I used to peel carrots, but not any more, ever since I discovered that the nutrition lies in the skin. Now I know that vegetable waste - such as onion and garlic skins, citrus peels and, of course, potato skins - is also rich in nutrients, so I do not throw it away.
The reality is, as with most fruits and vegetables, the skin holds more nutrients and fibre than the vegetable itself.
I also no longer throw away the bottoms of a bunch of celery; instead, I cut off a portion at the bottom, separate the short stalks to wash off the dirt that lies in between, and juice the stalks or throw them into the stock pot.
I also throw onion and garlic skins into the stock pot. Not only do they add flavour, but they also add nutrients and, yes, a rich colour to the stock. Onion skin, for one thing, actually has more antioxidants than the onion itself.
Vegetable tops and lemon peels are also useful.
When I make stock with prawn shells - by dry-roasting them in a wok, then adding water to boil - I stir-fry the green tops of leeks and throw them into the pot. As for lemon peel, I use it in many ways - to make lemon-flavoured olive oil, lemon pepper or even to infuse my bottle of gin.