I
am convinced that MAP is implicated in Crohns, but ironically enough I agree with those who are not, I actually wouldn't worry too much about
milk products on that basis.
First of all, like everything else in biology it is a numbers thing. MAP is not very good at infecting humans, or it would be found in everyone, CD patients or not. Since it is not, and since if it is a causative agent in CD the most active form is lurking in the macrophages already, unless you get milk that contains very high numbers of the bacteria the additional overall effect is likely to be zero. Theoretically what happens when you pool the milk from 500 or more healthy cattle with that from a couple of MAP infected animals is that you bring the risk from high for a very limited number of people drinking milk from infected animals, to very low but present for a much higher number of persons; so given enough time and the presence of more of hosts with the right genes, many more people are likely to become infected.
Look at the proteins in different forms of milk however and you suddenly realise that cow's milk is very unnatural food for humans. Think of it this way - our bodies are adapted to human breast milk, and it is designed in effect to be good for small omnivores weighing several pounds and whose brains and immune systems develop for more than a decade. Cow's milk has only been available to humans for a tiny fraction of the time we have been here - how long before stone age man started catching and taming something like wild buffalo ? - and is designed for a herbivore with five stomachs and an IQ that is barely measurable, which reproduces at the age of two years. There is no doubt that many many humans, far more than are ever affected by MAP, have adverse immune system responses to the proteins in cow's milk. Goat's milk is designed for a much smaller, very indiscriminate omnivore (which may be the reason the proteins are more like ours), which has probably been co-evolving with humans for longer, and it is known in some crucial ways the proteins are very different to cows milk in terms of the immune response they provoke. (Not kidding here, fruitgirl !
) Lactose is the least of the problems. ( A side issue here is there is a theory that our modern higher incidence of CD is related to a particular genetic variant of cows milk, found more recently in the Western world but not in older breeds as found in Africa. This makes sense if cows were first tamed in Africa - evolution has had more time to screen out disease-prone hosts. )
Interestingly, when a young boy my father found cow's milk was making him ill. The medical treatment in the 30s ? Get a goat and give him goat's milk for a couple of years...he has never had problems since, even with cow's milk products.
So never mind MAP or Crohns, why use cows milk anyway ? If it wasn't so common, we just wouldn't, it is so firmly associated with so many things like asthma, eczema, psiorasis, etc. Like soya, it is a food that where the producers have got together and invented ways of using it, with their only aim being increased output and profits; safety is not their professional concern, except where it impinges on sales. The idea that the calcium in it is good for you is a marketing myth too - it is there, but not easily available to humans, although convincing most folk of that is about
as easy as dispelling the myth that Chinese have been drinking soya milk daily for 3000 years. (Fermented because it was so indigestible, in famines or as medicine only.)
As far as taking 40 years to prove MAP is a causative agent - Crohns is a 20th century malady, really only noticed in 1938. TB was been around for 2000 years, infecting and usually killing 1 in 12 of the population
but how long did it take to prove the causative agent there, even once Koch and his genius friends invented microbiology ?
Right until the 40s, there was a debate about
the cause of TB that was uncannily similar to that on Crohns. That may just be typical of any high-profile disease of course, but it may be indicative of hidden similarities in the topic in question.
If it takes 16 months to produce a new generation of your research subject in a laboratory, it fairly cramps your style, and hinders what questions may be investigated. What takes E. coli researchers a day with replication every 20 minutes, would take decades at that rate.
I wouldn't say the jury is out, we don't even have all the evidence yet for a prosecution - but we have at least one good suspect to question.
