From experience you don't have to be going for a medical to suffer from white coat syndrome. At my last place of work there was an excellent medical facility for the benefit of all employees and students (it was a university), and they had no part in my biannual medicals. Whenever I reported there for anything at all, a cold for instance, my blood pressure was taken. Results were usually in the 150/90 range and accompanied by much tut-tutting on the part of the doctor.
In the end I got my own blood pressure monitor and made detailed records of the results over a period of about six weeks. Next time I went I showed them to the doctor who immediately diagnosed me as having white coat syndrome. He admitted that about 20% of the population suffers from it.
Like a number of you I have an excellent AME with whom I get on well. I did the same thing with him at my last medical where his readings were around 140/85 and the average of mine was nearer 125/75. He actually wrote on the form that this more accurately represented my blood pressure.
I asked him what to do about lowering it since I have tried most things - decaffeinated coffee, regular exercise, healthy diet and I even gave up smoking. His answer surprised me a bit as he said to just eat, drink and be merry. I suspect that most AMEs don't worry too much about it unless the candidate is either seriously overweight or has something else majorly wrong with him/her. This would appear to rule out the majority of aircrew.
Bottom line I suppose is to lead as healthy a lifestyle as possible and to accept that the high stress we go through is on the medicals we are obliged to endure.