If you think that you might have an issue get blood testing. Afterwards you know if you lack some nutrient that the test investigates.
I recommend privatemdlabs. Much cheaper for many people than going through the song and dance of getting a referral from a GP and then wheedling the raw results out of them (GP's don't like to share info IME).
This is a thread where people can ask questions that they would ordinarily feel embarrassed for not knowing the answer to. The previous "stupid" questions thread is at almost 500 questions in about a month, so I think it's time for a new one.
Also, I have a new "stupid" question.