Oxalate Foods And Their Effects on the Human Body

Raspberries, with their delightful taste and antioxidant properties, are a favorite among fruits. However, they also belong to the high-oxalate group, containing about 48 milligrams per cup. While they offer a bounty of health benefits, including vitamins and fiber, those who need to manage their oxalate levels should consider moderating their raspberry intake. Incorporating a variety of lower-oxalate fruits can help maintain a balanced and healthful diet without forgoing these juicy delights.

Soy products, a staple in plant-based diets, are excellent protein sources but come with a high oxalate price. For instance, a 3-ounce serving of firm tofu contains about 235 milligrams of oxalates. Soy milk and yogurt are similarly oxalate-rich. Individuals managing their oxalate intake, especially those with kidney concerns, might need to limit these soy-based favorites or seek lower-oxalate protein alternatives.

Almonds are a nutritional powerhouse, offering a dense concentration of vitamins and minerals. However, they are also significant oxalate contributors, with one ounce (approximately 22 nuts) delivering 122 milligrams of oxalates. For those monitoring oxalate intake, almonds might require careful consideration. Opting for lower-oxalate nuts or moderating almond consumption can be a wise dietary strategy.

The humble potato, a staple in many diets, surprisingly contains a notable amount of oxalates. A medium baked potato, for example, has about 97 milligrams, primarily in the skin. While potatoes are a good source of fiber, vitamin C, and B vitamins, those with oxalate-related health concerns should be mindful of their potato intake, possibly favoring low-oxalate starch alternatives.

Beets are celebrated for their health benefits, including high levels of folate and manganese and their ability to help lower blood pressure. However, they are also among the vegetables highest in oxalates, with 152 milligrams per cup. While their nutritional advantages are undeniable, individuals with a tendency for kidney stones or those on a low-oxalate diet might need to limit beet consumption to maintain a balanced oxalate intake.

Oxalate is derived from plants and, in the body, an end product primarily excreted by the kidneys. Some oxalate is absorbed in the gut, but the amount depends on the diet. Low calcium diets have been linked to increased oxalate absorption, and small bowel reabsorption syndrome and imbalances in the gut biome can also affect oxalate absorption and excretion.

Oxalate and calcium are both naturally present in the urinary tract. For kidney stones to form, an excess of both must be present along with low urine volume. The calcium and oxalate stick together and form crystals and stones. Kidney stones are common, with about 11 percent of men and six percent of women having them at least one in their lifetime. Calcium oxalate stones are the most common type, making up 80 percent of all kidney stones.

People trying to follow a low-oxalate diet should consume less than 100 mg of oxalate a day. Some foods high in oxalate are cooked spinach (755 mg/serving), raw spinach (656 mg/serving), rhubarb (541 mg/serving), rice bran (281 mg/serving), buckwheat groats (133 mg/serving), and almonds (122 mg/serving).

Various cooking methods can significantly reduce the oxalate levels in some foods. Boiling can reduce oxalates in vegetables by as much as 67 percent and some beans by as much as 76 percent. Older research found that boiling was much more effective at lowering oxalate levels in vegetables than steaming; this study found that boiling led to as much as an 87 percent reduction while steaming was only as much as 53 percent.

Getting the right amount of calcium is key to prevent the formation of calcium oxalate stones. Generally, you should get about 1,200 mg of calcium a day, and getting calcium from food rather than supplements is preferred. When you get enough calcium, you lower the amount of oxalate absorbed in the GI tract, thus reducing the risk of stones forming.

Vitamin C intake can increase the risk of oxalate stone formation because vitamin C is partially converted to oxalate and excreted in the urine. Research found that two grams of vitamin C daily increased urinary oxalate excretion by about 22 percent. If you are trying to manage oxalate levels, the recommend daily intake of vitamin C is 40 to 120 mg, depending on gender and age. Talk to your doctor if you have questions about your vitamin C intake.

Oxalate from foods is absorbed in multiple portions of the GI tract, including the stomach and small and large intestines. Generally, the more oxalate you eat, the more your body absorbs. Recent research shows that maintaining a healthy oxalate balance requires a symbiotic community of bacteria in the gut, not a single species. Anything that affects the absorption of food in the gut can alter oxalate levels, including small bowel reabsorption syndrome or imbalances in the gut biome, which can be caused by antibiotics, lack of physical activity, smoking, or stress.

If you are trying to eat a low-oxalate diet, it is important to know what foods to avoid, but knowing what foods are low in oxalate can also be helpful. Kale, romaine lettuce, iceberg lettuce, tomatoes, cauliflower, cucumber, peas, squash, zucchini, yogurt, milk, bread, white rice, corn, oat bran, cottage cheese, eggs, beef, chicken, and fish are all good options.

Oxalates and other natural compounds are sometimes thought to take away from the nutritional value of food. Some of these compounds may bind with certain vitamins, minerals, or nutrients, but but calling them "anti-nutrients" is misleading. Some foods may contain oxalate but be rich in other nutrients that benefit your health. For example, spinach is exceptionally high in oxalate, but it has many nutritional benefits. Spinach is a good source of iron, folic acid, carotenoids, and omega-3 fatty acids and is used in traditional medicine to treat diabetes, asthma, joint pain, and more.

No studies are available that compare the effects of vegan and vegetarian diets on kidney stone formation. Some researchers speculate that a diet high in fruits and vegetables with low animal proteins and a balance of low-fat dairy products or a vegetarian diet can reduce the risk of kidney stones. That said, vegan or vegetarian diets that do not allow for the inclusion of dairy products (and therefore dietary calcium) are likely less protective.

Drinking water can help prevent kidney stones because it dilutes the urine, helping to flush out the substances that lead to stones. Generally, you should try to drink two to three liters of water a day or whatever you need to pass two liters of urine every day. The easiest way to determine if you are drinking enough water is to look at your urine. It should be clear and pale yellow.

If you have a history of calcium oxalate kidney stones, you may benefit from following a low-oxalate diet. You may also want to consider a low-oxalate diet if you have a malabsorption syndrome, bowel disease, or bariatric surgery that affects how your intestines absorb nutrients. Talk to your doctor for advice about how much oxalate you can have in a day, and make sure you get enough calcium from food sources.

Most foods that are high in oxalate are foods that come from plants, whether that is vegetables, grains, legumes, or nuts. Not all food from plants is high in oxalate, and dairy foods and meats like beef, chicken, and fish contain low levels. Eating a balanced diet that includes low-fat animal proteins, fruits, vegetables, and dairy products can keep oxalate levels in check.

If you have calcium oxalate kidney stones, talk to your doctor about whether you need a low oxalate diet. They can guide you on foods you should eat and those you should avoid. If you need help figuring out what to eat or if you are having a difficult time adjusting, talk to a nutritionist who can help you understand what you can and cannot eat and help you put together meal plans to make the changes a little easier to manage.