The form helta- in the Etymologies is a misreading according to VT/46:14
Noldorin
mann
noun. food
aes
noun. cooked food, meat
cam
noun. hand
cam
noun. hand
camb
noun. hand
camm
noun. hand
camm
noun. hand
heltha-
verb. to strip
mad-
verb. to eat
mân
noun. departed spirit
mō
noun. hand
ON. hand
othlon
noun. paved way
othlond
noun. paved way
rada-
verb. to make a way, find a way
The earliest word for “food” in precursors to the Sindarin language was G. môs “food (of men)” (GL/56, 58), probably based on the early root ᴱ√M(B)ASA “cook, bake” (QL/59). This became ᴱN. math “food” in Early Noldorin Word-lists of the 1920s, appearing only in its lenited form vath as an element in ᴱN. orvath “foodless” (PE13/155). In The Etymologies of the 1930s Tolkien had N. mann “food” as a derivative of primitive ᴹ✶matna under the root ᴹ√MAT “eat”, but the version of the entry where this form appeared was struck out (EtyAC/MAT). The primitive form ✶matnā “food” did reappear in the early 1950s, however (PE22/136).
Neo-Sindarin: Of the above, I prefer ᴺS. math for “food”. I first saw math proposed as the Neo-Sindarin word for “food” in a list of neologisms by Elaran on the Vinyë Lambengolmor Discord Server (VLDS) from 2018. I prefer math because I tend to assume Q. matta is derived from ✱mattā rather than ✶matnā to avoid certain phonological difficulties; see that entry for discussion. If you are not concerned with those difficulties, ᴺS. mann “food” is also viable.