In milk, cheese, and yogurt, about 30% of the calcium is absorbed. This is a higher rate than beans, spinach, sweet potatoes and a lower rate than broccoli, kale, and bok choy. A plant's calcium bioavailability is affected by the presence of oxalate and phytate, two naturally occurring compounds that interfere with calcium absorption. Dairy foods contain neither.
As a general rule, the higher the oxalic acid in a food, the lower the calcium absorption rate. Therefore, calcium is poorly absorbed in Chinese and American foods varieties of spinach and rhubarb, intermediate from sweet potatoes, and high from low-oxalate vegetables such as kale, broccoli, and bok choy. Dried beans have a low bioavailability of calcium because they are rich in phytate.
Each cup of spinach contains approximately 250 mg of calcium. However, it is less easily absorbed than calcium obtained from dairy products. Spinach has a high level of oxalate, which binds to calcium.
Everyday foods that are high in protein but also high in calcium.
1 ounce grated Parmesan cheese (314 mg) 1 cup large-curd cottage cheese (126 mg), 8 ounces low-fat yogurt (415 mg), 8 ounces low-fat milk (340 mg), 1 ounce (1-inch cube) Swiss cheese (224 mg), 1 ounce (1 slice) Cheddar cheese (204 mg), 1 ounce mozzarella cheese (143 mg), 1 scoop (28 g) whey powder protein (110 mg).
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