interesting because vitamin D is great for skin health in other ways too, and nicotine lowers surface circulation which tends to lead to clogged capillaries and poor skin condition. my primary dietary staple is milk and it's loaded with vitamin D, and my skin looks better than it has in years... and I'm managing to easily stay away from restarting the nicotine intake.
i had an unusual motivation though - severe allergies that seem to primarily come from seeds or seed fed animal products. hard to smoke when you are wheezing. plus, for me, the smoking was really just a cover for a chronic hypocapnia problem caused by seed allergy.