You mentioned that some vitamins may cause hair loss. Could you elaborate on that?
Essentially, overdosing anything that may be good taken in low quantities, can cause hair loss when taken in high quantities. In my brief review of the subject, the data is not clearly defined. There is a worthwhile site for answers to your question, written by Dr. Michael Biamonte, found here.
Summarizing what he said: We know that toxic levels of minerals such as lead, cadmium, mercury, iron, aluminum and copper commonly cause hair loss. Copper also prevents zinc from its effectivness at preventing hair loss.
Zinc, iron, B vitamins, essential fatty acids, amino acids and other nutrients are responsible for hair growth. If deficiencies occur, for whatever reason, hair loss is likely. Poor diet or malnutrition also can contribute to hair loss as the body will shut down hair growth to save nutrients for other ‘more important’ functions.