区别乳糖不耐受症和牛奶过敏 Lactose Intolerance versus Milk Allergy

http://www.90life.com/n5581c16.aspx

        原因有两种，一是乳糖不耐受，一是牛奶过敏。

        乳糖不耐受 乳糖必须经过体内乳糖酶水解为葡萄糖和半乳糖才能被人体吸收。但是有些人体内小肠黏膜无法产生足够的乳糖酶，当饮用奶类后，乳糖未被分解，直接到了大肠。在肠道细菌的作用下，乳糖发酵和分解，产生大量气体和有机酸刺激肠黏膜导致腹泻。

        乳糖酶缺乏分先天和后天的。比如宝宝出生后发现缺乏不能和奶，这类患儿可以用米汤、无乳糖或乳糖含量低的配方奶粉。

        后天缺乏，多数由于长时间没有喝牛奶，机体合成乳糖酶的功能退化或疾病原因，导致乳糖酶分泌不足或缺乏。解决办法是，少量多次，渐渐适应，慢慢的消除乳糖不耐受，提高小肠黏膜合成乳糖酶的能力。

        牛奶过敏。表现为出现呕吐、腹痛、腹泻、大便稀，有时带血。往往还出现湿疹、寻麻疹、哮喘等等症状。原因是牛奶中蛋白质通过肠黏膜上皮，使黏膜下的免疫细胞发生过敏。

       针对过敏有2个办法，一个是改吃其他的代乳品，一个是脱敏疗法。

http://www.epochtimes.com/gb/6/8/9/n1416152.htm

       【乳糖酶缺乏，极少与生俱来】
        乳糖酶缺乏可分为两大类：先天性和后天性。后天性的包括继发性和成人型乳糖酶缺乏。

       先天性乳糖酶缺乏——出生时体内即无乳糖酶，无论饮用母乳、牛乳均可导致明显腹泻，停止喂养乳类或以米汤类食物代替，腹泻则消失。这种情况很少见，可能与遗传有关。

       继发性乳糖酶缺乏——常发生在一些疾病之后，如感染性疾病、严重的营养不良等；或由于某些药物的作用，造成小肠黏膜受损，导致乳糖酶生成障碍。

       成人型乳糖酶缺乏—— 绝大多数乳糖不耐受者均属此类。他们出生时体内乳糖酶并不缺乏，长到一定年龄，才开始出现乳糖酶活性的逐渐下降或消失，并导致乳糖不耐受。有关研究认为，成人型乳糖酶缺乏，与世代相传形成的不同饮食习惯所造成的遗传基因突变有关，因此它的发生率也因民族和地区不同而异。我国大多数儿童从7～8岁开始出现乳糖酶缺乏，欧美国家的人20岁左右才开始出现。世界上完全没有乳糖不耐受的人仅占３０％左右。

       【简单战术，喝奶“难受”变“享受”】
牛奶是营养最全面、最容易被人体吸收的食品。因乳糖不耐受而不喝牛奶实在太可惜。其实，完全可以变个法子喝牛奶。

       “偷袭”—— 少量多次，渐渐适应　乳糖不耐受的发生往往与一次摄入乳糖量过多有关，不耐受的程度也存在明显的个体差异。可根据自己的实际情况，分多次少量进食牛奶，每次的量应限制在能够耐受的水平。待适应后，量可逐渐增加，次数减少。这样不仅可以减轻或避免乳糖不耐受，而且可刺激和提高小肠黏膜合成乳糖酶的能力，逐渐消除乳糖不耐受症。

       “夹攻”——混合膳食，延缓胃排空　避免空腹单独喝牛奶，适当选择一些其他食物一同进食，最好是固体食物及吸收较慢的食物（如面包、饼干等），也可以在吃饭时喝一小杯牛奶或将牛奶加入麦片粥中食用。混合膳食使乳糖得到稀释，也避免牛奶迅速从胃里排空，从而减缓乳糖的转运，减轻乳糖不耐受症状。

       “伪装”——用酸奶代替牛奶　酸奶是用牛奶加入乳酸菌发酵生成的。在发酵过程中，牛奶中20％～30％的乳糖被分解，蛋白质和脂肪也得到了分解，利于消化吸收。因此，乳糖不耐受者能更好地耐受酸奶。

       “持械” —— 添加乳糖酶　目前，世界上不少国家已经采用在牛奶或奶类制品中加入乳糖酶制剂来治疗乳糖不耐受症。这一类酶制剂是利用乳酸杆菌或酵母菌所含有的乳糖酶制成的，使乳糖在食用前就被消化，可以显著减轻不耐受症状。也可以在喝牛奶时，先吃一片乳糖酶，同样起到预防或减轻乳糖不耐受的作用。

       对于先天性乳糖酶缺乏所引起的新生儿、婴幼儿的乳糖不耐受，治疗较为困难。而且母乳或牛奶又是其主要的营养来源。这类患儿可选用不含乳糖的配方奶粉。对于继发性乳糖酶缺乏所引起的乳糖不耐受，则要在治疗原发疾病的同时，选用不含乳糖的配方奶粉，减轻肠黏膜的负担，让肠黏膜逐渐恢复功能。简单几招，可减轻或消除乳糖不耐受症状。天天喝牛奶，享受牛奶带来的健康。

