing based on how it looks and tastes.

[Evan Draper]

the antioxidant properties of green tea are considered to be able to prevent kidney stone formation http://www.sciencedirect.com/science/ar ... 4705608373

I'm glad you mentioned that. I am still drinking tea if the anti-cancer and weight-loss properties are overblown. I'm willing to hazard occasional caffeine toxicity. But the specter of uroliths gave me pause.

WILL DRINK MORE SHENG

[bonescwa]

Oxidation isn't required to form a kidney stone of calcium oxalate so i have no idea why an antioxidant would help when they already disparage theories where antioxidant effect makes sense

[entropyembrace]

Oxidation isn't required to form a kidney stone of calcium oxalate so i have no idea why an antioxidant would help when they already disparage theories where antioxidant effect makes sense

In the study above they induced kidney stone formation by feeding the rats ethylene glycol, and in the group of rats which was fed powdered green tea mixed in with their food there was a dramatically reduced formation of calcium oxalate deposits in the renal tubules. The results are really strong that green tea in the diet of the rats did reduce calcium oxalate deposition

The results have also been replicated in other studies such as this one: http://www.biomedcentral.com/1472-6882/13/228

Also the statement that there's no involvement of oxidation in kidney stone formation seems to be wrong...what's your source for that? http://www.ncbi.nlm.nih.gov/pubmed/15499208 says that oxidation damage to kidney cells that work to break down oxalate crystal is involved in kidney stone formation.

[bonescwa]

I don't have a source, I just think that calcium and oxalate will precipitate if their levels are high enough within the kidney. Usually people resorb enough calcium back into circulation that the calcium concentration within the tubule isnt a problem. If they're talking about antioxidants helping the kidney cells to break down the crystals, I assume that the kidney cells are doing it through acidifying the urine so oxalate is excreted unbound. In which case, why are they saying that exogenous antioxidants help kidney cells but the big trend now is that exogenous antioxidants do nothing? it's such bs sometimes

[entropyembrace]

I don't have a source, I just think that calcium and oxalate will precipitate if their levels are high enough within the kidney. Usually people resorb enough calcium back into circulation that the calcium concentration within the tubule isnt a problem. If they're talking about antioxidants helping the kidney cells to break down the crystals, I assume that the kidney cells are doing it through acidifying the urine so oxalate is excreted unbound. In which case, why are they saying that exogenous antioxidants help kidney cells but the big trend now is that exogenous antioxidants do nothing? it's such bs sometimes

The BS is mostly coming from the news media's poor reporting on health studies. There's a general disappointment now that antioxidant's aren't a magic bullet to prevent aging and help us live longer that the same news media and health food industry promoted to us in the past based mostly on some preliminary correlative studies in the 90s and lots of speculation.

What the scientific community is saying is that taking high does of anti-oxidants won't make you younger or slow down the aging process since aging turned out to be much more complex than just oxidative damage accumulating over time. Unfortunately the media turned this into something more like "antioxidants are useless and you're wasting your money" because that makes for snappier news stories.

In the case of green tea and kidney stones there is really strong evidence now that green tea catechins taken orally do help to prevent kidney stone formation. These studies looked at histochemically stained cross-sections of animal kidneys, and found a specific mechanism of action in cell culture. This is much stronger than the correlative studies that just use statistics to say good or bad things about anti-oxidants that the news media likes to report on every time they come out.

The flavour of the month among the poor quality epidemiological studies that the media love so much is to bash antioxidants and get some easy news headlines, but the evidence in favour of green tea catechins in the specific case of kidney stones is from strong cell biology work and shouldn't be dismissed just because some epidemiological studies say general antioxidant intake won't make you live longer or prevent certain types of cancers

[kyarazen]

the biology is probably complicated, off handedly one can think of several competing equilibriums

oxalate binds calcium to give insoluble precipitates (solubility 7mg/litre..ouch!)

polyphenols bind calcium, can possibly shift the equilibrium over time and help dissolve calcium/oxalate precipitates...

polyphenols may appear to affect calcium absorption.. which may decrease the eventual propensity for high calcium levels to be excreted by the kidneys.

[bonescwa]

The fact remains that the mechanism has to be that the catechin does something to a renal epithelial cell that makes the cell do its job better, specifically, helps it acidify the urine if it actually dissolves the stone or just allows the resorption of more calcium from the tubule itself to prevent the stone from ever forming. This sounds like something that would only be controlled by either hormonal or cell surface receptor signaling, the main point is that either of these would require a change in gene expression. cranberry juice is supposed to work just because it acidifies the urine directly, I can understand a simple mechanism like that, but I'm not seeing how green tea is going to change renal cellular physiology. Even endogenous antioxidants don't really do that.

