Diet CAN affect what cholesterol is bound to in the bloodstream, and thus whether it will travel as LDL, HDL, VLDL, etc. Free cholesterol is not soluble in water, so in order to travel in the bloodstream it has to be complexed to something. In LDL cholesterol, for example, Some cholesterol is chemically bound to fatty acids (esterified). This cholesterol-ester is in the hydrophobic (can't dissolve in water) core of LDL. This is surrounded by a polar lipid layer that includes non-esterified cholesterol. Added to this is a protein (ApoB) that directs LDL to the LDL receptor.
There can be some variability in the cholesterol content in LDL particles, and this may be affected by diet. There is a reverse relationship between triglyceride levels and LDL particle size, but recently it has been purported that the absolute number of LDL particles (LDL-P) is a more important marker of atherosclerosis risk than is just the LDL cholesterol level. It's a bit complicated, and definitely not entirely worked out, but yes, diet can affect your lipid profile as well as your lipid levels.
Regarding your question about statins and survivability, yes, there are studies that demonstrate this. The original 4S study is one. This demonstrated a 30% reduction in mortality in the statin group. There are many other studies that show survival benefit, but not all studies demonstrate this. That said, the vast majority demonstrate significant decreases in cardiovascular events and stroke. Survival can be affected by many non-cholesterol related factors, and even bypass surgery and PCI/stenting do not prolong life in most circumstances. It's about quality of life, and if you can avoid an MI or stroke your quality of life is very likely to be better than if you didn't avoid them.
Finally, our bodies make about 1 gram of cholesterol per day. American dietary intake is estimated on average to be ~500 milligrams per day, half what we make. There are studies that demonstrate a reduction in endogenous cholesterol synthesis in response to increased dietary cholesterol intake. The significance of this, and whether or not it effects synthesis in all cell types is not, to my knowledge, defined. Also, any such study would have to also study the fate of cholesterol in the context of dietary alterations in synthesis (e.g. what does this do to bile acid synthesis, neurosteroid synthesis, etc.).
My general approach is to not jump to conclusions, read the data, keep an open mind, and to not put too much credence on those who purport to know more than everyone else - and who are profiting by this position.
Thanks! Great answer.
It is not a question of putting credence in any human. If I am being asked to just “believe” somebody including my own doctor, well I may need to do that, but I still do my own reading. Here on FR the ad hominem attack is not generally considered to be a fallacy!
FReegards.