List of Foods and Drinks That Contain Oxalates
The purpose of this article is to provide a list of foods and drinks that contain oxalates in significant amounts. Getting familiar with this list of oxalate containing foods should help those who are trying to follow a low oxalate diet for health reasons. But before we get to the list, let's take a look at what oxalates are and why they have become such a controversial subject among nutritionists and health experts.
Oxalates and Human Health
Oxalates, also known as oxalic acid, are naturally-occurring substances present in significant amounts in many foods. Oxalates are also found in humans and animals, and our bodies routinely convert other substances into oxalates. Although oxalate-containing foods have been part of the human diet since the dawn of time, it has been suggested that foods rich in oxalates may pose health risks to some people. For example, people with certain medical conditions such as Primary Hyperoxaluria and Enteric Hyperoxaluria are frequently advised to restrict their dietary intake of foods and drinks that are rich in oxalic acid.
Furthermore, those who are susceptible to forming calcium-oxalate kidney stones are often advised to reduce their intake of oxalate-containing foods. However, many experts point out that dietary habits other than oxalic acid avoidance may play a much bigger role in the prevention of kidney stones. In fact, intake of dietary oxalate has been found to account for only 10-15% of the oxalate found in the urine of individuals who form calcium-oxalate stones. Studies suggest that a diet rich in animal protein and salt and an insufficient intake of water may influence the formation of calcium-oxalate stones more than consumption of foods and drinks that contain oxalates.
Foods and Drinks Rich in Oxalates
Note that the oxalic acid content of the selected foods and drinks included in the list below may vary significantly depending on several factors. For example, the quality of the soil in which the plant was grown as well as the age of the plant when it was harvested can have a great impact on the oxalate content of that food. Therefore, all the data on the list should be treated as ballpark estimates only.
Spinach. According to nutrient data provided by the U.S. Department of Agriculture (USDA), a 100-gram portion of spinach provides a whopping 970 milligrams of oxalic acid, and other sources have reported even highest values for this oxalate-rich salad green. People who are trying to restrict their intake of oxalates can substitute kale for spinach in many recipes (especially green smoothies). Contrary to popular belief, kale is not rich in oxalates (see Oxalates in Kale and Spinach).
Rhubarb. The green, inedible leaves of the rhubarb plant are particularly rich in oxalates, but also the edible stalks contain significant amounts. According to data provided by the Department of Nutrition at the Harvard School of Public Health, half a cup of diced rhubarb contains 1082 milligrams of oxalates. This translates into about 887 milligrams per 100 grams of rhubarb.
Purslane. Although purslane is considered a weed in the United States, it is completely edible and packed with health promoting nutrients such as omega-3 fatty acids. On the flip side, purslane is also relatively rich in oxalates. According to a study published in the Journal of Food, Agriculture & Environment in 2007, fresh purslane leaves contain around 230 milligrams of oxalates per 100 grams. The stems and buds, which are also edible, contain significantly less oxalates.
Buckwheat. Buckwheat is a significant dietary source of oxalates, with one cup of cooked buckwheat groats containing 133 milligrams of oxalates, according to the Harvard data. This value corresponds to approximately 79 milligrams per a 100-serving of buckwheat groats.
Amaranth. Amaranth is botanically related to buckwheat, and therefore it is not surprising that also this "pseudo grain" contains large amounts of oxalates. According to USDA data, a 100-gram serving of amaranth provides 1090 milligrams of oxalic acid.
Almonds. Almonds are a concentrated source of oxalates, with one ounce of almonds (about 22 kernels) providing 122 milligrams of oxalates. This corresponds to about 430 milligrams of oxalates per 100 grams of almonds. Also many other nuts and seeds – including cashews, peanuts, pistachios, pumpkin seeds, pecans, walnuts and sunflower seeds – contain significant amounts of oxalates, although the amounts are still moderate (in the range of 35-173 mg per 100 g) compared to the amount of oxalates in almonds.
Cocoa and Dark Chocolate. Cocoa, and consequently dark chocolate, are very rich in oxalates. A 2011 study published in the Journal of Food Composition and Analysis found that the total oxalate content of cocoa powder can range from 650 to 783 milligrams per 100 grams on a dry matter basis (cocoa powder contains very little moisture which implies the values would be very similar on a wet weight basis). In contrast to pure cocoa and dark chocolate, white chocolate is not a significant source of oxalates.
Tea and Coffee. Both tea and coffee contain oxalates, so if you're trying to restrict your intake of this controversial substance, you may want to look into low-oxalate alternatives for your next cup of coffee or tea (be sure to check out the article Oxalates in Tea). Most herbal infusions make a good low-oxalate alternative.
Parsley. On an ounce-to-ounce basis, there are few foods that contain more oxalates than parsley. According to USDA data, a 100-gram serving of fresh parsley provides 1700 milligrams of oxalic acid. However, considering that most of us use parsley only in small amounts to add flavor to dishes, this culinary herb is not likely to contribute much oxalic acid to your diet.
Chives. Like parsley, chives are generally only used in small amounts in cooking. Therefore, chives are not likely to contribute much oxalic acid to your diet, despite the fact they are among the most concentrated dietary sources of oxalates. A 100-serving of chives is estimated to provide 1480 milligrams of oxalates.