Kidney Nutrition: Oxalates and PKD
If you’ve ever looked up nutrition for PKD you may have seen the word “oxalates”. Is this just another buzz word? Or is it something you should be aware of with PKD? This blog post will cover what oxalates are and why they are important with PKD.
Those with PKD are at increased risk of forming kidney stones. In fact about 25% of people with PKD develop kidney stones. Treatment for PKD focuses on slowing the progression of kidney disease and also treating associated conditions of PKD like kidney stones. The risk with kidney stones is that they can cause pain or block the flow of urine which impacts the kidney function. As a result, nutrition strategies should also target decreasing risk of forming kidney stones.
What Are Kidney Stones?
Kidney stones (also called nephrolithiasis) affect 1 in 5 males and 1 in 10 females. Kidney stones form when there is a high level of substances like calcium, oxalate, sodium, cysteine or uric acid are present in the urine. These substances form crystals which leads to stones. The most common type of kidney stone is called a calcium oxalate kidney stone, it is about 80% of all formed stones. Other types of kidney stones include uric acid, struvite, cysteine stones. Kidney stones can also occur if:
- There is low urine volume (typically less than 2.5 L/day)
- Not enough of good nutrients like citrate, magnesium, or potassium
- The pH is too acidic (meaning the pH is less than 6.0)
What Are Oxalates?
Oxalates are a non-nutritive compound found in many foods. They are called non-nutrient because they don’t provide our bodies with something we need; compared to things like potassium or magnesium. When we do consume oxalates we excrete them in the urine, and too much oxalate in our urine can be one reason for calcium oxalate kidney stones.
Oxalates are found in plant foods like vegetables, fruit, beans, nuts, seeds, and grains. Some of these foods have more oxalate than others, as explained below. Choosing lower oxalate foods can help to reduce the risk of forming kidney stones with PKD.
Common Oxalate Sources
There are many ways to manage oxalates to prevent kidney stones. Nutrition plays an important role. Working with a registered dietitian who is knowledgeable about PKD and oxalates is important to provide personalized information because while oxalates are readily available in our food, the databases to support how much oxalate in foods are sparse. So, to help here are my top 10 oxalate foods to limit.
- Navy beans
- Wheat berries
Reducing Risk of Kidney Stones with PKD
Reducing your risk of kidney stones with PKD starts with making small nutrition changes. Here are some tips for getting started:
- Understand your risk. Ask your healthcare provider for a 24 hour urine collection which can tell you your urine volume, pH, citrate, calcium, oxalate, magnesium and uric acid levels. Completing this also helps your healthcare team manage your PKD and provide insight into changes to delay cyst formation.
- Drink adequate fluids. The goal is to increase the amount of urine you pass to lower the concentration of stone forming substances like sodium, calcium and oxalate in your urine. Aim to urinate at least 2.5 L per day. Make water your beverage of choice as sugar-sweetened beverages can increase risk of forming stones.
Make diet changes.
- Choose vegetables and fruit more often to obtain potassium, magnesium, citrate and these are alkali producing for the pH. Aim for half your meal to be in vegetables and include fruit at snacks.
- Add lemon juice to your water to add citric acid to your urine.
- Reduce how much and how often you consume high oxalate foods.
- Pair meals with calcium sources to help decrease the absorption of oxalates. Oxalate and calcium attract, so when we eat them together they will bind in the gut and not the kidneys decreasing the risk of forming stones. Choosing calcium from food sources is preferred, not calcium from supplements.
- Eat the right amount and type of protein. Too much animal protein can increase the uric acid load on the kidney and cause kidney stones.
- Limit sodium. Too much salt causes calcium to increase in the urine and changes. Aim for 2300 mg or less sodium per day. Avoid supplements. Some can form kidney stones such as high doses of calcium, vitamin D and vitamin C as these can put you at increased risk of forming kidney stones. Speak with your healthcare team before starting or stopping any supplements.
Being mindful of our diet is one strategy to help with managing PKD. This includes being mindful of how much and how often you consume oxalate foods. Start by becoming aware of these high oxalate foods and looking for lower oxalate options to include more often in your diet. Here are some easy low oxalate swaps:
|High Oxalate||Low Oxalate|
|Almond, Cashew||Pecan, Pistachios|
|Navy Beans||Chickpeas, Lentils|
|Okra, Spinach||Arugula, Broccoli, Cabbage, Kale|
|Rhubarb, Raspberries||Blueberries, Strawberries|
|Wheat berries||Barley, Couscous|
If you are looking for more nutrition support for your PKD. Speak with your healthcare team about seeing a renal dietitian.
Written by: Emily Campbell, RD CDE MScFN is a Registered Dietitian and Certified Diabetes Educator with a Master’s Degree in Foods and Nutrition. Emily specializes in renal nutrition helping those with kidney disease overcome the confusing world of nutrition to promote health. Emily can be found at kidneynutrition.ca