They must do as otherwise their claims would've been taken down years ago. They did proper scientific studies to prove that it does.
That's a pretty reasonable way to think about it (and how it should be), but sadly scientific studies aren't as pure as everyone thinks they are.
The amount of utter nutritional tripe that is widely peddled on just about medium is pretty staggering. It's actually really
really hard to sift out the bad and biased advice from the good stuff.
The post above me is a good example. It's got some truth to it, but then there's the video. If you watch the video, it sounds reasonable, quotes a study or two for authority, so seems legit. A lot of what the video says might contradict what your GP would tell you, which doesn't necessarily mean it's wrong, but then when you check out the author of the video you see he's homeopathy/acupuncturist salesman. I've got no idea what the video goes on to talk about as I only watched the first couple of minutes, but you can instantly see the video's motives.
I'd strongly recommend anyone with even a slight interest in the topic to have a look at some of the stuff done by guys like Ben Goldacre. He's got a book out called 'Bad Science' which is a fascinating read. There are also a bunch of good videos of him talking on YouTube.
Not strictly relevant to Benecol, as I've got no idea about it. I guess one spread is as good as another in moderation.