[kyarazen]

The fact remains that the mechanism has to be that the catechin does something to a renal epithelial cell that makes the cell do its job better, specifically, helps it acidify the urine if it actually dissolves the stone or just allows the resorption of more calcium from the tubule itself to prevent the stone from ever forming. This sounds like something that would only be controlled by either hormonal or cell surface receptor signaling, the main point is that either of these would require a change in gene expression. cranberry juice is supposed to work just because it acidifies the urine directly, I can understand a simple mechanism like that, but I'm not seeing how green tea is going to change renal cellular physiology. Even endogenous antioxidants don't really do that.

it doesnt necessarily need to act on the renal tissues directly, the body's made up of a systems of inter-connected equilibriums. if you have some calcium sink in the body, i.e. something that decalcifys and deplete calcium ions in the blood stream, your bone will start dissolving to restore the calcium.

similarly by ingesting green tea, which would bind to calcium and metal ions in the gut, and potentially reducing its absorption into the body, one may be taking in less calcium than required, and may result in equilibrium shifts too.

the way that plants interact with our body will continue to change as we discover more.. just like a couple of years ago, the big hoo-ha on rice micro-RNAs : http://www.nature.com/cr/journal/v22/n1 ... 1158a.html

[Rui]

Thank you very much to everyone who contributed to the answer of my question.

It is very illuminating to hear that it is not just a question of drinking tea or not being a positive correlation to kidney stone formation.

Now I wish I could get hold of some of these papers that have been quoted but it seems they are all charged for. Therefore I am going to buy one or two for me to read probably the ones who are more directly related to Pu-erh.

Thank you once again to everyone.

Kind regards,

Rui

[Guozhiliu1603]

wow Guys ,Thanks for the topic and your knowledge ,Because I am a oxalate patient ,my oxalate ratio very is high ,I am under treatment ,My doctor advice me for not to take much spinach and fiber one cereal ,which I love to eat ,but after your views I most try green tea for reducing my oxalate quantity.

[Balthazar]

Now I wish I could get hold of some of these papers that have been quoted but it seems they are all charged for. Therefore I am going to buy one or two for me to read probably the ones who are more directly related to Pu-erh.

If you know someone studying at a university there's a good chance the person will be able to help you get some (if not all) of these. Just saying, the academic publishing price model really is insane.

[kyarazen]

Now I wish I could get hold of some of these papers that have been quoted but it seems they are all charged for. Therefore I am going to buy one or two for me to read probably the ones who are more directly related to Pu-erh.

If you know someone studying at a university there's a good chance the person will be able to help you get some (if not all) of these. Just saying, the academic publishing price model really is insane.

haha! you can imagine the amount of pu-erh or tea leaves that could be bought for the price of some documents sometimes!

[bonescwa]

The fact remains that the mechanism has to be that the catechin does something to a renal epithelial cell that makes the cell do its job better, specifically, helps it acidify the urine if it actually dissolves the stone or just allows the resorption of more calcium from the tubule itself to prevent the stone from ever forming. This sounds like something that would only be controlled by either hormonal or cell surface receptor signaling, the main point is that either of these would require a change in gene expression. cranberry juice is supposed to work just because it acidifies the urine directly, I can understand a simple mechanism like that, but I'm not seeing how green tea is going to change renal cellular physiology. Even endogenous antioxidants don't really do that.

it doesnt necessarily need to act on the renal tissues directly, the body's made up of a systems of inter-connected equilibriums. if you have some calcium sink in the body, i.e. something that decalcifys and deplete calcium ions in the blood stream, your bone will start dissolving to restore the calcium.

similarly by ingesting green tea, which would bind to calcium and metal ions in the gut, and potentially reducing its absorption into the body, one may be taking in less calcium than required, and may result in equilibrium shifts too.

the way that plants interact with our body will continue to change as we discover more.. just like a couple of years ago, the big hoo-ha on rice micro-RNAs : http://www.nature.com/cr/journal/v22/n1 ... 1158a.html

I was referring to the mechanism from the paper EE described, looking at the stained sections of the kidney tissue, which sounds a lot more complicated than the catechin or polyphenol just binding the calcium itself. For there to be a change in the sections if renal tissue the tea has to causes a change in the cell morphology itself. Lots of things can bind calcium in the gut.