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I'm also a member of another forum on a fitness related site, and the discussion came up about concerns surrounding a diet with a relatively high protein intake and the increased 'risk' of kidney stones. I myself, thought with to be true to some degree, to begin with, with all the hype around against atkins/low carb diets. so took myself off and did some research in the area. This is what I found - no longer a cause for concern I believe;
Article from the BMJ (British Medical Journal):
Kidney stones affect up to 5% of the population, with a lifetime risk of passing a kidney stone of about 8-10%.1 Increased incidence of kidney stones in the industrialised world is associated with improved standards of living and is strongly associated with race or ethnicity and region of residence.2 A seasonal variation is also seen, with high urinary calcium oxalate saturation in men during summer and in women during early winter.3 Stones form twice as often in men as women. The peak age in men is 30 years; women have a bimodal age distribution, with peaks at 35 and 55 years. Once a kidney stone forms, the probability that a second stone will form within five to seven years is approximately 50%.1
Kidney stones are broadly categorised into calcareous (calcium containing) stones, which are radio-opaque, and non-calcareous stones. On the basis of their composition, stones are classified as shown in the table. The figure shows multiple calcium oxalate stones.
Recent evidence indicates that formation of kidney stones is a result of a nanobacterial disease akin to Helicobacter pylori infection and peptic ulcer disease.4 Nanobacteria are small intracellular bacteria that form a calcium phosphate shell (an apatite nucleus) and are present in the central nidus of most (97%) kidney stones and in mineral plaques (Randall's plaques) in the renal papilla. Further crystallisation and growth of stone are influenced by endogenous and dietary factors. Urine volume, solute concentration, and the ratio of stone inhibitors (citrate, pyrophosphate, and urinary glycoproteins) to promoters are the important factors that influence crystal formation. Crystallisation occurs when the concentration of two ions exceeds their saturation point in the solution.
A precise causative factor is not identified in most cases. A family history of kidney stones (increases risk by three times), insulin resistant states, a history of hypertension, primary hyperparathyroidism, a history of gout, chronic metabolic acidosis, and surgical menopause are all associated with increased risk of kidney stones.5-11 In postmenopausal women, the occurrence of kidney stones is associated with a history of hypertension and a low dietary intake of magnesium and calcium.12 Incidence of stones is higher in patients with an anatomical abnormality of the urinary tract that may result in urinary stasis (box 1). Most patients (up to 80%) with calcium stones have one or more of the metabolic risk factors shown in box 2, and about 25% of stones are idiopathic in origin. Box 3 shows the various drugs that increase the risk of stone disease.
Summary points >>>>>>>>>>
Calcium oxalate (alone or in combination) is the most common type of urinary stone
Low urine volume is the most common abnormality and the single most important factor to correct so as to avoid recurrences
Risk of a recurrent stone is about 50% within five to seven years
Diets low in salt (< 50 mmol/day) and animal proteins (< 52 g/day) are helpful in decreasing the frequency of recurrent calcium oxalate stones
Low calcium diets are not recommended to prevent recurrent stones, as they increase urinary oxalate excretion and may result in negative calcium balance
Most ureteral stones under 5 mm pass spontaneously
Kidney stones -- Parmar 328 (7453): 1420 -- BMJ
Article from the BMJ (British Medical Journal):
Kidney stones affect up to 5% of the population, with a lifetime risk of passing a kidney stone of about 8-10%.1 Increased incidence of kidney stones in the industrialised world is associated with improved standards of living and is strongly associated with race or ethnicity and region of residence.2 A seasonal variation is also seen, with high urinary calcium oxalate saturation in men during summer and in women during early winter.3 Stones form twice as often in men as women. The peak age in men is 30 years; women have a bimodal age distribution, with peaks at 35 and 55 years. Once a kidney stone forms, the probability that a second stone will form within five to seven years is approximately 50%.1
Kidney stones are broadly categorised into calcareous (calcium containing) stones, which are radio-opaque, and non-calcareous stones. On the basis of their composition, stones are classified as shown in the table. The figure shows multiple calcium oxalate stones.
Recent evidence indicates that formation of kidney stones is a result of a nanobacterial disease akin to Helicobacter pylori infection and peptic ulcer disease.4 Nanobacteria are small intracellular bacteria that form a calcium phosphate shell (an apatite nucleus) and are present in the central nidus of most (97%) kidney stones and in mineral plaques (Randall's plaques) in the renal papilla. Further crystallisation and growth of stone are influenced by endogenous and dietary factors. Urine volume, solute concentration, and the ratio of stone inhibitors (citrate, pyrophosphate, and urinary glycoproteins) to promoters are the important factors that influence crystal formation. Crystallisation occurs when the concentration of two ions exceeds their saturation point in the solution.
A precise causative factor is not identified in most cases. A family history of kidney stones (increases risk by three times), insulin resistant states, a history of hypertension, primary hyperparathyroidism, a history of gout, chronic metabolic acidosis, and surgical menopause are all associated with increased risk of kidney stones.5-11 In postmenopausal women, the occurrence of kidney stones is associated with a history of hypertension and a low dietary intake of magnesium and calcium.12 Incidence of stones is higher in patients with an anatomical abnormality of the urinary tract that may result in urinary stasis (box 1). Most patients (up to 80%) with calcium stones have one or more of the metabolic risk factors shown in box 2, and about 25% of stones are idiopathic in origin. Box 3 shows the various drugs that increase the risk of stone disease.
Summary points >>>>>>>>>>
Calcium oxalate (alone or in combination) is the most common type of urinary stone
Low urine volume is the most common abnormality and the single most important factor to correct so as to avoid recurrences
Risk of a recurrent stone is about 50% within five to seven years
Diets low in salt (< 50 mmol/day) and animal proteins (< 52 g/day) are helpful in decreasing the frequency of recurrent calcium oxalate stones
Low calcium diets are not recommended to prevent recurrent stones, as they increase urinary oxalate excretion and may result in negative calcium balance
Most ureteral stones under 5 mm pass spontaneously
Kidney stones -- Parmar 328 (7453): 1420 -- BMJ
