Spinach is rich in nutrients, known as the "king of vegetables", but spinach contains a lot of oxalic acid (about 300 mg of oxalic acid per 100 grams of spinach). Tofu contains more magnesium chloride, calcium sulfate, both of which, if entered the body at the same time, will generate insoluble calcium oxalate, which will not only cause calcium loss, but also may be deposited into the stone. So it is best not to eat spinach and tofu together. In fact, spinach does not contain the highest amount of iron, but also can not supplement blood, because spinach only 10% of the iron absorbed in the intestines, the other 90% are combined with oxalic acid into insoluble substances, not only difficult to absorb, but also affects the absorption and utilization of iron in the human body, it is not advisable to eat spinach alone too much at a time.