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From Natural News:

Highly acidic diets tend to create an environment which encourages kidney stones, while more alkaline diets help prevent these kind of deposits.

Is this true?

  • When we've had similar questions before it has turned out the proponents were using the term acidic in a non standard way. – Oddthinking Mar 2 '14 at 20:41
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Both diets promote kidney stones as follows:

  • acid diet: uric acid or cystine stones
  • alkaline diet: calcium- and phosphate-containing stones

The formation of various types of kidney stones is strongly influenced by urinary pH. An alkaline pH favors the crystallization of calcium- and phosphate-containing stones, whereas and acidic urine pH promotes uric acid or cystine stones [1].

A low-carbohydrate high-protein diet with its increased acid load results in very little change in blood chemistry, and pH, but results in many changes in urinary chemistry. Urinary magnesium levels, urinary citrate and pH are decreased, urinary calcium, undissociated uric acid, and phosphate are increased. All of these result in an increased risk for kidney stones [2].


References:

  1. Wagner CA, Mohebbi N. Urinary pH and stone formation. J Nephrol. 2010 Nov-Dec;23 Suppl 16:S165-9.
  2. Gerry K. Schwalfenberg. The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health? J Environ Public Health. 2012; 2012: 727630. Published online Oct 12, 2011. doi: 10.1155/2012/727630. PMCID: PMC3195546
  • You say may. The reference says "could". What is the answer? – user5582 Jun 11 '14 at 15:11
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    To be specific, it seems Kessler 2002 establishes the plausibility of Blackcurrent juice being effective, but doesn't establish that the mechanism is in fact due to its alkaline nature. – user5582 Jun 11 '14 at 16:13
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"Alkaline" diet is a wrongly used term, it should be "alkalizing." Alkalizing diet is the diet that alkalizes the urine — it raises the pH of the urine.

Most fruits and vegetables alkalize the urine (even when most fruits are slightly acidic, but note, not acidifying), and most meats and fats are acidifying, probably because of high amino acid and fatty acid content...Acidic urine promotes the growth of calcium-oxalate stones (by far the most common, about 80% of all stones), urate and cystine stones. Alkaline urine promotes the growth of calcium-phosphate stones. NOTE: Calcium-oxalate and calcium-phosphate stones are not the same, so it is not enough to say "calcium" stones...Alkalizing diet can (or may) help prevent stones that grow in acidic urine (calcium-oxalate, urate, cystine), but it can promote the growth of calcium-phosphate stones.

PubMed Central

It is probably potassium in fruits that makes them alkalizing. Here is a list of foods high in potassium (Nutrientsreview.com)

In several studies (see the Linus Pauling Institute link below) high potassium diet was associated with the lower risk of calcium-oxalate kidney stones, but "associated" does not already mean the cause-effect relationship. Also, it is often hard to say, was it potassium, alkalization or some other property of food that prevented kidney stones.

Conclusions:

  • Alkalizing, that is potassium-rich diet, may help prevent calcium-oxalate kidney stones, but more research is warranted. Linus Pauling Institute

  • According to this review (PubMed Central), acidifying, that is high-protein (meat) diet is associated with increased risk of urate kidney stones.

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