Excessive tofu causes kidney stones?

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ThinkAboutThis
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Excessive tofu causes kidney stones?

Post by ThinkAboutThis »

I eat a lot of tofu, one could say I'm an addict, but does it actually cause kidney stones?

http://www.telegraph.co.uk/news/worldne ... China.html
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brimstoneSalad
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Re: Excessive tofu causes kidney stones?

Post by brimstoneSalad »

Great yellow journalism clickbait headline there. :roll:

Formation is largely due to not drinking enough water, in conjunction with genetics, but it's worth understanding how they form: it all comes down to solubility.

When a solution is concentrated (due to not being diluted enough with water), crystals precipitate out. There are many kinds of kidney stones, formed from organic and inorganic salts and minerals.

FYI, Chinese drink spectacularly little water, and consume a huge amount of salt (which makes the solution more concentrated too). It's even worse in desert areas in the Middle East where people often suffer from dehydration (their kidney stones are mainly from uric acid formed from purines in meat, and up to 25% of the population suffer from them).

From the article:
The unusually high number of stones was attributed to the high concentration of gypsum tofu, a popular local food, in Mr He's diet. The tofu contains calcium sulphate, which cannot be expelled from the body without a sufficient intake of water.
Even if this is true (I'm skeptical), it's not caused by tofu, it's caused by the high calcium mineral concentration in that particular kind of tofu, from the gypsum (Calcium Sulfate), AND dehydration.
You probably eat less tofu and drink more water than Mr He. You probably also consume less salt and sugar than He does. Your tofu probably also contains less Calcium Sulfate than the local preparation of street tofu in Zhejiang. Mr. He also probably has a genetic condition that makes him predisposed to getting Calcium stones. AND he probably eats a lot of spinach or something rich in oxalates (as many Chinese vegetables are), in addition to tea (which also promotes stone formation due to oxalate content).

If you're worried about it, you can stick to tofu made with glucono delta lactone instead of calcium sulfate or magnesium chloride. I wouldn't worry about it, though.

It's just so highly unlikely, unless you have a family history. Also note that even Mr. He was fine. Stones are uncomfortable, but not really life threatening in the developed world.
https://en.wikipedia.org/wiki/Kidney_stone#Epidemiology

Pretty much nobody dies from this. It hurts (a lot, you'll think you're dying), you go to the hospital, they get them out, you go home. And maybe next time you drink more water, or cut down on the salt a bit, reduce sugar consumption, cut back on the spinach, or reduce your supplemental calcium intake a little, etc.

You don't eat any animal products, so you should already be at a low risk. That's the first thing people with stones need to reduce.
Wikipedia wrote:Risk factors
Dehydration from low fluid intake is a major factor in stone formation.[7][11]

High dietary intake of animal protein,[7] sodium, refined sugars, fructose and high fructose corn syrup,[12] oxalate,[6] grapefruit juice, and apple juice may increase the risk of kidney stone formation.[11]
[...]

In the early 1990s, a study conducted for the Women's Health Initiative in the US found that postmenopausal women who consumed 1000 mg of supplemental calcium and 400 international units of vitamin D per day for seven years had a 17% higher risk of developing kidney stones than subjects taking a placebo.[22] The Nurses' Health Study also showed an association between supplemental calcium intake and kidney stone formation.[6]

Unlike supplemental calcium, high intakes of dietary calcium do not appear to cause kidney stones and may actually protect against their development.[6][22] This is perhaps related to the role of calcium in binding ingested oxalate in the gastrointestinal tract. As the amount of calcium intake decreases, the amount of oxalate available for absorption into the bloodstream increases; this oxalate is then excreted in greater amounts into the urine by the kidneys. In the urine, oxalate is a very strong promoter of calcium oxalate precipitation—about 15 times stronger than calcium. A 2004 study found that diets low in calcium are associated with a higher overall risk for kidney stone formation.[23] For most individuals, other risk factors for kidney stones, such as high intakes of dietary oxalates and low fluid intake, play a greater role than calcium intake.[24]
Supplemental calcium, even in enormous amounts of a whole gram a day, only contribute 17% to increased risk over seven years. Oxalates and other factors are much more significant.

I looked into this more, and found other sources that confirm my claim that he was not drinking water:

http://dailynews.sina.com/gb/news/int/b ... 12925.html
大陆浙江一名男子肾结石开刀,结果医生为他进行了两个小时的手术,取出 420颗小结石。

  医生表示,他执业多年,从未见过这么夸张的结石,主要原因还是这名何姓病患不常喝水,又超爱吃豆腐,使得钙的摄取过多,无法透过排尿排出,因而造成肾结石。

  这名何姓男子说,上个月因为腰痠不已,因此去看医生,经过电脑扫描,发现他左边的肾布满了结石,因此赶紧安排手术,医生说,若是再拖久一点,恐怕整个肾都要切除。

  不过这名男子的肾结石数量远低于世界纪录保持者,根据金氏世界纪录,2009年印度一名医生为病患取出17万2155颗结石。
"Doctors said his practice for many years, had never seen such exaggerated stones, the main reason he named the name of the patient seldom drink water, but also super love to eat tofu, so that excessive intake of calcium, can not be discharged through urination, thus caused by kidney stones."

I haven't been able to find any credible information suggesting the chemical composition of the stones. The doctors probably just assumed.

Anyway, regardless of the composition, the MAIN reason is that he didn't drink water, not due to the tofu. Other sources suggest the man was apparently instructed by his doctors to drink more water, he said he doesn't like to drink water.

Good going yellow journalists for reporting on kidney stones caused primarily by dehydration as caused by tofu. You can see the comments of that Telegraph article are filled with people saying how this proves tofu is bad and everybody should eat meat, etc.
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ThinkAboutThis
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Re: Excessive tofu causes kidney stones?

Post by ThinkAboutThis »

Solid response, thanks. The part that you cited from the article was actually the part which struck my attention, and yes, my mother has had kidney stones removed in the past which made it quite concerning.
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brimstoneSalad
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Re: Excessive tofu causes kidney stones?

Post by brimstoneSalad »

ThinkAboutThis wrote:Solid response, thanks. The part that you cited from the article was actually the part which struck my attention, and yes, my mother has had kidney stones removed in the past which made it quite concerning.
I added a little more.

What were the stones? Composition of kidney stones can be very different. Were they Calcium, Magnesium, Uric Acid?
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ThinkAboutThis
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Re: Excessive tofu causes kidney stones?

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I'm not quite sure what form her kidney stone was, I'll ask her next time I see her. Are you wondering if it's a calcium formed stone?
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brimstoneSalad
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Re: Excessive tofu causes kidney stones?

Post by brimstoneSalad »

ThinkAboutThis wrote:I'm not quite sure what form her kidney stone was, I'll ask her next time I see her. Are you wondering if it's a calcium formed stone?
Yes, Calcium (Calcium oxalate?), or Struvite (Magnesium), or Uric acid stones. If it's calcium based, you may have a genetic predisposition. If it's uric acid you're probably in the clear. I think Magnesium based stones are rarer in humans, but can come from an alkaline pH in the urine (IIRC).

Anyway, the main cause of calcium stones (at least that you'd worry about) is going to be not drinking enough water, eating too much salt, and consuming too much Oxalic acid.
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