Food Lipids: Chemistry, Nutrition, and Biotechnology

needed trans fatty acid information to plan healthy diets were insufficient at the time
of the act’s passage. The FDA has since been inundated by petitions, nutrition studies,
dietary intake studies, and food composition data from groups and individuals on
both sides of the trans fatty acid issue.
B. Dietary Intake
There has been little agreement concerning the ideal level of trans fatty acid consumption.
One estimate indicated that daily trans consumption could be as high as
38.6 g in some individuals, with an average consumption of about 13 g/day [148].
Subsequent reports, however, suggest that these estimates may have been based on
‘‘questionable composition and consumption data,’’ with the result that the average
consumption of trans fatty acids in the U.S. diet may instead be closer to 8 g per
person per day [149,150]. The International Life Sciences Institute report [4] cited
at the beginning of the chapter summarized consumption data from several studies
and found the average daily consumption to range from 2.7 to 12.8 g of trans fatty
acids per day. The four studies that differentiated between animal/dairy and vegetable
oil sources of trans reported that 78–92% of the trans fat came from vegetable oil
sources.
C. trans Content of Food Products
An indicated by the intake data, the main source of fatty acid isomers, including
trans fatty acids in the U.S. diet, is the partially hydrogenated vegetable oil used to
make margarine and shortening. The positional isomer distribution of the double
bonds of trans-octadecenoic acids reported for Canadian margarines ranged from the
n-4 to the n-14 position, with most of the isomers at the n-8, n-9, and n-10 positions
[151]. It is interesting that different brands of margarine made from the same oil raw
materials had significantly different double-bond patterns.
An analysis of over 90 U.S. commercial margarine products in 1985 found that
the total amount of trans isomers varied between about 10 and 30% [152]. The trans
positional isomers were fairly evenly distributed throughout the fatty acid chain,
whereas the cis positional isomers were concentrated at the n-9 and n-10 positions.
The diene content of the margarines varied greatly, and all dienes were reported to
be 9,12-18:2 isomers [152]. A survey of 197 food products in Germany [153] found
the following levels of trans fatty acids:
Milk and milk products, 1.9–7.9%
Meat from ruminants, 2–10.6%
Pork fat, less than 0.5%
Foods that may contain hydrogenated oils, 0–34.9%
A 1996 capillary GC survey of 18 food products in the United States found that the
level of trans relative to the total fat content varied from 1.5% for ‘‘fat-free’’ margarine
to 42.9% for chicken-flavored crackers [32].
If, as reported, the level of trans fatty acids in food products has indeed decreased
in the last several years, this result is most likely due to improved processing
as well as the adverse publicity trans fatty acids have received. For example, a
French study reported a decrease of trans monoenes in tub margarines from 13% of
the total fat in 1991 to 3.8% in 1995 [154]. However, the study also reported trans
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.