Foods that contain oxalates and that should be avoided include:beetroot, asparagus, rhubarb, chocolate, berries, leeks, parsley, celery, almonds, peanuts and cashew nuts, soy products, grains, such as oatmeal, wheat germ and wholewheat, teas, colas.
Still, you should not reduce your calcium intake unless your doctor advises you to do so. Here are practical and easy dietary adjusments that you can follow to reduce the risk of kidney stone formation:
1- Plenty of water: you're already doing that, let's make sure you're doing it correctly. The extra water dilutes the substances in urine that lead to stone formation. Aim at drinking enough fluids to pass 2 liters of urine a day. It doesn't always have to be pure water, you may include some citrus beverages, like lemonade and orange juice (but watch out for too much sugar!) The citrate in these beverages helps block stone formation.
2- Calcium: A diet poor in calcium can cause oxalate levels to rise and cause kidney stones. To prevent this, a diet that contains the right amount of calcium for your age is required.It is best that you obtain calcium from foods, since some studies have linked taking calcium supplements to kidney stones.
3- Reduce sodium: A high-sodium diet can trigger kidney stone formation by increasing the amount of calcium in the urine. The latest guidelines recommend limiting total daily sodium intake to 2,300 mg. If sodium has contributed to kidney stones in the past, try to reduce your daily intake to 1,500 mg. This beneficial for for your blood pressure and heart.
4- Limit animal protein: Eating too much animal protein, including red meat, poultry, eggs, and seafood, raises the level of uric acid and could lead to kidney stones. A high-protein diet also depletes citrate, the chemical in urine that helps prevent stones from forming. If you’re prone to stones, limit your daily meat intake to a quantity that is no bigger than a pack of playing cards. This is also healthy for the heart, and a good cancer-preventive measure.
5- Avoid dehydration: Saunas and heavy exercise are healthy practices, but they also may lead to kidney stones, because losing water through sweating - whether due to these activities or just hot weather- leads to less urine production. The more you sweat, the less you urinate, which allows for stone-causing minerals to settle and bond in the kidneys and urinary tract. So always keep well hydrated, especially when engaging in exercise or activities that cause a lot of sweating.