A kidney stone is a hard mass with sharp corners that forms from substances in the urine, one of which is typically calcium. A stone may be as tiny as a grain of sand or as large as or even larger than a pearl. Kidney stones form when the components of urine – water and various minerals and acids – are out of balance. When this occurs, the urine may contain more crystal-forming substances than the available fluid can dilute.
Some kidney stones do pass out of the body with the urine, but when a stone does not pass on its own, it can be broken apart by shock waves (ESWL) or other medical intervention may be required.
One person in 10 is likely to develop a kidney stone; the most likely candidate is a white (Caucasian) male over 40 years of age, for whom there is a 50 percent chance of recurrence. Because kidney stones run in families, genetics may have something to do with it, however, eating patterns also run in families and, fortunately, we do have control over our dietary choices.
Those who have had stones (and managed to catch them on the way out) can find out the type of crystals that were in the stone through laboratory analysis. Of the possibilities, the majority are calcium oxalate stones. The next most common variety are calcium phosphate stones.
Preventing kidney stones:
1. Make it a habit to drink lots of water. Have water with meals. Carry a water bottle. Substitute water for coffee, alcoholic beverages and pop. Fruit juice, lemonade and vegetable juices such as carrot juice are also helpful. (Tomato juice is beneficial too although most brands contain high levels of salt.) Don’t allow yourself to become dehydrated during a long hike or throughout a prolonged period of exercise and/or when you’re sweating profusely. Water helps to flush away the substances that form stones in the kidneys. To prevent the recurrence of stones, drinking 3 to 4 litres or quarts of water a day is recommended.
2. Recent research indicates that, for many people, a shift in the direction toward a more alkaline diet can be a key to prevention. This means eating more fruits and vegetables, which tip the pH of the urine in an alkaline direction and also provide potassium, and less animal protein (meat, fish, poultry and cheese, especially processed cheese), which tip the pH of the urine in an acidic direction.
3. Once the type of kidney stone has been identified, one’s doctor or registered dietitian can provide information on preventing the recurrence of stones. Specific dietary recommendations depend on the makeup of the stone. This may involve reducing one’s intake of salt, sodium, high oxalate foods (such as rhubarb, Swiss chard, spinach, beet greens, chocolate and berries) and sweetened pop. And while it can be important to consume enough calcium, avoid excessive amounts.
4. Excess body weight is linked with the risk of developing kidney stones. An explanation for this may be that those who are overweight or obese tend to have more acidic urine and also may consume greater quantities of the foods linked with acidic urine. Weight reduction and achieving one’s optimal body weight can be helpful. It is also valuable to take health measures to reduce hypertension.
3. Li WM et al. Association of body mass index and urine pH in patients with urolithiasis. Urology Research. May 26 2009
Vesanto Melina is a registered dietitian and author of a number of nutrition classics, including Becoming Vegetarian, Becoming Vegan, Raising Vegetarian Children and the Food Allergy Survival Guide. To book a personal consultation with Vesanto in Langley, call 604-882-6782 .www.nutrispeak.com
Symptoms of kidney stones include:
- extreme pain in one’s back or side (in the kidney area).
- blood in the urine (the crystal can scratch the lining of tubules in the kidney area).
- a burning feeling when urinating.
- fever, chills and vomiting.
Fortunately, the damage is not permanent, although that is of little consolation during the experience.