What causes kidney stones and can you prevent them?

Thu, 15 Oct 2009 00:29:22 +0000

Kidney stones will effect around 5 percent of people in at some point in their life, and the rate is growing with time (Parmar 2004). ¹ Significant variation of occurrence exists between sexes; men develop stones twice as often as women at an average age of 30 while for women average age is bimodal with peaks at 35 and 55 (Parmar 2004).² Once you have had one, you also have a very high chance of having another one as there is a re-occurrence rate of 50% over five years (Borghi et al 1996).³ Although there is still somewhat of an evolving consensus around what the main cause is, literature points to treatment resistant micro-bacteria (Çiftçioglu et al 1999) that combines with urine supersaturated with calcium compounds and uric acid (contributed by an individual’s diet), creating the kidney stone (Kajander et al 2003). ⁴ ⁵

An individual’s weight and family history have both been demonstrated to have a positive correlation with his or her risk of getting kidney stones (Taylor et al 2005) (Curhan et al 1997). ⁶ ⁷ However, lack of daily water intake has been demonstrated to be the greatest risk factor, and increasing one’s daily water intake is an easily preventative measure one can take to avoid getting stone’s in the first place (Borghi et al 1996). ⁸ Drinking at least 2.5 liters of water per day has been shown to change the consistency of urine, lowering it’s saturation level of calcium compounds, thereby preventing supersaturation and it’s associated buildups (Borghi et al 1996).⁹ This alone has been found to reduce reoccurred rates of kidney stones from 50% to 20% over a five year period (Borghi et al 1996). ¹⁰

Intake of other fluids have also been found to decrease instances of kidney stones in both sexes. A study by Curhan et al (1998) found the following percentage of occurrence reductions in women for each 240-mL (8-oz) daily serving of the following fluids: caffeinated coffee – 10%, decaffeinated coffee – 9%, tea – 8%, and wine – 59%.¹¹ In contrast, a 44% increase in risk was seen for each 240-mL serving of grapefruit juice consumed daily (Curhan et al 1998). In men the risk of stone formation decreased by the following percentages for each 240-ml (8-oz) daily serving of the following fluids: caffeinated coffee 10%, decaffeinated coffee – 10%, tea – 14%, beer – 21%, and wine – 39%. In contrast, a risk increased 35% for comparable servings of apple juice and 37% for grapefruit juice (Curhan et al 1996).¹²

Reducing one’s consumption of animal protein to less than 52g per day has also been shown to lower one’s risk of specific types of kidney stones (Breslau et al 1988).¹³ Increasing dietary calcium has been shown to lower risk for kidney stones in women (Borghi et al 2002) and men (Curhan et al 1993) and lowering your salt intake to less than 800 mg per day combined with lower intake of animal protein lowers men’s risk of re-occurrence by 18% (Borghi et al 2002).¹⁴ Also, vitamin B6 in doses of >40mg/day has been found to reduce incidences of kidney stones in women (Curhan et al 1999).¹⁵¹⁶ A recent study by Taylor et al (2004) determined that in men: sodium phosphorus, sucrose, phytate, vitamin B6, vitamin D, and supplemental calcium were not independently associated with risk for first time instances, while magnesium intake decreases and total vitamin C intake seems to increase the risk of kidney stones (Taylor et al 2004).¹⁷ While this research may appear to contradict the previous study by Borghi et al (2002), this study examined the combination of reduced salt and animal protein, which suggests that reducing animal protein consumption is a more important dietary change to aid in reduced kidney stone risk.¹⁸

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What causes kidney stones and can you prevent them?