       【什么是乳糖不耐受】
乳糖是奶类中特有的糖，每100毫升鲜奶中大约含5克乳糖。乳糖需经体内乳糖酶水解为葡萄糖和半乳糖才能被吸收。但由于有些人体内的小肠黏膜无法产生足够的乳糖酶（即乳糖酶缺乏），当饮用奶类后，乳糖未能被分解，便从小肠直接转运到大肠，在肠道菌的作用下，乳糖被发酵和分解，产生大量气体和有机酸，刺激肠道黏膜，导致腹胀、肠鸣、腹痛甚至腹泻，有些人还会有嗳气、恶心等。这种情况一般称为乳糖不耐受或乳糖吸收不良。

http://ourworld.compuserve.com/homepages/stevecarper/livallg.htm

Lactose Intolerance versus Milk Allergy

 

More people ask me if Lactose Intolerance (LI) is the same thing as an allergy to milk or dairy products than any other question. They are not the same; they are not even related. Here are the basics on how to tell them apart.

Lactose Intolerance

People who have LI cannot digest the milk sugar, lactose, because they manufacture too small a quantity of the digestive enzyme, lactase. Too small is a relative term. If you drink only tiny amounts of milk, even a tiny amount of lactase is sufficient. Too much milk (or any dairy product) can overwhelm even a fairly large lactase supply. How much is too much? That depends on a dozen factors, and can be hard to judge, even from meal to meal.

Undigested lactose sits in the intestines and does two things, both bad. It draws water into your intestines, producing diarrhea, and it gets fermented by the bacteria in your colon, producing gas. That's why the symptoms of LI include, in addition to gas and diarrhea, flatulence, bloating and cramps. Note that these are all symptoms of the lower intestines. Anyone (except for young children) who gets vomiting, burping, heartburn, or other stomach ills, should look for a difference cause.

Food can take 12 hours to two days to completely pass through your intestines. That's why symptoms can last for a long time and that's why it can be hard to pinpoint exactly which foods are bothering you. Symptoms can also start almost immediately after eating dairy. This is not because the dairy has hit your intestines, but because food in the stomach triggers what is called peristalsis in the intestines, the muscle movements that push food through. If you are already suffering from excess gas and water, you can feel the pressures of diarrhea long before any new food has a chance to leave the stomach.

LI is a normal part of aging for the vast majority of people around the world, but it can also be caused by anything (disease, drugs, surgery) that damages the intestines. This is called Secondary LI. It can be temporary, clearing up when the disease goes away or the damage heals, or, in adults, especially, it can be permanent.

Infants, whose intestines are still delicate, are especially vulnerable to Secondary LI. A "stomach flu" or any prolonged bout of diarrhea can knock out their lactase-making ability. They need to be taken off all milk (both breastmilk and milk-based formula) until their intestines can heal. this can be for several weeks. Fortunately, nearly all babies will be able to drink milk normally once healed.

Milk or Dairy Allergy

A milk or dairy allergy is a reaction to the protein in milk. There are two milk proteins, casein and whey. Some people are allergic only to one or the other. Most are allergic to both. The safest course in either case is to avoid all dairy products.

This is very different from LI, in which most people can still have small or moderate amounts of milk. What's the difference? An allergy is an immune system reaction. Your immune system fights foreign invaders to the body using what are called antibodies. When these invaders are harmful bacteria or viruses, this is a very good thing. In people with allergies, however, the immune system reacts in the same way to dairy proteins that leak into the bloodstream instead of being properly digested. This can lead to a huge number of possible symptoms.

And a great deal of confusion. You see, the body contains more than one type of antibody. True allergies are caused (technically, mediated) by Immunoglobulin E (IgE). These are the dangerous ones, the ones that can cause people to get hives all over their bodies, or have trouble breathing, or, in the worst cases, go into anaphylactic shock and die. Fortunately, true allergies are extremely rare, affecting only a percent or two of the population.

But all those other antibodies can also cause reactions. These are also sometimes called allergic reactions, and this is the source of much of the confusion. (It is only recently that doctors began to understand the differences themselves and so too much of the old and obsolete terminology is still hanging around.) You'll sometimes see references to protein intolerance, even though it is nothing like lactose intolerance. The best name is hypersensitivity.

No matter what name is goes under, a protein hypersensitivity is easy to confuse with LI. They both are likely to cause problems in the intestines. But in addition to gas and diarrhea, they also can cause vomiting or colic.

Children are the most likely sufferers of both allergies and hypersensitivities. Even breast-fed babies who have never touched formula can suffer from allergies, because dairy proteins can leak into the mother's milk. And even if this does not happen, they can rapidly develop allergies after their first exposure to milk-based formula or milk itself. (I'm assuming cow's milk, but this is also likely to be true for goat's or any other type of milk.) Most babies will thrive on soy-based formulas or milks, and there are other non-dairy alternatives for those rare few who are also allergic to soy.

Still confused? Here's a chart to highlight some of the differences in babies. (It sometimes happens that the symptoms first appear in older children or even adults, but the basics of the chart are true for them as well.)