Skin flushing, gastrointestinal upset, and itching may be caused by therapeutic doses of:
a. pyridoxine.
b. niacin.
c. vitamin C.
d. thiamin.
Question 2
The amino acid that is a precursor to niacin is:
a. leucine.
b. phenylalanine.
c. tryptophan.
d. valine.