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Will cranberry juice help with kidney stones?

Kidney stones are hard deposits made up of minerals and salts that form inside the kidneys. Passing these stones can be incredibly painful. This has led many people to explore natural remedies like cranberry juice to treat kidney stones.

What are kidney stones?

Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine. The most common types of kidney stones are:

  • Calcium stones – Most common type, made up of calcium oxalate
  • Uric acid stones – Form when there is too much acid in urine
  • Struvite stones – Less common, often caused by urinary tract infections
  • Cystine stones – Rare, form in people with a genetic disorder called cystinuria

Kidney stones can range in size from a tiny grain of sand to larger than a golf ball. Small stones may go undetected and be passed out painlessly in the urine. However, larger stones can get stuck in the urinary tract. This blocks the flow of urine and causes severe pain.

What are the symptoms of kidney stones?

Common signs and symptoms of kidney stones include:

  • Severe pain in the side and back, below the ribs
  • Pain that spreads to lower abdomen and groin
  • Pain that comes in waves and fluctuates in intensity
  • Pink, red or brown urine from blood in the urine
  • Cloudy or foul-smelling urine
  • Persistent need to urinate
  • Urinating more often than usual
  • Fever and chills if an infection is present
  • Nausea and vomiting

What causes kidney stones?

There are several factors that can increase the risk of developing kidney stones:

  • Dehydration – Not drinking enough water each day raises the concentration of minerals in urine
  • Diet – Eating a lot of sodium, protein, and sugar promotes stone formation
  • Obesity – Linked to uric acid stones and other types of stones
  • Digestive disorders – Conditions like Crohn’s disease and ulcerative colitis increase risk
  • Other medical conditions – Diabetes, hypertension, hyperparathyroidism, gout, etc.
  • Medications – Certain diuretics, calcium-based antacids, and tetracycline antibiotics
  • Family history – Having a family member with kidney stones increases your risk
  • Previous kidney stones – After having one, there is a 50% chance of having another within 5 years

How are kidney stones diagnosed?

Kidney stones are often diagnosed through a combination of:

  • Medical history – Discussing your symptoms and risk factors
  • Physical exam – Checking for signs of pain and discomfort
  • Imaging tests – CT scan, ultrasound, X-rays to look for stones
  • Urine test – Looking at chemical composition of urine
  • Blood test – Measuring levels of minerals, kidney function, etc.

Your doctor may ask you to strain your urine to try to capture a kidney stone for analysis. Determining the type of stone can help guide treatment.

How are kidney stones treated?

Treatment options for kidney stones include:

  • Pain relievers – Over-the-counter NSAIDs like ibuprofen or stronger prescription opioids
  • Alpha blockers – Help relax the ureter to facilitate stone passage
  • Calcium channel blockers – Relax ureter muscles and ease pain
  • Surgery – For very large stones that won’t pass naturally
  • Sound wave therapy – Breaks up stones into smaller fragments

For smaller stones, simply drinking plenty of water to flush it out may be effective. Larger stones often require more intensive treatments.

How can you prevent kidney stones?

To lower your risk of developing kidney stones:

  • Drink plenty of fluids, especially water
  • Limit sodium intake to 1500-2300 mg per day
  • Eat less animal protein like meat, poultry and fish
  • Get enough calcium from foods rather than supplements
  • Reduce oxalate intake from foods like spinach and rhubarb
  • Limit sugar, chocolate, cola drinks, and nuts

Medications that reduce the amount of stone-forming minerals in your urine may also be prescribed by your doctor.

Can cranberry juice help treat or prevent kidney stones?

