Because of the importance of osteoporosis, the area of vitamin D research has
become exceptionally active in the generally quiescent vitamin field. Vitamin D analogs
such as calcitriol (8.58,1α,25,25-trihydroxycholecalciferol) and other compounds have
been suggested as new drugs for these conditions.
8.2.8.11 Vitamin E (Tocopherol)
Vitamin E (8.59, tocopherol), a chromane, occurs in just about all vegetables as well as
in oils, grain, milk, meat, and yeast. Its principal known action is the maintenance of
normal pregnancy in rats kept on a special diet. Vitamin E-deficient rats reabsorb their
fetuses even though they are developing normally in every other respect. There is no
evidence for this in humans. The vitamin has antioxidant properties, probably stabiliz-
ing vitamin A and unsaturated fatty acids and preventing free-radical reactions. Free
radicals, according to some hypotheses, may be involved in aging. Accordingly, some
researchers have advocated the ingestion of large doses of vitamin E (2000 IU/day) for
the treatment of Alzheimer’s disease. However, large doses such as this (especially
when co-administered with an anti-inflammatory agent such as acetylsalicylic acid)
may predispose to bleeding problems. Vitamin E deficiency is unknown in humans, but
there are periodic fads promoting the intake of vitamin E.
8.2.8.12 Vitamin K 1
Vitamin K 1 (8.60) is a phytyl-naphthoquinone occurring in the green leaves of most
plants. The several related active compounds differ in the length of the phytyl side chain.
ENDOGENOUS MACROMOLECULES 511