Kidney stones and how to avoid them

Kidney stone pain is often compared to labour pain, and trying to pass a stone is excruciating! For those prone to kidney stones, preventing them is a must—follow these tips to avoid developing kidney stones.

• One in every 1,000 Canadians is hospitalized each year because of kidney stones (or renal calculi), which occur when stone-forming compounds from the urine accumulate in the kidney and start to crystallize.
• The stones are typically composed of calcium, combined with phosphate or oxalate. Less common are so-called struvite stones, which can result from kidney or chronic urinary tract infection; and even less frequently, gout-related uric acid stones may form.
• Passing one kidney stone dramatically increases the chance of having another stone, but experts believe these odds can be improved through exercise and diet alterations.

• Heredity and chronic dehydration seem to contribute to kidney stone formation, but the specific cause is unknown.
• Certain factors and conditions may predispose individuals to kidney stones, including a sedentary lifestyle and being Caucasian or Asian.
• Some people tend to have higher concentrations of calcium in their urine, which promotes crystal formation and accounts for the majority of stones.
• Additional risk factors include kidney disease, chronic bowel inflammation, intestinal surgery and medications such as diuretics.
• For those who are susceptible, oxalates and purines may fuel stone formation.

Water: Drinking plenty of fluids, especially water, is perhaps the most important dietary advice for the prevention and management of kidney stones. Water dilutes the urine, making it difficult for salts to crystallize and stones to form. Note that diluted urine should not be darker than pale yellow, and fluid intake should be adjusted accordingly. Experts recommend drinking three litres (12 cups) of water a day to avoid kidney stones.

Citrus juice: Research suggests that drinking orange juice and lemonade may effectively help prevent kidney stones. In addition to the beneficial water content of lemonade and orange juice, alkaline substances called citrates in these juices may help neutralize stone-forming acids, inhibiting the formation of certain calcium-based kidney stones. Incidentally, the valuable mineral potassium, also found in orange juice and lemonade, may be useful since potassium is linked to a reduced risk for kidney stones.

Blueberries: To help prevent struvite kidney stones, eat tannin-rich blueberries. Although cranberries have tannins, they should be avoided because they are high in oxalates.

Plant protein: People prone to developing kidney stones may benefit from eating more plant protein and less animal protein, which may elevate the concentration of stone-forming calcium and oxalates in the urine. Because urinary calcium and oxalates contribute to kidney stones, foods high in insoluble fibre (but low in oxalates) may help by binding excess oxalates and calcium in the digestive tract, preventing their accumulation in the urine.

Magnesium: Magnesium may be beneficial as well, because it may bind oxalates in the intestines. It's important to check with your doctor before substantially increasing fibre consumption, because reducing calcium levels may raise the risk for bone-thinning osteoporosis.

Calcium: Two powerful observational studies found that people who ate the most calcium-rich foods were significantly less likely to suffer from calcium-based kidney stones. Researchers surmise that dietary calcium may block the body's absorption of harmful oxalates. Study subjects who consumed the most dietary calcium also consumed the most fluids, potassium, magnesium and phosphate. However, calcium consumed in supplement form may actually increase the risk for stones.

People at risk for kidney stones should limit or avoid refined carbohydrates, salty foods, alcohol, foods high in animal protein, purine-rich foods and oxalate-rich foods.

Purine-rich foods include: organ meats, anchovies, sardines and herring.

Foods high in oxalates include: beets and beet greens, chocolate, chard, cranberries, dandelion greens, nuts, parsley, rhubarb, spinach, strawberries, tea and wheat bran.

• Broccoli
• Peas
• Avocados
• Quinoa
• Bananas
• Potatoes
• Blueberries