Some peo­ple argue that sug­ar should be reg­u­lat­ed, like alco­hol and tobac­co, on the grounds that it’s addic­tive and tox­ic. How much sense does that make? We hear from a reg­u­la­to­ry advo­cate, an evi­dence-based skep­tic, a for­mer F.D.A. com­mis­sion­er — and the orga­niz­ers of Milktoberfest.