Pamela A. Popper, Ph.D., N.D.

Wellness Forum Health

 The incidence of kidney stones is high in the United States and is increasing in Westernized countries all over the world.[1] There are four types of stones, calcium stones, uric acid stones from eating animal foods which are high in purine, struvite stones, usually resulting from kidney infections, and cystine stones caused by a genetic disorder.

There are several causes of stones, most related to diet and lifestyle habits and weight status.  Dehydration is a common cause.[2] While calcium intake from food has been shown to be protective in some studies, calcium and vitamin D supplements increase the risk.[3]

Eating a diet high in animal foods increases the risk of kidney stones as the more animal food consumed, the higher the risk.[4] [5]  One of the reasons is that animal foods are high in purines, which are broken down in the body into uric acid, which can lead to not only uric acid kidney stones, but also gout. Another reason is that high animal protein intake results in higher excretion of calcium, oxalate, and uric acid, which are risk factors for stone formation.[6]

People who have a history of kidney stones usually stop developing them when they increase their water intake, reduce animal food intake, and stop taking supplements.[7]  One study showed that adopting a diet low in animal protein reduced the formation of kidney stones by about 50.0%.[8]

One of the most significant misunderstandings about kidney stones is the role of oxalates in foods in stone formation. Oxalates are salts of oxalic acid, which is found in many plant foods.

Common food sources of oxalates include:

  • Fruits like berries, kiwi, grapes, figs, tangerines, and plums.
  • Vegetables like spinach, Swiss chard, collards, leeks, parsley, celery, green beans, and summer squash.
  • Nuts such as almonds, cashews, and peanuts.
  • Legumes including soy foods.
  • Quinoa, wheat bran, and wheat germ.
  • Cocoa, chocolate, and black tea.

Consuming foods high in oxalate is not harmful for most people, but under the right circumstances oxalates can contribute to kidney stone formation. Normally only 1.0-2.0% of dietary oxalate is absorbed in the gut, but people who have a leaky gut absorb more.  Inflammation in the gut can increase oxalate by as much as 50.0%. A compromised gut microbiome can make even more oxalate available for absorption since beneficial bacteria in the GI tract digest oxalate, preventing most of it from entering the bloodstream.[9] Other factors increasing absorption include dehydration, high blood calcium levels, and high acid load. The body also produces more oxalate when intake of B vitamins and magnesium is low, and vitamin C and fructose intake is high.

Between 80.0% and 90.0% of the oxalates excreted in urine are produced in the body, which means that restricting oxalate-containing foods is not a useful strategy for preventing kidney stones.[10]

Kidney stones can be extremely painful, but most people can prevent recurrence by drinking 64 ounces of water daily, eating a low-fat plant-based diet, avoiding isolated nutrient supplements, and repairing damage to the gut microbiome with probiotics.

[1] Romero V, Akpinar H, Assimos D. “Kidney Stones: A Global Picture of Prevalence, Incidence, and Associated Risk Factors.” Rev Urol 2010 Spring-Summer;12(3):e86-e96

[2] Borghi L, Ferretti P, Elia G et al. “Epidemiological study of urinary tract stones in a northern Italian city.” Br J Urol 1990 Mar;65(3):231-235

[3] See comment in PubMed Commons below Endocrine Society. “Long-term calcium and vitamin D supplement use may be linked to increased risk of kidney stones.” ScienceDaily. 26 June 2012.

[4] Robertson W, Peacock M, Heyburn P et al. “Should recurrent calcium oxalate stone formers become vegetarians?” Br J Urol. 1979 Dec;51(6):427-31.

[5] Curhan G, Willett W, Rimm E, Stampfer M. “A Prospective Study of Dietary Calcium and Other Nutrients and the Risk of Symptomatic Kidney Stones.” NEJM 1993 March;328:833-838

[6] Rao P, Prendiville V, Buxton A, Moss D, Blacklock N. “Dietary management of urinary risk factors in renal stone formers.” Br J Urol 1982 Dec;54(6):578-583

[7] Siener R, Hesse A. “The effect of a vegetarian and different omnivorous diets on urinary risk factors for uric acid stone formation.” Eur J Nutr. 2003 Dec;42(6):332-7.

[8] Robertson W, Heyburn P, Peacock M, Hanes F, Swaminathan R. “The effect of high animal protein intake on the risk of calcium stone-formation in the urinary tract.” Clin Sci (Lond) 1979 Sept;57(3):285-288

[9] Allison M, Cook H, Milne D, Gallagher S, Clayman R. “Oxalate Degradation by Gastrointestinal Bacteria from Humans.” J Nutr March 1 1986;116(3):455-460

[10] Conyers R, Rofe M, Bais R. “Nutrition and Calcium Oxalate Urolithiasis.” In: Schwille P, Smith L, Robertson W, Vahlen-Sieck W, eds. Urolathiasis and Related Clinical Research New York Plenum Publishing Corp; 1985:81-84