Kidney stones are so common that one in ten people will develop one during their lifetime. They occur most frequently between 20 and 40 years of age but can develop at any point during your life. If you’ve had a kidney stone, you know that the pain can be excruciating, but the good news is that you can make some changes to help prevent them. In this article, we share all the basics you need to know about kidney stones.
The Urinary System
The kidneys are an essential part of the urinary system in your body. Here are the basic functions of your urinary system:
- Kidneys: filter wastes and extra water from the bloodstream
- Ureters: carry urine from the kidneys to the bladder
- Bladder: stores urine
- Urethra: the path by which urine exits the bladder
The kidneys perform many functions, including:
- Maintaining stable levels of electrolytes
- Creating hormones that keep blood pressure stable
- Making red blood cells and helping to keep bones strong
Your kidneys work day and night to filter 120 to 150 quarts of blood to produce about 1 to 2 quarts of urine each day.
Your urine typically contains certain substances such as calcium, oxalate, and phosphorus. These are naturally excreted by your kidneys, but sometimes they can become too concentrated in the urine. When the amount of these substances is too high in your urine, they begin to form crystals resulting in the formation of kidney stones.
On the other hand, magnesium and citrate, two other substances found in the urine, discourage these crystals from sticking together. They are called stone inhibitors. When the concentration of crystals is too high and the inhibitors are too low, a kidney stone will form.
Types of Kidney Stones
Most kidney stones contain calcium, with the calcium being bound to either oxalate or phosphate. Calcium oxalate (alone or in combination) is the most common type of kidney stone. Calcium phosphate stones are relatively uncommon.
Roughly 15% of kidney stones contain no calcium at all. These include uric acid stones, struvite stones, and cystine stones. In this article, we will focus our discussion on calcium oxalate kidney stones only.
Calcium Oxalate Kidney Stones
These hard, pebble-like stones may be as small as a grain of sand, and in very rare instances, as big as a golf ball. They may be smooth or jagged and are often yellow or brown in color.
A stone first forms in the kidney, and if it’s small enough, it may travel through the urinary system and be excreted in urine, which may not cause much pain. However, when a kidney stone is too large to move through the urinary system, this creates a back-up of urine in the kidney, ureter, bladder, or urethra. Depending on where the stone lodges, and this causes pain.
Lab Tests and Analyzing Kidney Stones
When possible, it is beneficial to send your stone or a piece of your stone to the lab for analysis to determine the type of kidney stone. If you have had a stone removed, your doctor will send it in for analysis. If you pass a stone at home, you may be able to capture it by using a strainer during urination.
Your doctor may recommend specific lab tests to measure the amount of chemicals in your blood and urine. These tests can help determine possible causes of your kidney stones, and these results can guide your prevention plan.
Prevention of Kidney Stones
By choosing your foods carefully, drinking enough fluids, and adding specific nutrients to your diet, you can help prevent kidney stones.
Avoid high protein diets.
In a study in the New England Journal of Medicine, men who ate a diet low in protein and sodium (salt), along with healthy calcium-rich foods, were less likely to develop calcium oxalate stones than men who ate a low-calcium diet.
People who follow fad diets to lose weight quickly often eat large amounts of protein. This can be a problem since too much protein makes urine more acidic, promoting kidney stone formation. It is important to stick to a balanced diet and avoid fads that include too much animal protein such as beef, chicken, pork, cheese, milk, eggs, and fish.
Limit foods rich in oxalates.
Your urologist may recommend that you follow a low oxalate diet. The amount of oxalate in the diet affects the amount of oxalate in the urine, and too much oxalate can promote kidney stone formation. Foods highest in oxalate are:
Foods highest in oxalate are:
- Chocolate or cocoa
- Wheat germ
- Black teas (not green or herbal)
- Tree nuts (almonds, cashew, and hazelnuts are highest in oxalate),
- Legumes (beans, peanuts, and soybeans).
Generally, when you avoid these foods, the oxalate content of other foods in your diet will total about 40-50 mg per day, which is the amount recommended for people who need to limit dietary oxalate levels.
When you consume drinks or foods rich in oxalates, one way to help your body manage this is to consume calcium-rich foods. An example would be having a glass of calcium-rich milk with black tea, which is high in oxalates.
Eat calcium-rich foods.
Dr. Michael Jenkins of Advanced Urology Institute recommends increasing your calcium intake from food to prevent kidney stones. Including milk and dairy products in your diet can help protect against calcium oxalate stone formation. The calcium found in these foods can bind to dietary oxalate found in the gut, reducing oxalate levels in the urine. Your diet should include 1,000 to 1,200 mg of calcium daily from foods.
It’s best to get your calcium from food; however, if you have been told to take calcium supplements for bone health, choose a supplement that contains calcium citrate since citrate helps inhibit stone formation.
Avoid high-dose vitamin C supplements.
High dose vitamin C supplements may increase your risk of kidney stones since this can increase urinary oxalate levels. Avoid taking vitamin C supplements in large amounts such as 500 mg or higher.
Choose a low-sodium diet.
Higher sodium intakes lead to increased calcium in the urine and reducing sodium intake decreases urinary calcium levels. By cooking at home more often, choosing less processed and fast foods, reading nutrition facts labels, and switching to pepper, herbs, and spices instead of adding salt to foods, you can control the amount of sodium you eat.
Drink plenty of fluids.
It is important to drink enough fluids to help decrease the risk of stone recurrence. Water is best, but it is not your only option. Here are your total fluid intake goals, which include water, milk, juice, tea, coffee, and anything else you drink in a day.
In one large study, sugar-sweetened soda was linked to the development of kidney stones. Limit your intake of soda and other high-sugar beverages. The National Academy of Medicine recommends a fluid intake of approximately 9 cups a day for women and 12 cups a day for men.
- Heat and physical activity boost your fluid needs, even if you don’t sweat.
- Experts recommend drinking enough to produce at least 2 liters (68 ounces) of urine per day.
Lemon juice has been found to increase the level of citrate in the urine, and drinking lemonade, made with real lemons, can increase your fluid intake. You can squeeze lemons into your water or try a recipe using less sugar and lemon zest. If you’re using a sweetener, be sure to limit stevia, which is high in oxalates.
Increase your intake of stone inhibitors such as magnesium, potassium, and citrate, and increase your vitamin B6 intake to decrease oxalate production.
Magnesium, potassium, and citrate can reduce calcium-based kidney stones from forming by increasing kidney stone inhibitors in the urine. Rich sources of magnesium include legumes, nuts, seeds, and whole grains. Potassium is also found in various foods, including fruits and vegetables (potatoes), soybeans, and potatoes. Meats, poultry, fish, milk, yogurt, and nuts also contain potassium.
Vitamin B6 can decrease oxalate production, and this, in turn, may reduce the risk of calcium oxalate stone formation.
Your kidneys and urinary system work hard to keep you healthy. A few changes in diet, fluid intake and nutrients can help prevent kidney stones and help your urinary system run smoothly.
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