Not if they put "multiple sclerosis" into the search engine, no. Only if they put "MS".
These are both bad domain-names, in my opinion, neither of which I'd consider buying.
I appreciate that this is only an example, not your real keywords, but see if this helps: if "multiple sclerosis" and/or "diet" and/or "multiple sclerosis diet" are the keywords for which you want to rank, but you can't buy those exact domain-names because they're already registered, you should be looking for any additional letters/words you're adding to go after the keywords, not before.
"The new" at the start of the domain-name is not so good.
multiplesclerosisdietxyz.com is more promising than thenewmultiplesclerosisdiet.com