By THÉRÈSE MARGOLIS     Most of us who grew up before the advent of GNC Ultra-Mega Extra-Charged Cuadruple-Action Multivitamins (we had plain old One a Days) and Grass Green Vegan Organic Superfood Capsules (our moms just gave us an apple a day and sent us out to play), remember – less than fondly – that dreaded brown bottle of cod liver