When minerals collect in the kidneys and crystallize, stones develop. This is more likely to occur if the urine is highly concentrated, since it contains more substances capable of crystallizing. Drinking too little fluid forces the kidneys to work harder and leads to more concentrated urine. Drinking plenty of fluids is an important course of action to prevent kidney stones. A diet high in animal protein can also increase urine concentration.
Studies show that vegetarians are less likely to suffer from kidney stones.
Although there is a connection between calcium and kidney stones, eating high- calcium foods does not always cause stones. There are even times when calcium helps prevent them. What makes the difference between a calcium-friendly food and one that is not is how well the body absorbs the calcium. If calcium absorption from the diet is adequate then the body does not need to dissolve calcium in the bone, which then raises the calcium level in the blood. When this blood gets filtered through the kidneys, calcium deposits form.