人体中的钙，99%存在于骨骼和牙齿中。婴幼儿时期缺钙，就容易形成“O”型腿或“X”型腿。严重畸形的孩子，长大后不得不做矫形手术。
In the human body, 99% of calcium exists in the bone and teeth .Insufficient intake of calcium for infants may leads to varus or valgus knee deformity. Children with serious knee deformity have to take corrective surgery when they grow up.
“O”型腿：两踝关节并拢，膝关节不能并拢（上图左）。
Varus knee deformity: the knees can’t put together if the two ankles are (as shown in the left picture)
“X”型腿：两膝关节并拢，踝关节不能并拢（上图中）。
Valgus knee deformity: the ankles can’t put together if two knees are (as shown in the middle picture)
一、缺钙的表现
Calcium Deficiency Symptoms
孕妇的腿出现抽筋，就说明缺钙了。母亲缺钙，孩子必定缺钙。
Cramp in calf muscles is a symptom of calcium deficiency for pregnant women. Calcium deficiency of a mother will result in calcium deficiency of her baby.
有的家长说孩子胆小，睡觉时稍微有点儿动静，胳膊一抖就醒了。
Some parents say their babies are easily scared by some minor noise when they are asleep, and a sudden shake of their stretched arms is usually the babies’ reaction to the minor noise.
还有的家长说孩子放不下，抱在怀里感觉睡实了，小心翼翼地往床上一放，“哇”的一声又哭了。
Some other parents say their babies sleep well in their arms, but will wake up easily if they put the babies onto bed, usually with the loud baby cry.
其实，这就是缺钙了。因为钙维持着神经肌肉的兴奋性，缺钙了神经肌肉的兴奋性增高，就容易激惹。
In fact, the reason is calcium deficiency. Calcium maintains the level of neural muscle excitation, and calcium deficiency will cause the increasing of neural muscle excitation. That’s why the babies are easily scared.
缺钙还引起多汗，汗的刺激使得枕部瘙痒，孩子不停地摆头，头发慢慢磨掉，形成枕秃（如上图）。
Calcium deficiency will also cause a lot of sweating. Sweating will arouse itch of the pillow part of the head. So babies will shake their heads frequently, which will result in alopecia (as shown in the above picture).
二、缺钙为什么会抽搐呢？
Why Calcium Deficiency Causes Cramp?
钙维持着神经肌肉的兴奋性。血液中钙的浓度低了，位于颈部甲状腺旁的甲状旁腺（如下图）就会分泌升钙素，把骨骼中的钙脱出来，优先维持生理功能。
Calcium maintains the level of neural muscle excitation. When human blood calcium level decreases, the parathyroid gland (as shown in the picture below), which is in the neighborhood of the thyroid in the neck, will secrete parathyroid hormone (PTH). PTH will remove calcium from the bone to keep the calcium level in the blood, maintaining the normal metabolism of the body.
当甲状旁腺功能降低时，升钙素分泌不足，从骨骼中脱出的钙不足以维持正常生理机能时，就会出现抽搐。
When the functioning of the parathyroid decreases, there will be insufficient PTH secreted and Cramp will occur if the PTH removed from the bone can’t keep the normal metabolism.
在一定程度上，抽搐是件好事。因为抽搐必然导致就医，而如果甲状旁腺功能正常，骨骼中的钙源源不断地流入血液，骨骼慢慢变软，最终不堪重负，导致骨骼畸形。
Cramp is kind of good to some extend because people go to hospital if cramp happens. However, if the parathyroid functions well, calcium in the bone will be transferred continually to the blood. As a result, the bone will be softened and eventually become deformed due to the heavy load.
三、如何科学补钙？
How To Make Calcium Supplement Scientifically?
人的皮肤中有一种物质（7-脱氢胆固醇），在紫外线照射下转化成维生素D，维生素D能够促进肠道对钙的吸收，所以婴幼儿应该多晒太阳。
There is a substance called 7-dehydrocholesterol in human skin, which can be transformed into vitamin D in ultraviolet radiation. Since vitamin D helps the intestine absorb calcium, so babies should often bask in the sun.
玻璃能把太阳光中的紫外线过滤掉，隔着玻璃晒太阳是无效的。
Glass will block the ultraviolet radiation, so it’s useless to bask in the sun through glass.
维生素AD滴剂，含维生素A和D，这两种维生素都是脂溶性维生素，不溶于水，不能从尿里排出，长期大量使用有中毒的危险。
Vitamin AD drops contains both vitamin A and D. These two vitamins are fat-soluble and can’t dissolve in water, so it can’t be released in the urine. Therefore there’s a danger of being poisoned if taking vitamin AD for long time.
维生素A用于治疗夜盲症。单纯为了补钙用维生素D更安全，不用担心维生素A中毒。
Vitamin A is used to treat nyctalopia. If the purpose is only to help calcium absorption, then it’s safer to take vitamin D, without worries of vitamin A overdose.
总之，维生素D是促进钙吸收的，补钙的同时增加体内维生素D的含量，将会大大提高钙的吸收率。
In conclusion, vitamin D helps calcium absorption. The calcium absorption rate will be greatly increased if people raise the vitamin D amount in their body.
英文翻译：张颖楠
