If you are not aware of the work of Weston Price into nutrition and the effects of following the dangerous path we currently walk as a society you should be! His book is available from the Price-Pottenger Nutrition Foundation.
As for Vitamin D, try eating shrimp (and other sea foods) and the organ meats of animals (liver, kidney, etc. which were all commonly eaten in the recent past). These are the best sources, and they are available all year round.
The links between criminality and nutrition are absolutely fascinating. Things are not as they are meant to be. Things we call food are often no such thing.