In the past, it was believed that spinach should not be eaten with tofu. There was only one reason: spinach contains a large amount of oxalic acid, which will combine with calcium to form an insoluble precipitate.
However, this statement fails to see the other side of the problem - spinach also contains a variety of substances that promote calcium utilization and reduce calcium excretion, including rich potassium and magnesium, as well as vitamin K.
Everyone knows that calcium is closely related to acid-base balance. When excessive intake of protein foods leads to an acid-base imbalance, the body's calcium excretion will increase. At this time, if you can eat more green leafy vegetables, such as spinach, you can fully absorb potassium and magnesium, help maintain acid-base balance, and reduce the amount of calcium excretion, which is very beneficial to bone health.
100 grams of spinach contains 311 mg of potassium and 58 mg of magnesium, ranking first among vegetables, 2.7 times the potassium content of apples and 11.6 times the magnesium content. With the rich potassium and magnesium in spinach, the calcium in tofu can be better retained in the human body.
What’s more worth mentioning is that the vitamin K in spinach has a powerful effect in promoting the formation of bone calcium. Vitamin K is one of the hot topics in nutrition research in recent years. It is an essential component for the formation of "osteocalcin".
Vitamin K is mainly found in green leafy vegetables and vegetable oils, and spinach is one of the vegetables with the highest content, second only to kale, with a content of 415 micrograms/100 grams.
Survey data shows that middle-aged and elderly women whose daily intake of vitamin K is more than 109 micrograms can reduce the risk of fractures by 30%. There are also studies that prove that supplementing 200 micrograms of vitamin K every day can maintain and improve bone density. In fact, you only need to eat less than 100 grams of spinach a day to achieve this effect.
Studies have shown that if vitamin K is added while supplementing calcium, the effect of calcium supplementation can be greatly improved and calcium deposition into bones can be promoted. Tofu, which is rich in calcium and protein, and spinach, which is rich in potassium, magnesium and vitamin K, are the perfect combination to supplement calcium and strengthen bones.
So, what to do with the oxalic acid in spinach? Since oxalic acid is very soluble in water, more than 80% of the oxalic acid can be removed by blanching the spinach in boiling water for 1 minute and taking it out. Fry the tofu first, then add the blanched spinach, and it will be fine if you mix them together.
Fortunately, vitamin K is not sensitive to heat and is not soluble in water, so blanching spinach will not cause its loss. However, vitamin K, like carotene, requires oil to help absorb, so when making spinach and tofu soup, be sure to add some oil.
Spinach stewed with tofu is rich in nutrients, high in quality and low in price. It is a traditional Chinese delicacy. Although spinach contains a large amount of oxalic acid, which can form calcium oxalate precipitation with the calcium in tofu and hinder the body's absorption of calcium, everything has its two sides.
When you eat spinach alone, the oxalic acid in it will combine with some of the iron and zinc in the chyme in the stomach, and the oxalic acid can also enter the blood and precipitate the calcium contained in the blood. When tofu and spinach are eaten together, the calcium in tofu combines with the oxalic acid in spinach, which can protect the iron, zinc and other elements in the food, and also ensure that the calcium in the human body is not combined by oxalic acid.
Therefore, eating tofu and spinach together is still a good combination. Of course, if the proportion of spinach can be appropriately reduced during cooking and the spinach is blanched in advance, the absorption rate of calcium in tofu will be significantly improved.
How to make spinach and tofu
The spinach is green, the tofu is golden, and the soup is hot and refreshing. Many people like to eat spinach. Spinach is very good whether stir-fried, mixed, roasted, made into soup or used as an ingredient. However, spinach contains oxalic acid, which affects the body's absorption of calcium after eating. Therefore, you should first eat this kind of spinach. Blanch thoroughly to reduce oxalic acid content.
Ingredients: 400g spinach, 400g tofu.
Seasoning: 50 grams of salad oil, 6 grams of salt, 3 grams of MSG, 8 grams of sesame oil, appropriate amounts of each.
Steps to make spinach stewed tofu:
1. Remove the spinach leaves, use only the root and stem parts, cut it into quarters in a cross shape, wash it, and put it into a pot of boiling water. Blanch to remove astringency, remove and drain.
2. Cut the tofu into cubes, fry it in 60% hot oil until golden brown, take it out, put it in a casserole, add about 400 ml of clear soup, refined salt, and MSG, and cook over low heat until the tofu becomes golden brown. Add in the flavor and add spinach and sesame oil.