Hi there Howard
Good on you for doing some research....
Your doctor is advising you to take fish oil or flax seed oil due to the essential fatty acids in both of these supplements.
Here are some facts about Essential Fatty Acids:Several studies show that men who eat fish several times a week have less heart disease than men who don't eat fish regularly. Other studies show that fish oil supplements can help prevent sudden death from heart rhythm problems. Fish oil supplements may also prevent blood clots from blocking the arteries leading to the heart
Apparently there was one study documented in the American Journal of Clinical Nutrition which showed the flax seed oil supplements actually increased the incidence of prostate cancer!!
I found this site, which shows some information about that report and a response from a doctor -
Flax Seed and Prostate Cancer.
Do some more research on the internet and remember that this is one study, albeit it is an important one. Only take information from reputable sources (ie medical journals, universities, health organisations, etc). Look at stuff from people's own sites, but remember that everyone is different and what worked for one person may not be best for you...
In any case, you should try to eat lots of fresh fruit and vegetables... for their vitamins, minerals and especially antioxidant content.... which all help with health in general.... antioxidants help with heart problems, in particular...
I am sure you know all the things you should not do, so I wont repeat them, but if you want any further info, let me know.
In any case, you should go back to your own doctor and talk to him/her about what you have read, your family's high prevalence of prostate cancer, your high blood pressure problems and discuss your options... because you do have options...
PS - I am not a doctor, nor am I a health professional, I just have a major interest in health and nutrition, with a view to gaining post-graduate studies in this area...