Generally, I leave it to food scientists - or at least cooks of a scientific bent - to debunk received cooking wisdom that isn't actually all that wise. For instance, it turns out that searing meat doesn't seal in the juices at all, and merely (merely!?) makes the meat taste better. But sometimes, observant cooks can figure out for themselves that, for example, the green core of a germinating garlic clove does not taste bitter, as so many cookbook writers say it does, presumably not having tasted before they wrote.
And other times, it takes a lazy cook, like me, to amble down the easier path and thereby discover that what he'd been taught just isn't so. Beets, I was always told, will bleed like stuck pigs if peeled before being cooked, losing much of their flavorful juice in the process. But it is easier to peel them raw than cooked (again, not what we're told), so I did that today before arranging them on a glass dish, covering them with plastic wrap (pierced) and microwaving them until they were done. No, I won't give a timing: it depends on the beets, on how many you're cooking and on how tender you want them. Check them every three minutes, then when they get close to doneness every minute.
Here is what my beets looked like when they were done.
The amount of juice they emitted was about the same as unpeeled beets cooked the same way. So much for that myth - at least when microwaving is the method of choice: oven-roasting wrapped in foil might yield a completely different result for all I know. I'll try it next time the oven is on.