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?
Both diets promote kidney stones as follows:
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 .
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 .
"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.
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.