Once upon a time, it was thought that spinach should not be eaten with tofu for one reason: spinach contains a lot of oxalic acid, which can combine with calcium to form an insoluble precipitate. However, this argument fails to see the other side of the coin -- spinach also contains a variety of factors that promote calcium utilization and reduce calcium excretion, including abundant potassium and magnesium, as well as vitamin K.
It is well known that calcium is closely related to acid-base balance. When protein foods are consumed in excess, the acid-base balance is imbalanced, and the body's calcium excretion will increase. At this time, if you can eat more green leafy vegetables, such as spinach, you can fully intake of potassium and magnesium, to help maintain the acid-base balance, reduce the number of calcium excretion, on the bone health is very beneficial. 100 grams of spinach containing potassium 311 mg, containing 58 mg of magnesium, in the vegetables in the top, is Fuji apple potassium content of 2.7 times, magnesium content of 11.6 times. With the abundance of potassium and magnesium in spinach, the calcium in tofu is better able to stay in the body.
What's more, the vitamin K in spinach has the powerful effect of promoting bone calcium formation. Vitamin K is one of the hotspots of nutritional research in recent years, and it is an essential component in 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 suggests that middle-aged and older women with a daily intake of 109 micrograms or more of vitamin k have a 30% lower risk of fracture. It has also been demonstrated that a daily supplement of 200 micrograms of vitamin k has the effect of maintaining and improving bone density. That means you can achieve this effect by eating just under 100 grams of spinach a day.
Studies have shown that if you add vitamin K to your calcium supplementation, you can greatly increase the effectiveness of your calcium supplementation and promote calcium deposition into your bones. Tofu, which is rich in calcium and protein, and spinach, which is rich in potassium, magnesium, and vitamin K, are a perfect match for calcium and bone health.
What about the oxalic acid in spinach? Because oxalic acid is very soluble in water, simply blanch spinach in boiling water for 1 minute and fish out, you can remove more than 80% of the oxalic acid. Stir fry the tofu first, then put in the blanched spinach, and mix it in without a problem.
Fortunately, vitamin K is not afraid of heat and is not water-soluble, so blanching spinach will not cause it to be lost. However, vitamin k, like carotenoids, needs oil to help absorb it, so always remember to put some oil in when making spinach and tofu soup.