If you've ever experienced a kidney stone you might think it's the worst pain you've ever had. (Women, you and I both know this is not true...childbirth wins that one. We are warriors!).
Kidney stones, aka renal calculi or nephrolithiasis, are hard deposits of salts and other minerals that form in your kidneys (and sometimes in the bladder) and cause pain when they migrate down the ureter. If the stone blocks the ureter it can cause a back up of the urine (hydronephrosis), spasms, infection and severe cramping pain in the back and groin as it moves through. The pain can be so severe that you can't find a comfortable position and it is difficult to urinate, causing blood in the urine.
There are different types of kidney stones and this is why patients are given strainers in hopes of catching the stone when it is passed so it can be analyzed for type. The types are:
Calcium oxalate and phosphate: Caused by certain metabolic disorders, high doses of vitamin D, some types of high oxalate foods, and certain medications.
Struvite: Caused by urinary tract infections and often quite large
Uric Acid: Caused by dehydration, malabsorption, high protein diets, diabetes and genetics
Cystine: Caused by a hereditary disorder
So here's the new info. Many people with Calcium Oxalate (the most common) and Calcium Phosphate stones think they should restrict calcium intake to prevent stones. A Mayo Clinic study looking at 411 symptomatic kidney stone formers compared to 384 control subjects (no stones) showed lower dietary calcium, potassium, caffeine, phytate and fluid intake were all associated with more stones. Phylate is a naturally occurring compound found in plant foods like beans, grains, nuts and seeds. The researchers controlled for fluid and energy intake and body mass and they found lower dietary calcium and lower potassium were predictive of symptomatic kidney stone recurrence.
If you go online and look up "foods that are bad for kidney stones" you will come up with many "official looking" sites that say avoid calcium, potassium, pickles, caffeine, apricots, avocados, sweet potatoes and many other nutritious foods. THIS IS WRONG
Lets use data to make decisions. If you or your family have had renal stones the evidence shows us:
For Oxalate stones: Limit peanuts, spinach, wheat bran and nuts. These are all high in oxalate.
For all stones: Limit sodium (avoiding canned and processed foods). Limit animal protein ( beef chicken, pork, eggs, shellfish, milk and other dairy products) and switch to a plant based diet.
Get calcium, protein and potassium in foods. Soy, legumes, white beans, parsley, sweet potatoes, beets, seeds, cheese, yogurt, sardines, canned salmon, almonds, leafy greens, figs.
Drink water. Dehydration is a set up for kidney stone formation.