Food Lipids: Chemistry, Nutrition, and Biotechnology

17
Fats and Oils in Human Health
DAVID KRITCHEVSKY
The Wistar Institute, Philadelphia, Pennsylvania
I. FATS AND OILS IN HUMAN HEALTH
Most discussions of fats and health focus on the deleterious effects of these essential
nutrients. What we are really discussing in that case is the possibly harmful effects
of an excess of fats and oils. Fats (lipids) supply energy, support structural aspects
of the body, and provide substances that regulate physiological processes.
Adipose tissue, which is the repository of most of our body fats, serves as an
energy reservoir (fat supplies nine calories per gram compared to four calories per
gram for protein or carbohydrate), as a heat conserver and as a shock absorber. Lipids
contain essential fatty acids, such as linoleic and linolenic acids. These are metabolized
eventually to provide eicosanoids, substances that possess hormone-like activity
and thus may regulate many body functions. Fat is also the transport vehicle
for vitamins A, D, E, and K.
Cholesterol, which has absorbed the brunt of the antifat attack, is a compound
that is essential for life. It is not essential in the sense of essential fatty acids since
the body can synthesize it, but it is a crucially important component of our biological
economy. Cholesterol comprises about 0.2% of normal body weight. Most of it
(about 33%) is in the brain and nervous system where its function has not been
probed beyond suggesting that its major function is as an insulator. Almost another
one-third of the body’s cholesterol is in muscle where it is a structural component.
Every cell membrane contains cholesterol and phospholipid, another fatty substance.
The esterified cholesterol found in muscle may represent a storage compartment. The
percentage of cholesterol ester in muscle increases with age. Cholesterol is the parent
substance for vitamin D2, bile acids, adrenocortical hormones, and sex hormones.
Thus, it is one of the more important biological substances. Fat also contributes to
the palatability and flavor of food and hence contributes to the enjoyment of eating.
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.