Hi Karen

This paper suggests that B12 metabolism in athletes is altered and that athletes might need more B12 than sedentary people: http://tinyurl.com/35gthg

This paper shows that homocysteine rises during exercise and stays high for some time after exercise in some people: http://tinyurl.com/2oze2q

Don't know about non-physical stress. My PN was (and still is but to a much lesser extent) affected by strenuous exercise. My hypothesis is that my nerves are still damaged and are still sensitive to high levels of HCY or MMA or some other toxin that is produced during exercise.

If you search pubmed for Herrmann M or Herrmann W you will find many more papers on homocysteine and B12. They seem to be among the world experts, although they seem to be concentrating now on HCY and cardiovascular disease because that is much more common than PN.

Regards

Martin