So, how harmful is it? There are two popular sayings: (1) wastes calcium in tofu; (2) The combination of oxalic acid and calcium will lead to kidney calculi.
There is no doubt that the combination of oxalic acid and calcium precipitation will indeed waste some calcium. It is true that some elderly friends reported that after eating spinach and tofu, they went to the hospital for testing and found that oxalate crystals in urine increased.
However, another aspect of the problem is: if you don't eat it with tofu, won't the oxalic acid in spinach be absorbed? After absorption, won't it affect calcium utilization and promote the formation of stones? If you are worried about oxalic acid, can't you eat spinach? Then, there are many other vegetables rich in oxalic acid in the diet, such as bamboo shoots, water spinach, auricularia, amaranth, cowhide, water bamboo, green garlic, etc., which may also bring the problem of increasing oxalate. Are they also inedible?
Moreover, since oxalic acid in these foods can combine with calcium, can it not be eaten with soy products? Can't other foods rich in calcium be eaten with them, such as sesame sauce, milk, shrimp skin, seafood, nuts, and so on?
To analyze these problems, we can consider them from four aspects.
First of all, can oxalic acid be removed? Without oxalic acid, all the problems would be solved. Whether spinach and tofu will cause trouble depends first on how this dish is cooked. If spinach is directly fried with tofu without boiling water, it is indeed possible to increase the absorption of oxalic acid. Experiments show that the spinach after blanching has a smaller increase in urinary oxalate than the spinach directly fried. When blanching, it is necessary to use more water and drain enough water to fully remove oxalic acid. Stir-fry the tofu first, then add the blanched spinach, turn it over a few times, and the trouble caused by oxalic acid can be greatly reduced, and the delicious spinach tofu can be maintained.
Secondly, it depends on the total amount of oxalic acid consumed in a day. If spinach is cooked, but besides spinach, other vegetables containing a lot of oxalic acid are eaten, together, it may still bring the problem of excessive oxalate and increase the oxalate content in urine.
Third, look at the state of digestion and absorption function and acid-base balance of human body. Intestinal dysfunction will increase the body's absorption of oxalate intake, and physical acidity will also promote the formation of oxalate crystals. Studies have proved that although the content of oxalate is high in vegetarians without animal protein, the risk of stones in vegetarians is very low; Eating too much meat, polished rice flour and sugary foods will promote the body to be acidic, thus increasing the risk of stones.
Fourth, whether eating vegetables rich in oxalic acid together with tofu will increase the risk of stones. The medical investigation in our country proves that taking more calcium is beneficial to prevent the formation of stones in kidney and urethra. That is to say, after eating spinach, if you don't eat bean products rich in calcium, the risk of stones is even greater. American experts even suggested that it is best to eat high-calcium food and oxalic acid food together to promote the precipitation of oxalic acid in the intestine and avoid being absorbed by the human body in large quantities.
In fact, tofu rich in calcium and protein, together with blanched spinach rich in vitamin K, potassium and magnesium, is a perfect match for supplementing calcium and strengthening bones!
This article is transferred from Sohu Health Blog: Original Nutrition Information