If the chromic acid oxidation is performed with stoichiometric oxidant in the presence of diethyl ether as co-solvent (a method introduced by H.C. Brown), the epimerization of l-menthone to d-isomenthone is largely avoided.
Apple cider vinegar isn't likely to be effective for weight loss. Proponents of the apple cider vinegar diet claim that drinking a small amount of apple cider vinegar before meals or taking an apple cider vinegar supplement helps curb appetite and burn fat. However, there's little scientific support for these claims.
In the 1970s, apple cider vinegar became popular once again, this time with the help of proponents who had read Jarvis' book and suggested that apple cider vinegar (along with kelp, vitamin B6, and lecithin) could help people lose weight by speeding metabolism and burning fat at a faster rate.