This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables.
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 variety of officially recognized forms of vitamin E listed in the National Formulary: α-D or α-dextrolevo (DL) tocopherol, α-D or α-DL tocopheryl acetate, α-D or α-DL tocopheryl acid succinate, mixed tocopheryls concentrate, and α-D tocopheryl acetate concentrate. The concentrates are obtained from edible vegetable oils or from the by-products of their refining. The National Formulary (NF XIII) establishes appropriate standards of purity for each and requires vitamin E products to be labeled in terms of international units as
Alperin G. Natural vs Synthetic Vitamin E. JAMA. 1973;226(6):672. doi:10.1001/jama.1973.03230060048020