[bluGill]

Nutrition studies come in two forms: these results apply to those confined to a hospital bed (or prison cell) and probably do not generalize to the normal population ; and despite our best efforts we were unable to get the subjects to adhere to their assigned diet.

Things aren't quite that bad, but it is close.

It doesn't help that many people have a bias and look for ways to bias their study. Studies that don't control for smoking find vegetarian diets are a lot healthier than those that do.