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本帖最后由 胡须康 于 2013-9-11 23:24 编辑
好复杂，
很久很久 以前所有的牛都是纯A2，后来产生基因变异，出现了A1的奶牛。
至于A1和A2的区别，和过敏，糖尿病什么的都有关，具体见下文。
In brief, this is the story. Originally, all cows worldwide (in Europe, Africa and Asia) were pure A2. Some thousands of years ago a natural genetic mutation occurred in a European herd, whereby the cows began producing milk whose casein had a very slight difference from the original. The effect of this difference is that an opioid (opium-like substance) is produced in the drinker's digestion process that is able to pass through the wall of the digestive tract and enter the bloodstream, from where it is able to reach the brain and other organs. This canot happen with milk from the original a2 cows.
With very minor exceptions, every cow has basically two genes that govern this issue. Either they are both A2 (meaning they produce pure A2 milk) or they are one A1 and one A2 (meaning the milk contains half A1 and half A2) or they are pure A1. Many herds in Europe, North America and Australasia which have been bred from European breeds such as Holstein and Friesian now have a mixture and are roughly half A1 and half A2, but a few (eg Guernsey) are still virtually pure A2 because they have not been interbred much. Cows in Asia and Africa are still basically A2. So are goats. And so are human beings. The milk produced by a human mother is pure A2, even if she drinks a1 milk. A2 milk is obviously what is right for babies and human beings, especially when young.
For many years, no one realised all this. Scientists knew there was a distinction between A1 and A2 (and thought A1 was the original one) but didn't give it much significance. Then some years ago, researchers noticed that the countries with high rates of coronary heart disease and type 2 diabetes are the countries where the dairy herds contain a high rate of A1 cows. The correlation is very strong indeed. But of course this doesn't prove cause and effect. And no one could quite explain it scientifically at that time, so the skeptics, including dairy producers whose milk contained A1, said it was pure coincidence. Since then, however, quite a lot of chemico-medical research has been done, which has increasingly substantiated the hypothesis that there is a cause and effect relationship. It would appear that either the opioid from A1 milk triggers certain health conditions (including schizophrenia and autism) or it lowers immunity to them. Of course, dairy producers whose milk contains A1 still dispute this, saying a cause and effect has not yet been 100% proved. A bit like the tobacco companies said for decades that there was no absolute proof that smoking caused lung cancer, even though there seemed to be a link. Absolute proof is hard to establish. It may likewise take decades with A1/A2. But the evidence is strong, and is growing. Food safety authorities say they are not yet advising people to avoid A1 milk but the evidence is certainly of interest and more research is needed. They are not discounting it.
Useful information on all this can be found at the website www.a2corporation com, which is run by the company with patent rights to the method of identifying A2 cows. It was set up by the scientist who did original work on this topic. You might say that since they are making money from this, we shouldn't put too much trust in them. But why shouldn’t they promote and derive benefit from their research? No one has proved them wrong. There's also a book by a very respected professor of agricultural management that sets out the science of this matter in terms easily understandable to the general public: Keith Woodford: Devil in the Milk. It also explains some of the politics involved, and why some interested parties (mainly the international dairy industry) are trying to play the issue down. He has also written other papers on this topic.
I hope this is helpful. I'm not a scientist but I've read up about this. And I drink only A2 milk.
Nick Turner
Source(s):
http://www.a2corporation.com/index.php/page/14
This is the science section of the website of the company owning the A1/A2 identity patent.
There are also papers by Prof Keith Woodford, who has researched this topic extensively:
http://keithwoodford.wordpress.com/category/a1-and-a2-milk
http://www.lincoln.ac.nz/Documen ... betes_be_s14210.pdf
An important paper by Prof Boyd Swinburn some seven years ago for the New Zealand Food Safety Authority, analysing the evidence existing at that time. It is still of interest, a
http://www.nzfsa.govt.nz/policy- ... lk/a1-a2-report.pdf |
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北印印象. (2017-8-29) xeh060 
来说说我的差旅生活，顺便聚点人气 (2005-7-17) ANDERSON999 
楼主:狄仁杰
发表于 2013-9-9 17:44
A2
发表于 2013-9-12 00:20
