Kidney Stones

Kidney StonesKidney stones are caused by higher levels of calcium, oxalate and uric acid in urine than can be diluted. There are a few different types of kidney stones including, calcium stones, struvite stones, uric acid stones, and cysteine stones (learn more about these below). For the sake of diet, we’re focusing on calcium oxalate stones. For anyone who is at risk of kidney stones or who has a history of oxalate-based stones, there are a few dietary recommendations; note that most people who are not at risk or don’t have a history, this should not be a major concern. It’s also important to note that research suggests that dietary oxalic acid is only 10-15% of the oxalic acid found in urine of individuals who make kidney stones, so diet may or may not affect risk.

Foods/Choices to Include:

  • Maintain adequate hydration (8-10, 8 oz glasses of water daily)
  • Choose mostly unprocessed foods, whole grains, vegetables, fruits, nuts and seeds- more fruits and vegetables may help to inhibit of calcium stones
  • Lemon juice may help to increase citrate levels in urine that may help to offer protective effect against stones
  • Lower sodium foods- fresh fruits and vegetables, whole grains, and minimally processed foods (especially with calcium stones)
  • Lower oxalate foods (for oxalate-based stones or risk of)-
  • Choose calcium-rich foods when consuming foods higher in oxalates to help bind the oxalic acid- low fat/organic dairy, some dark leafy greens, non-dairy milk fortified with calcium

Foods/Choices to Avoid:

  • High sodium foods
  • Highly processed foods
  • Soft drinks- due to phosphoric acid content
  • Foods high in sugar
  • High animal-protein diet (especially for uric acid stones)
  • For oxalate stones:
    • Eat the following in moderation: Sweet potatoes, rhubarb (always cooked), chocolate, spinach, grains, peanuts, beets and beet greens
    • Eat higher-oxalate foods with a source of calcium to help bind the oxalate in the foods

 Types of Kidney Stones:

  • Calcium stones: Most stones are calcium stones in the form of calcium oxalate or calcium phosphate. Dietary factors include high vitamin D, high oxalate levels from food and produced by the liver, history of intestinal bypass surgery and other metabolic disorders can all increase oxalate in the urine.
  • Struvite stones: These stones form as a response to an infection- like a urinary tract infection.
  • Uric acid stones:  These stones can form in people who don’t drink enough fluids or who lose too much fluid- it can also form in people who have a high protein diet or in those who have gout. Genetic factors can also increase risk for uric acid stones.
  • Cysteine stones: These stones form in people with a hereditary disorder that causes kidneys to excrete too much of certain amino acids.