It is correct as "se debe." This is an example of the impersonal "se," which is always used with a third person singular verb. [más fruta y verdura] is the direct object. There is no agreement in Spanish of the verb with the direct object.

Hi Teryl, This is a good question. The answer is not straightforward. I hope you can read through this explanation: https://www.fundeu.es/recomendacion/se-puede-se-pueden/ For your sentence, the preferred option is to use the plural: Se deben comer más frutas y verduras. But you could use the singular. (the options are based on whether you opt to consider "más frutas y verduras" as a subject or as the direct object of the sentence. I you rearranged the sentence though, the plural would be a must: Las frutas y verduras se deben comer al natural (your original sentence would be valid but strange if rearranged). Saludos, Antonio

going deeper into these sentences i found them a bit incorrect actually, to start with if u say "se debe comer mas fruta y verdura" u cant write verduras in the plural form, if u do so then u would have to write "se deben comer mas frutas y verduras". So these are the options, "se debe comer mas fruta y verdura" or "se deben comer mas frutas y verduras". Hope that helps, let me know if it is still not clear for u. Btw, srry if i didnt use apostrophes, my keyboard isnt working as it should be xD.

Hola Teryl En este caso, no hay problema si solo utilizas "se debe", hay personas que también utilizan "se deben" pero lo más correcto es la primera opción. ¡Saludos!