Food and Vegetables have vitamins in them.
Retinoic acid is a noun for a derivative of vitamin A. That is the definition and it's also a sentence for retinoic.
The more polyunsaturated fats you eat, the more vitamin E you will get.
I eat a vitamin every day before school.
You need your vitamin c
No. It's not necessary. Capitalize it only when it forms part ot the proper noun. Example: Vitamin Shop Store
He supplements his income by working nights. (verb) They take vitamin supplements. (noun) Pregnant and nursing mothers should usually take an iodine supplement. (noun)
Vitamin A.
Vitamin A
No, the word "vitamin" should not be capitalized unless it is the first word in a sentence or part of a proper noun (e.g. Vitamin C).
Vitamin toxicity can be prevented by minimizing the use of vitamin supplements.
My Mum supplements her diet with vitamin pills.
You can, but traditionally coordinating conjunctions (such as and, but, or) are not used to start a sentence. You might consider using "alternatively" instead. For more synonyms of "or" consult a thesaurus or dictionary.