One of the dietary supplements after blood donation

　　 has made it clear that blood donation of 200 or 400 ml within one year only accounts for 5% to 10% of the total blood of adults, which is safe and harmless to healthy adults of. Therefore, even if nothing is added after the blood donation, the blood loss can be recovered within a period of time after the blood is donated. Of course, in order to promote recovery, it has become common practice to take corresponding "blood supplementation" measures after donating blood. The usual practice is to eat nutritious foods, especially some blood-enriching foods, such as jujube, fungus, longan, pork liver, eggs and so on. Some of these practices are not correct, and some are correct but not sufficient. How can blood be properly replaced after blood donation?

　　Let us first understand the composition of blood. Blood is mainly composed of four components, including plasma, red blood cells, white blood cells, and platelets. Plasma, which accounts for about 55% of blood, is a mixture of water, sugar, fat, protein, potassium, and calcium salts. It also contains many chemicals needed to stop bleeding. Red blood cells, white blood cells, and platelets make up another 45% of blood.

　　 Among these ingredients, the ingredients that directly source food are few or unimportant, most of them are synthesized by the body, and the raw materials are more common nutrients in food, such as protein and fat. It is easy to obtain from daily food, and generally does not require additional supplements, but there is an exception, that is the key raw material for the synthesis of hemoglobin-iron. It all depends on food supply, and the content and absorption rate in food are relatively low, and it is relatively easy to lack. You should pay attention to supplement after blood donation. Otherwise, you can only rely on the original iron reserve before blood donation (healthy adults store some iron in the spleen and liver for synthesis of hemoglobin). If the iron reserve before blood donation is not very sufficient, especially women, it is easy to cause Iron deficiency, if severe, can cause iron deficiency anemia, and iron deficiency anemia is one of the most common nutritional deficiencies, especially among children and adult women. Therefore, to a certain extent, the "blood supplementation" after blood donation is mainly to supplement iron, and to eat foods rich in iron.

The iron in plant foods (including grains, soy products, vegetables, fruits, fungi, algae, nuts, etc.) is "non-heme iron", which is characterized by low iron content and low absorption rate, generally It is 1% to 5%, and is easily affected by interference factors (such as dietary fiber in food, oxalic acid in vegetables, phytic acid in beans, polyphenols in tea, caffeine in coffee, etc.). Therefore, the effect of eating jujube, fungus, longan and other blood supplements is very poor. Calculated by donating 400 ml of blood, the hemoglobin content is 48 g (based on the normal hemoglobin concentration of 120 g/L), and the iron content of hemoglobin is 0.34%, so the total loss of iron from 400 ml of blood donation is 163 mg (48×1000×0.34%= 163). It is known that the iron content per 100 grams of dried jujube is 2.3 mg, and the absorption rate is calculated as 5%. If all the iron lost from 400 ml of blood is supplemented with jujube, you need to eat 141.7 kg of dried jujube (163÷2.3 ×100÷5%=141.7)! In practice, due to changes in physical conditions and recipes, it may not be completely consistent with the theoretical calculation, but the conclusion is very clear: it is completely unrealistic to rely on iron supplements by eating plant-based foods.