Heart Sutra
I have previously openly declared I am a male with an interest in the impact of omega six and omega three on a range of conditions, functions of the body etc. I am strictly amateur but do read widely. I am learning too. I do try and practice what I suggest, but could do better.
I had a relative who died of BC. I had a lump excised which was not likely to be BC but could have been and the experience was thought provoking.
RE your comment - "that an all encompassing dietary solution working for all people is rather unlikely"
Our bodies all function at a basic level in very similar ways. The food you eat alters the way you express your genes - the number of copies you switch on including HER2 and BRAC.
Trials on other issues such as cardiac health have shown in general terms people respond similarly to a low fat low protein "healthy" diet, (following general recommendations above).
Our modern diet breaks so many of the basic rules that we are not talking about fine tuning - this is about the basics. We have evolved / been designed to live in an environment with a range of diets, but those never included refined foods, high levels of sugars, salt, trans fats, vegetable oils. These push the body outside its design parameters. The consequence is a greatly increased of range of conditions.
There is a strong argument that better diet for those who eat high levels of refined food...... will reduce the risk for all [some more than others and on the average]
Of course once you have the basics sorted out one could consider fine tuning but the problem is it is very difficult to know exactly what does what. Given we were used to a much wider variety than we have now and plants are a veritable natural pharmacy (a mixture of positive and negative both of which the body can use - to support, or utilise in its armoury) variety seems a good strategy.
The China Study (about $20 US new)
http://www.thechinastudy.com/about.html
It is a very though provoking read. I have questions as to whether his conclusions would have changed in any way if he had looked at the omega three six issues. He touches on fish as a protein source but there is not much on it either way in his book. (eg Eskimos would be a fish exception to the no protein rule) The fat that goes with meat protein is clearly an issue and strict moderation likely sensible as a minimum.
I would also highly recommend Smart Fats M Schmidt (there is a newer version) which is also very thought provoking.
RB