There has been some research into whether cranberry juice can help prevent and treat kidney stones. Cranberries contain quinic acid, malic acid, citric acid and other phytochemicals that may provide some benefits by:

  • Increasing urine flow and diluting stone-forming minerals
  • Binding to stone crystals and blocking further growth
  • Altering urine pH to help dissolve certain stone types
  • Preventing calcium oxalate stone formation

However, the evidence on cranberry juice for kidney stones is mixed. Here is a summary of key research findings:

Studies showing potential benefits of cranberry juice

  • A 2016 study in rats found that cranberry juice increased urine output and prevented kidney stone formation.
  • A 2015 study showed cranberry juice changed urine composition and raised urine pH, which may help reduce kidney stone recurrence.
  • An older 1993 study found that cranberry juice increased urinary citrate and lowered calcium excretion in both stone formers and normal subjects.
  • A 1984 study revealed cranberry juice increased urinary magnesium and lowered oxalate levels.

Studies showing little or no benefit from cranberry juice

  • A 2022 review concluded that evidence does not conclusively support cranberry juice for kidney stone prevention.
  • A 2021 meta-analysis found that cranberry products did not have a significant impact on urine composition.
  • A 2015 study showed that cranberry capsules increased kidney stone risk factors like oxalate and calcium excretion.
  • A 2012 study found no difference in recurrence rates between people who took cranberry tablets vs. placebo.

Overall, cranberry juice may help increase urine flow and acidity, which could theoretically favor stone passage and discourage stone formation. However, high quality evidence from human clinical trials is still lacking.

What is the recommended dosage of cranberry juice?

There is no standard recommended dosage of cranberry juice for kidney stones. Some studies have used 24-32 ounces (700-950 mL) per day divided into 2-3 doses. Fruit juices can add a lot of sugar to your diet, so drinking cranberry juice in moderation is advised.

Instead of juice, cranberry extract pills or powders are another option that avoid the extra sugar. 300-500 mg per day of cranberry extract has been used in studies. Consult your doctor for advice on the appropriate dosage for your situation.

How long until you see results from drinking cranberry juice?

It may take several weeks or months of regular cranberry juice consumption to know if it will help prevent kidney stones from forming or recurring. Cranberry juice is thought to help facilitate stone passage, but effects likely depend on stone size and location. Larger stones may require other medical treatments.

Monitor your symptoms carefully as you try cranberry juice. Keep notes on the frequency and severity of stone attacks and any changes you notice in pain levels. Urine straining can reveal if you are passing more stone fragments after starting cranberry juice. Discuss your progress with your healthcare provider.

Are there risks or side effects from drinking cranberry juice?

Cranberry juice is likely safe when consumed in normal food amounts. However, there are some potential side effects to know about if drinking large amounts of cranberry juice or taking cranberry extract supplements:

  • May cause mild stomach upset, diarrhea, or nausea
  • Contains high amount of natural sugar – may be unsuitable for diabetics
  • Can interact with blood thinning medications like warfarin
  • May increase risk of kidney stones in those prone to oxalate stones
  • Cranberry extract pills may cause headache, rash, dizziness, and liver toxicity

Cranberry juice and extract may also interact with antibiotics, alcohol, anti-inflammatories, diuretics, and other medications. Those on a kidney stone medical regimen or strict diet should exercise caution.

Who should avoid or limit cranberry juice?

Certain individuals should use caution or avoid drinking too much cranberry juice:

  • Pregnant and breastfeeding women
  • People with diabetes – due to the sugar content
  • Those taking blood thinning medications like warfarin
  • People with a history of calcium oxalate stones
  • Those with a cranberry allergy or sensitivity
  • People following a low oxalate diet
  • Individuals taking antibiotics or anticoagulants
  • People with underlying liver disease or kidney disorders

Speak with your healthcare provider before regularly consuming cranberry products if you have any medical conditions or take prescribed medications.

What is the bottom line on cranberry juice for kidney stones?

Current evidence on cranberry juice for kidney stones is somewhat contradictory. Preliminary research in rats and some small human studies suggest cranberry juice could help increase urine flow, decrease stone formation risk factors, and facilitate stone passage. However, larger controlled trials are needed to truly determine efficacy and optimal dosing strategies.

Cranberry juice is fairly safe when consumed in moderation. It may provide additional hydration and minor stone prevention benefits. But it is likely most effective when combined with standard medications, diet changes, and increased water intake. Speak to your urologist or nephrologist before relying solely on cranberry juice as a kidney stone treatment.