Agree. I can see two reasons for this. One is that all humans are biochemically unique. A diet that works well for one person won't necessarily work well for another.
The other reason is the food industry financing "research". For example, sugar companies financing studies that tell you that artificial sweeteners are unhealthy.
Actually, there seems to be one more reason. Cultural "taboos". For example, lots of people will tell you that eating too much sugar, fat, salt etc. are bad, BUT you never hear that eating too much protein is bad, even though there is research that shows this. Seems like there's some sort of taboo against saying anything bad about protein.
Also "fat <> fat" ... I eat every day at least one tablespoon of linseed oil. And that is very good for me and my brain :)
Furthermore, I personally guarantee your flax oil is rancid. That shit does not keep. Eat sardines.