It's actually for the same reason people get sick when the visit countries with poor water quality and drink the water. They aren't used to the pathogens.
Check page 2 of this Consumer Reports article[1] for an example.
> Enterococcus was the most common bacterium we found, occurring in 79.8 percent of our samples. Next was E. coli, in 65.2 percent of them; campylobacter, 43 percent; klebsiella pneumoniae, 13.6 percent; salmonella, 10.8 percent, and staphylococcus aureus, 9.2 percent.
It's part of the reason that only some people experience the problems as a lot of it depends on how long you have not eaten meat, at what age you stopped eating meat, the overall strength of you immune system and just if you were unlucky the first time you resumed eating meat and ate something with higher percentage of pathogens present. Also, if you regularly cooked and ate from a kitchen that was mixed use or non meat.
Check page 2 of this Consumer Reports article[1] for an example.
> Enterococcus was the most common bacterium we found, occurring in 79.8 percent of our samples. Next was E. coli, in 65.2 percent of them; campylobacter, 43 percent; klebsiella pneumoniae, 13.6 percent; salmonella, 10.8 percent, and staphylococcus aureus, 9.2 percent.
It's part of the reason that only some people experience the problems as a lot of it depends on how long you have not eaten meat, at what age you stopped eating meat, the overall strength of you immune system and just if you were unlucky the first time you resumed eating meat and ate something with higher percentage of pathogens present. Also, if you regularly cooked and ate from a kitchen that was mixed use or non meat.
[1] http://www.consumerreports.org/cro/magazine/2014/02/the-high...