For individuals managing kidney stones or chronic kidney disease (CKD), dietary adjustments often include limiting animal protein, sodium, and oxalate intake, while ensuring adequate consumption of fruits, vegetables, and a moderate amount of calcium. Plant-based diets have become increasingly popular due to concerns about health, the environment, and animal welfare. As plant-based dairy substitutes become more widely consumed, it is crucial for both healthcare providers and patients with renal conditions to understand their nutritional composition, especially concerning factors that influence kidney stone formation and CKD management.
Understanding Oxalate and Kidney Stones
Calcium oxalate stones are the most prevalent type of kidney stone, accounting for approximately 80% of cases in the United States. Oxalate, or oxalic acid, is a compound produced by the body and found naturally in various foods, including fruits, vegetables, nuts, and grains. While small amounts of oxalate and calcium in the urinary tract typically pose no issues, they can bind together to form kidney stones in certain instances, particularly when urine volume is low and oxalate excretion is high.
The Low Oxalate Diet
A low oxalate diet aims to reduce the amount of oxalate excreted through urine. Though recommendations can vary, most healthcare providers advise limiting oxalate intake to less than 40-50 mg per day. This involves primarily consuming foods like proteins, dairy products, white rice, and low oxalate fruits and vegetables. Soaking and cooking certain vegetables and legumes can further reduce their oxalate content.
Foods to Include
Many foods are naturally low in oxalates and can be enjoyed as part of a low oxalate diet:
- Fruits: Bananas, blackberries, blueberries, cherries, strawberries, apples, apricots, lemons, peaches
- Vegetables: Mustard greens, broccoli, cabbage, cauliflower, mushrooms, onions, peas, zucchini
- Grains and Starches: White rice, corn flour, oat bran
- Proteins: Eggs, meat, fish, poultry
- Dairy Products: Yogurt, cheese, milk, butter
- Beverages: Coffee, water, fruit juice (e.g., Simply Orange Juice Light for calcium fortification)
- Herbs and Spices: Cinnamon, cilantro, cumin, dill
Foods to Avoid
A low oxalate diet limits foods high in oxalates:
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- Fruits: Rhubarb, kiwis, dates, raspberries, oranges, tangerines
- Vegetables: Spinach, chard, potatoes, beets, turnips, yams, okra, carrots
- Legumes: Navy beans, fava beans, kidney beans, refried beans
- Nuts: Almonds, walnuts, macadamia nuts, cashews
- Seeds: Sunflower seeds, pumpkin seeds
- Chocolate and Cocoa
- Grains and Starches: Brown rice, couscous, millet, bulgur, cornmeal, corn grits
- Beverages: Chocolate milk, hot chocolate, tea, tomato juice
- Soy Products: Tofu, soybeans, soy burgers
Dairy vs. Plant-Based Milk Alternatives
Traditional recommendations often include dairy as a good source of calcium for kidney stone prevention. However, not everyone can tolerate dairy due to lactose intolerance, animal welfare concerns, or other dietary preferences. This has led to the increasing popularity of plant-based milk alternatives.
Nutritional Comparison
A recent study published in the Journal of Renal Nutrition evaluated the concentrations of ingredients that either promote (sodium, oxalate) or inhibit (calcium, potassium) stone formation in various milk alternatives. Sodium, calcium, and potassium content were obtained from nutrition labels, and oxalate levels were meticulously measured.
- Calcium: Macadamia milk has the highest calcium content, followed by soy, almond, rice, and dairy milk. Cashew, hazelnut, and coconut milk have the lowest calcium levels.
- Oxalate: Almond milk has the highest oxalate concentration, followed by cashew, hazelnut, and soy. Coconut and flax milk have undetectable oxalate levels.
- Sodium, Potassium, and Other Minerals: Coconut milk is low in sodium, calcium, and potassium, while flax milk has the most sodium. Oat milk has parameters most similar to dairy milk, with moderate calcium, potassium, and sodium, and low oxalate.
Plant-Based Milk Alternatives for Kidney Stone Formers
- Favorable Options: Oat, macadamia, rice, and soy milk compare favorably with dairy milk in terms of kidney stone risk factors, offering moderate calcium and potassium, modest sodium, and low oxalate levels.
- Less Favorable Options: Almond and cashew milk have more potential stone risk factors due to their higher oxalate content.
Plant-Based Milk Alternatives for Chronic Kidney Disease (CKD)
- Favorable Options: Coconut milk is a favorable dairy substitute for patients with CKD due to its low potassium, sodium, and oxalate content. Macadamia milk may also be an option, though it has a higher sodium content than coconut milk.
Specific Milk Alternatives: A Closer Look
Coconut Milk
Coconut milk is a versatile and flavorful option that is naturally low in oxalate. In fact, researchers found that coconut milk had such little oxalate that it couldn’t be picked up by the analyzer, effectively making it a 0 mg oxalate option. However, it's important to note that coconut milk tends to have more fat compared to low-fat or skim milk.
Almond Milk
Almond milk tends to be the most popular plant-based milk, but it is very high in oxalate. One cup (8 fluid ounces) of almond milk has 27mg of oxalate, the most oxalate of any plant-based milk.
Flax Milk
Flax milk has 0mg of oxalate.
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Oat Milk
Oat milk is another low oxalate option, at only 4mg oxalate per cup. Oat milk is known for being an especially creamy plant-based milk option. It also tends to be higher in calcium than other plant-based milks.
Additional Considerations for Managing Kidney Stones
While a low oxalate diet and choosing appropriate dairy alternatives are important, other dietary modifications can also help reduce the risk of calcium oxalate kidney stones:
- Increase Calcium Intake: Aim for 1,000-1,200 mg of calcium per day from foods like dairy products, leafy greens, sardines, and seeds. Calcium binds with oxalate in the digestive system, reducing its absorption and preventing kidney stone formation.
- Limit Salt Intake: High salt consumption may increase the risk of kidney stones.
- Avoid Vitamin C Supplements: The body converts vitamin C into oxalate, so avoid high-dose supplements unless recommended by a healthcare provider.
- Stay Hydrated: Adequate fluid intake increases urine output and reduces the risk of kidney stone formation.
- Magnesium, Chloride, Phosphorus and Sulfate Content: In addition, data were not available for the magnesium, chloride, phosphorus and sulfate content for all of the products examined in this study, and some products only list the %RDA for calcium, not the exact content.
Addressing Common Misconceptions
It's important to dispel some common misconceptions about oxalate and its impact on health:
- Oxalate and Autism: Despite some claims, there is no research suggesting that dietary oxalates cause autism or that a low oxalate diet benefits autism treatment.
- Oxalate and Vulvodynia: While some individuals with vulvodynia may find pain management easier with a low oxalate diet, studies have not established a direct link between dietary oxalate consumption and the development of vulvodynia.
Potential Drawbacks of Low Oxalate Diets
Low oxalate diets can be restrictive, limiting many healthy and nutritious foods. For example, spinach and beets are high in oxalates but also rich in essential nutrients like fiber, vitamins, and minerals. Vegans and vegetarians may find it challenging to obtain enough protein on a low oxalate diet, as many plant-based protein sources like beans, nuts, and tofu are high in oxalates. Therefore, careful planning is essential to ensure nutritional needs are met.
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