Minerals and Kidney Stones: Calcium, Oxalate, Magnesium and Potassium Citrate

Get help first

The NHS (UK) says larger kidney stones can be very painful and need to be checked urgently by a healthcare professional. [1] It lists severe pain, or a high temperature or feeling hot, cold or shivery, as reasons to seek urgent help. [1] In an emergency, use your local emergency number (911 in the US).

The short answer

It surprises many people, but calcium is not the villain. The US National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says that even though calcium sounds like it would cause calcium stones, it does not. [2] In the right amounts, calcium in the digestive tract can block other substances that may cause stones. [2] The picture is different for calcium pills, and the right plan depends on the type of stone, so it is clinician-led.

What the sources found

Calcium and oxalate

In the 1993 men's cohort study, the highest-intake group had lower risk (adjusted relative risk 0.66). [3] This is observational, so it cannot prove cause. [3] Animal protein went with higher risk, and potassium intake with lower risk (relative risk 0.49). [3]

Supplements are another matter. In the Women's Health Initiative trial, women got 1000 mg of elemental calcium as calcium carbonate with 400 IU of vitamin D3 daily or placebo (a study amount, not advice), and kidney stones increased with the combination (hazard ratio 1.17). [4] Because calcium and vitamin D were given together, this trial cannot say which caused the increase. More: calcium supplements, heart disease and kidney stones.

NIDDK says if you have had calcium oxalate stones you may want to avoid some foods to lower oxalate in urine, and that you should talk with a professional about how much. [2] Which stone type you had matters, so ask your clinician. [2] Food oxalate and mineral absorption are covered at plant-based mineral absorption.

Sodium, protein, weight and fluids

NIDDK says drinking enough liquid, mainly water, is the most important thing to prevent stones. [2] Eating more sodium increases the chance of stones, and animal protein may as well. [2] Studies have shown the DASH diet can reduce risk. [2] For uric acid stones, losing weight is especially important if overweight. [2]

Potassium citrate and magnesium

A 2015 Cochrane review of seven trials (477 participants, mostly oxalate stones) found citrate salts prevented new stone formation and slowed growth, but reporting quality was moderate to poor. [6] Dropouts due to side effects were significantly higher with citrate. [6] The American College of Physicians' 2014 guideline recommends, when more fluid fails, a single medicine: a thiazide diuretic, citrate or allopurinol. [5] The guideline frames these as medicine decisions for a clinician to make. The American Urological Association's 2014 guideline likewise says a variety of medications and dietary measures have been evaluated with greater or less rigor for reducing recurrence. [7] Potassium has its own kidney cautions at potassium.

The authors write that urinary magnesium plays an important role in preventing calcium oxalate stones, but the role of magnesium supplements is not clearly defined. [8] The one trial we found had eight patients and measured urine chemistry for seven days, not stone recurrence. [8] Proper evidence not found for magnesium and stone recurrence: we searched PubMed for magnesium and nephrolithiasis trials. Magnesium also has kidney cautions: magnesium.

Gout

Gout is a joint condition, not a stone type, but the NHS lists lifestyle steps such as weight loss, a healthy diet, fluids, and asking a GP about vitamin C supplements. [9] Proper evidence not found for calcium, magnesium or potassium supplements for gout: the NHS page does not mention them, and two PubMed searches for mineral supplements and gout/uric acid returned no results.

Official calcium levels (UK, adults, NHS, 2020)

Adults need 700 mg of calcium a day, and 1,500 mg or less a day is unlikely to cause harm. [10] These are general-population figures; if you form stones, your clinician may set different targets. US and EU figures differ, and we could not read US National Institutes of Health fact sheets this session.