Some people crave sweets and other harmful treats but that doesn't necessarily mean that your body needs it. I don't think cravings justify what your body really needs all the time. It would be hard for me to believe that most people eating a conventional SAD diet are going around craving brussel sprouts or brocolli since they don't eat it on a normal basis.
I have been craving coffee with heavy cream lately too. I just gave up coffee at the start of the New Year. I am drinking green tea but its not the same and my body is cravoing coffee with cream. But coffee with cream wrecks my digestion everytime so I know I can't have it. So in this personal case, the craving has nothing to do with what my body needs.
"If man made it, don't eat it" - Jack Lallane
People say I am on a "crazy" diet. What is so crazy about eating veggies, fruits, seafood and organ meats? Just because I don't eat whole wheat and processed food doesn't make my diet "crazy". Maybe everyone else with a SAD are the "crazy" ones for putting that junk in their system.