Dietary factors play a crucial role in kidney stone formation. Discover how calcium-oxalate binding can help prevent the most common type of stones.
Why Some People Develop Kidney Stones
Kidney stones can be a painful condition. Among the various types of kidney stones, calcium oxalate stones are the most common. Other types are struvite stones, uric acid stones, and cystine stones. [1]
Prior articles listed high- and low-oxalate foods, and provided low-oxalate meal plans. But it is virtually impossible to avoid all oxalates. This article explores the concept of calcium-oxalate binding and provides dietary approaches to help prevent calcium oxalate stone formation.
To effectively prevent their formation, it is important to understand why some individuals are more prone to developing kidney stones. [2-4] Here are some factors that contribute to their development:
Dietary Factors: Diet plays a crucial role in kidney stone formation. Consuming a diet high in oxalate-rich foods, such as spinach, rhubarb, beets, nuts, and chocolate, increases the amount of oxalate in the urine. This can combine with calcium and form stones. Similarly, a diet high in sodium and animal protein can elevate levels of calcium and other substances in the urine. This increases the risk of stone formation. [3]
Dehydration: Inadequate fluid intake can lead to concentrated urine. This promotes the crystallization of substances like calcium and oxalate. These crystals can form kidney stones. Staying properly hydrated helps dilute the urine and reduces the risk of stone formation.
Family History: There can be a genetic predisposition to stone formation. If someone in your immediate family has had kidney stones, you may have an increased risk of developing them as well.
Medical Conditions: Certain medical conditions can increase the likelihood of kidney stone formation. Examples include hypercalciuria (high levels of calcium in the urine), hyperoxaluria (high levels of oxalate in the urine), or urinary tract infections. Other conditions may cause excess calcium or oxalate absorption by the kidneys.
Obesity and Sedentary Lifestyle: Obesity is associated with an increased risk of kidney stones. Additionally, a sedentary lifestyle can contribute to stone formation. Physical activity helps regulate urinary function and prevents the buildup of stone-forming substances.
By understanding these risk factors, individuals prone to kidney stone formation can make informed dietary and lifestyle choices.
Understanding Calcium and Oxalate Interaction
Most people practice oxalate binding without conscious thought. Though not a healthy calorie option, a cheeseburger, french fries (high oxalate), and a milkshake (calcium) are common examples. What’s more difficult is justifying the benefits of binding and learning which foods have high oxalates and which ones contain sufficient calcium.
Even among those with a tendency to form calcium oxalate stones, the body requires at least 1000 mg of calcium daily for proper nutrition. (This is shy of the 1300 mg recommendation from the National Institute of Health for average citizens.) [4]
Under normal circumstances, calcium and oxalate bind together in the intestine and are eliminated from the body. However, if there is insufficient calcium to bind with oxalate, the body may reabsorb the oxalate. It then passes into the urine, increasing the risk of calcium oxalate stones. Hence, consuming adequate dietary calcium is essential for individuals prone to calcium oxalate stone formation.
Food Combinations to Promote Calcium-Oxalate Binding
A method called calcium-oxalate binding can minimize the risk of calcium oxalate stone formation. This approach aims to ensure adequate calcium intake while reducing the prevalence of the most common type of kidney stones.
Pairing calcium-rich foods with oxalate-rich foods may potentially reduce oxalate absorption in the kidneys and mitigate the risk of calcium oxalate kidney stone formation. [5-7] Consider these simple food combinations:
Spinach and Cheese Omelet: Prepare an omelet with spinach. Incorporate a calcium-rich cheese, such as cheddar or Swiss, into the filling.
Calcium-Fortified Tofu Stir-Fry with Arugula: Use calcium-fortified tofu as the protein source in a stir-fry dish. Add arugula as one of the vegetables.
Yogurt and Beet Salad: Combine diced beets (relatively high in oxalates) with a serving of calcium-rich yogurt dressing. Enhance the flavors by adding other salad ingredients like greens, cucumber, and herbs.
Swiss Chard and Feta Stuffed Chicken Breast: Stuff a chicken breast with Swiss chard (contains oxalates). Use feta cheese (which provides calcium) as an additional filling. Bake or grill the chicken for a tasty and nutrient-rich meal.
Almond and Kale Smoothie with Milk: Blend kale (a source of oxalates), almonds (providing healthy fats and protein), and milk or a calcium-fortified plant-based milk alternative.
Broccoli with Parmesan Cheese: Steam or lightly sauté broccoli (moderate oxalate content). Grate some Parmesan cheese over it for added calcium.
Ice Cream with Pistachios: For dessert, combine a scoop of natural vanilla ice cream (which includes calcium, fats, and protein) with pistachios or pecans (a moderate source of oxalates).
Rather than memorizing specific recipes, just focus on the simple concept of pairing dairy (calcium) with moderate-oxalate foods. All nuts have oxalates—some more than others. You need to familiarize yourself with the approximate oxalate levels of various foods. ClinicalPosters has prepared a chart with amounts based on serving size.
Include roasted potatoes with your cheese omelet. Instead of drinking a glass of milk by itself, pour it over cereal with nuts. Add a slice of cheese to a peanut butter sandwich. If you can have sweets, instead of a glazed donut, choose a cookie with nuts to have with a glass of milk.
Tofu is very high in oxalates. On the rare occasion that you prepare a meal with it, purchase a variety that is calcium-fortified. Don’t just eat nuts as an isolated food; pair them with cheese and crackers. That’s the basic concept. Pretty soon, it becomes second nature.
Use balance when binding. Don’t use it as a license to consume all the high-oxalate foods that you strive to avoid. There may be occasions when you have no control over food preparation. In a restaurant or someone else’s home for dinner, oxalate binding can keep you from going hungry.
Suggestions for Restricted Diets
If you’re lactose intolerant, calcium-oxalate binding presents more challenges. There are lactose-free dairy products with calcium and calcium-fortified plant-based beverages like oat milk. Among the most challenging dietary group of diners for kidney stones are vegans, since most of their food sources contain oxalates.
The next challenging dietary group includes vegetarians. However, they do have more options for protein and calcium. Either of these groups might consider a pescatarian diet for the advantages of more protein and essential omega-3.
Exercise Caution With Calcium-Oxalate Binding
There are no recent large-scale clinical trials or double-blind studies on calcium-oxalate binding. While noting some perplexities, Fredric Coe, MD says the premise is based on all three forms of scientific research: empirical science, applied science, and basic science. [7]
You will encounter some questions that require good judgment with this approach. For example, 4 tablespoons of cocoa contains 67 mg of oxalates. That’s high for someone striving to keep below 100 mg daily. Does having the cocoa with milk negate the oxalates? In a more extreme example, a half cup of spinach contains 755 mg of oxalates. Will a slice of cheese in an omelet counteract its effects?
Strive to follow a low-sodium, low-oxalate meal plan. This approach may vary in effectiveness for different individuals. Consult healthcare professionals or registered dietitians to receive personalized recommendations based on your specific needs and medical history.
