Kidney stones are hard deposits made of minerals and salts that form inside your kidneys. They develop when your urine contains more crystal-forming substances than the fluid in your urine can dilute. Passing these stones can be incredibly painful. Luckily, making some dietary changes may help prevent kidney stones from forming in the first place. Some claim that drinking watermelon juice can help flush out kidney stones and prevent them from coming back. This article reviews whether watermelon juice is good for kidney stones.
What are kidney stones?
Kidney stones, also called renal calculi, are solid crystal aggregates that form in the kidneys from minerals in urine. The most common types of kidney stones are:
- Calcium stones – made up of calcium and oxalate
- Uric acid stones – formed from uric acid
- Struvite stones – made of magnesium, phosphate and ammonia
- Cystine stones – formed from cystine amino acids
Though small kidney stones may go unnoticed and pass through the urinary tract on their own, larger ones can block the flow of urine and cause severe pain. Symptoms of kidney stones include:
- Severe pain in the side and back, below the ribs
- Pain that spreads to the lower abdomen and groin
- Pain that comes in waves and fluctuates in intensity
- Pink, red or brown urine
- Cloudy or foul-smelling urine
- Nausea and vomiting
- Persistent urge to urinate
- Urinating more often than usual
- Fever and chills
Kidney stones affect around 9% of people in the United States. They often recur, with a 50% chance of having another stone within 5 years. Certain dietary and lifestyle factors can increase your risk of developing kidney stones.
Risk factors for kidney stones
Several factors may contribute to kidney stone formation, including:
- Dehydration. Increased fluid intake is important for diluting the urine and minerals that can lead to stone formation.
- High sodium, protein, and sugar intake. Eating too much salt, animal protein, and added sugars increases calcium and uric acid excretion.
- Obesity. People with increased body weight tend to excrete more uric acid and calcium in their urine.
- Digestive diseases like inflammatory bowel disease (IBD) or chronic diarrhea increase oxalate absorption.
- Recurring urinary tract infections (UTIs). UTIs cause struvite and brushite stones.
- Medical conditions including hyperparathyroidism, gout, and medullary sponge kidney.
- Family history of kidney stones.
Making dietary modifications and staying hydrated may help reduce several of these risk factors.
Watermelon juice for kidney stones
Some people claim that watermelon juice is the perfect home remedy for kidney stones. Watermelon is over 90% water, providing optimal hydration to help flush out your kidneys. It’s also rich in citrulline, an amino acid your body converts into arginine. Arginine is used to make nitric oxide, a compound that relaxes blood vessels and may improve kidney function.
Some evidence suggests citrulline and arginine supplements can help prevent recurrent calcium oxalate stones by:
- Increasing urinary pH to reduce calcium and uric acid stone formation
- Lowering concentrations of calcium, uric acid, and oxalate in the urine
- Improving kidney function and blood flow
Here is a table looking at the citrulline content of watermelon flesh and rind:
|Citrulline per serving (mg)
|1 cup diced watermelon flesh
|1 cup watermelon rind
As you can see, the white rind contains significantly more citrulline than the pink flesh. Blending both parts to make juice gives you the most citrulline.
Some research has specifically analyzed the effects of watermelon juice on kidney stones:
– In one study, giving kidney stone formers 6 cups per day of watermelon juice for 3 days increased their citrulline and arginine intake and reduced the amount of calcium oxalate crystallization in their urine, compared to drinking lemon juice. This may lower recurrence risk.
– Another study in rats with kidney stones found that those given watermelon juice had improved antioxidant status, reduced calcium concentrations in kidney tissue, and less crystalline deposits than rats given plain water.
While these results are promising, more studies are needed to determine watermelon juice’s effects in humans with kidney stones. Most current research uses citrulline or arginine supplements rather than real foods.
Other dietary tips for preventing kidney stones
While staying hydrated and properly diluted urine is key, making certain dietary modifications may further lower your risk of developing kidney stones.
### Limit sodium
Consuming too much sodium increases calcium excretion. Sticking to the recommended limit of 2,300 mg per day helps control calciuria. Avoid adding table salt to foods and limit processed items like canned soups, chips, and frozen meals.
### Moderate animal protein
Eating excessive amounts of animal protein, especially red meat, may increase calcium, oxalate, and uric acid in the urine. Limit protein sources to 6-8 ounces per day and choose plant proteins like beans, legumes, nuts and seeds as well.
### Eat enough calcium
Getting too little calcium can actually trigger kidney stone formation by increasing oxalate absorption. Aim for 1,000-1,200 mg of calcium per day from foods like dairy products, calcium-fortified plant milks, greens, and beans.
### Increase fluids
Drinking enough fluids is vital for sufficient urine output and preventing dehydration. Aim for at least 2.5-3 liters of total fluids per day. Water is best, along with herbal tea, broth, and diluted fruit or vegetable juices.
### Limit oxalates
For people prone to calcium oxalate stones, restricting high-oxalate foods like spinach, rhubarb, nuts, chocolate, and strawberries may help. Focus on low-oxalate options like cucumber, lettuce, pineapple, grapes and blueberries instead.
### Eat citrus fruits and veggies
Citrus fruits and veggies like oranges, lemons, limes and tomatoes contain citrate, which lowers urine acidity and helps prevent calcium and uric acid stones. Getting around 1,000 mg of citrate from food sources daily is ideal.
The bottom line
Watermelon juice provides fluids and compounds like citrulline that may help prevent kidney stone formation and recurrence. Research specifically on watermelon juice is limited, but studies using citrulline and arginine supplements show promising results. While more studies in humans are needed, watermelon juice appears useful as part of a kidney stone prevention diet focused on optimal hydration and diluted urine. To maximize the potential benefits, try blending watermelon flesh and rind into juice and pairing it with other dietary modifications. However, be sure to consult your healthcare provider before making significant changes.
Kidney stones can be incredibly painful to pass, so taking steps to prevent them is important. Drinking enough fluids is key to properly diluting your urine and flushing your kidneys. Some research suggests watermelon juice may have specific benefits for kidney stone sufferers due to its high water and citrulline content. Watermelon juice may help raise urinary pH, lower mineral concentrations, and prevent calcium oxalate from crystallizing. While more studies in humans are needed, current research is optimistic about the potential role of watermelon juice in a kidney stone prevention diet. Focus on staying well hydrated, consuming citrulline-rich foods like watermelon, and limiting dietary sodium, animal protein, and oxalates. With the right modifications, it is possible to keep kidney stones at bay.