What are the physiological effects of mindfulness based meditation? I was meditating on the breath recently and I noticed that my breath slowed to a significant extent (not a huge insight admittedly). So this made me wonder if anyone has measured the effects of mindfulness type meditations on the body while the person is meditating. For instance what is the affect on breath rate, blood pressure, heart rate, the hormonal system and so forth.
This is a bit technical, but shows the positive effects from meditating in some key hormones we produce related to health and stress. I was discussing it with my girlfriend (she is endocrinologist and not buddhist) and she was quite surprised with it.

If you want you can skip to the end of the text to see the conclusion


  " Previous studies of the Transcendental Meditation (TM) technique as
  a possible means of countering effects of stress have reported altered
  levels of several hormones both during the practice and longitudinally
  after regular practice of this technique. In this prospective, random
  assignment study, changes in baseline levels and acute responses to
  laboratory stressors were examined for four hormones-cortisol, growth
  hormone, thyroid-stimulating hormone and testosterone-before and after
  4 months of either the TM technique or a stress education control
  condition. At pre- and post-test, blood was withdrawn continuously
  through an indwelling catheter, and plasma or serum samples were
  frozen for later analysis by radioimmunoassay. The results showed
  significantly different changes for the two groups, or trends toward
  significance, for each hormone over the 4 months. In the TM group, but
  not in the controls, basal cortisol level and average cortisol across
  the stress session decreased from pre- to post-test. Cortisol
  responsiveness to stressors, however, increased in the TM group
  compared to controls. The baselines and/or stress responsiveness for
  TSH and GH changed in opposite directions for the groups, as did the
  testosterone baseline. Overall, the cortisol and testosterone results
  appear to support previous data suggesting that repeated practice of
  the TM technique reverses effects of chronic stress significant for
  health."


source http://www.ncbi.nlm.nih.gov/m/pubmed/9226731/