Actually, what worked for your husband is a significant change in diet and lifestyle, and vit C may or may not be the thing that fixed the problem.
Regular exercise, elimination of Sugar and milk from diet are very often more than enough to improve health to a such level, that all bad Body Odor disappears!
But, it is also possible that without extra vit C it would have taken significantly longer time ...
It is also possible that if he was just taking the vitamin C, without making changes in his diet and lifestyle, it is still possible it would worked and it could help him with his Body Odor , but it may very well be that diet and lifestyle changes were needed together with vit C to achieve the same results ...