I find it irrelevant personally. I mean you can do controlled experiments in chemistry or physics and get quite useful results. There what's in vitro is kind of the point. But with something as complex as human behaviour (which is why sociology is questionably scientific) or even human diet ...
An "experiment" in that kind of context doesn't seem to mean much more than putting some limited secondary assumption, that may not be particularly relevant, to the test. Take too much notice of these, as the media does, and you could be chasing down one rat hole after another, adjusting your diet in accordance with the results of an experiment which was actually pretty much beside the point as they'd never even thought to question an assumption further back up the chain of assumptions. It's all interesting for research purposes; it could be downright misleading for practical decisions about how to live here and now. I just don't see how it could be more helpful than the "historical" perspective. If myocardial infarction was rare as recently as the 1930s, at a time when people were eating more saturated fat, how can eating saturated fat be its cause? Likewise if known populations, such as the Eskimo and the Maasai, ate diets even higher in saturated fat, but didn't die from this cause, something seems to be up with the assumption.
People here have linked a blog by a Stephan Guyenet before. He's apparently a neurobiologist. Anyway, he does offer discussions of various studies on the lipid hypothesis. Here's an example:
Now that we've seen that the first half of the diet-heart hypothesis-- that dietary saturated fat and cholesterol elevate serum cholesterol and low-density lipoprotein (LDL)-- is false, let's take a look at the second half. This is the idea that elevated serum cholesterol causes cardiovascular disease, also called the "lipid hypothesis". ...</blockquote>