Natural vs Synthetic Vitamin E
To the Editor.—
Dr. Ayers questioned (225:1124, 1973) Nagy's reply to the question of natural vs synthetic vitamins as being biologically equivalent. He referred to the difference in optical rotation of vitamin E derived from natural vs synthetic sources and their difference in potency on a milligram-for-milligram basis.
Many substances that are identical chemically except for optical activity (dextro [d] vs levo  form) are not biologically equivalent. Further, there are a...