1996 AOCS Meeting, Indianapolis
Session: Biological Analysis of Essential
Fatty Acids (EFAs).
Objective: to discuss analytical methods to measure fatty acids, particularly EFAs, in biological tissue.
How do we determine who needs EFAs? What are the methodological issues involved in designing clinical trials for food supplements and measuring EFA status? How do we relate EFA abnormalities to food supplements? Why should one measure EFAs? Are there key "faults" in published studies that impact nutritional recommendations for fat? How do errors in EFA measurement translate into misconceptions about nutritional effects of saturated, monounsaturated and polyunsaturated fatty acids?
Topics include (emphasis on
analytical methods):
Measurement
of very long chain PUFAs such as 20:4w6, EPA and DHA. Where they are found. How
they can be detected.
Columns used
to measure fatty acids. Pros and cons. Which ones can detect 20:3w9, 16:1w7,
the EFAs and their derivatives. Comparison from different manufacturers.
Problems in measurement of small peaks in biological tissues.
Instrumentation
to measure fatty acids. Recent changes in GLC. Flow control. Improvements vs
regular GLC. Compare the same sample with the same column in an older vs newer
GLC model. Other analytical issues in instrumentation and how they improve the
measurement of PUFAs.
Measurement
of unusual peaks in foods and in biological tissues. There are many peaks in
plasma and human tissue. What do they tell us about dietary food? What are the
analytical problems involved in measuring those peaks? How can we use them to
evaluate the nutritional effects of new or designer foods?
Integration
of peaks. Deconvolution. Advances in computer software to identify and
integrate peaks. Comparison of various software programs in their ability to
separate peaks and automatically integrate and identify them.
Chemical
extraction of EFAs in biological tissues. Instrumentation, automation, errors.
Quality control in processing many samples.
Diagnosis of
EFA abnormalities: analytical methods. Clinical nutrition. Designing optimal
foods. Implications for instrument and food manufacturers.
Problems and Issues in the
Diagnosis of Essential Fatty Acid Deficiency in Biological Tissues. Overview.
Edward Siguel, Boston, MA.
Key Words: Essential Fatty Acids, biological tissues, methods,
measurement, implications.
Designing optimal foods. Implications for instrument and food manufacturers.
Evaluation of essential (EFA) and polyunsaturated fatty acid (PUFA) status in biological tissues involves 4 major steps: (a) extraction and preparation of fatty acids (usually methylation) for analysis (5-10 hours); (b) separation by capillary column gas liquid chromatography (30'-180'); (c) peak integration and compound quantification (5'-60'); (d) evaluation of fatty acid profile (5'-120').
Using biological tissues, researchers diagnosed w6 EFA deficiency (EFAD) by the ratio of 20:3w9/20:4w6 (triene:tetraene or T/T ratio) > 0.2. Modern columns (100m) allow clear separation of 20:3w9 from other peaks. New normal "reference" levels are T/T < 0.02 in whole human plasma.
In human blood, w6 > 5w3. Thus, small changes in w3 rarely modify T/T ratios and different measures are needed for w3 deficiency. The technical problems involved in accurately measuring very low T/T ratios and other markers of fatty acid abnormalities include baseline noise, random and contamination peaks; poor peak separation (resolution), shifts in column efficiency; integration and peak identification errors; interpretation of percents and concentrations of fatty acid compounds. Common errors in published reports include peak superimposition, incorrect peak identification, and integration errors.
PUFA compounds other than arachidonic and linoleic acid are usually below 2% of total fatty acids. Linolenic, EPA, GLA are usually under 1%. For these peaks, quantitation errors can be greater than 100%, a combination of peak superimposition and integration errors. Incorrect peak identification is also common with short columns or short methods. Short methods may separate 100 peaks vs. 400+ found with a long column and method. Applications to the diagnosis of insufficient levels of fatty acids and other fatty acid abnormalities are presented.
We will discuss implications for the design of foods and the interpretation of scientific publications that form the basis for policy making.
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Organizations interested in analyzing samples for fatty acid composition may contact us. |
Comparison of Capillary Columns for the Analysis of Fatty Acids in Biological
Tissues.
Leonard M. Sidisky and Kathleen H. Kiefer. SUPELCO, Inc., PA.
Key Words: Fatty acids, methods, measurement, columns.
Salmon: A preferred source of
DHA in human nutrition.
(reviewing analytical methods for lipid recovery, fatty acids, etc). See abstract.
Dr. R.G. Ackman, Canadian Institute of Fisheries Technology, Halifax, Nova Scotia, Canada.
Key Words: Fatty Acids, sources, methods, measurement, implications.
Essential Fatty Acids in
Adrenoleukodrystrophy and other Peroxisomal Disorders.
Dr. Ann B. Moser, Kennedy Krieger Institute, Baltimore, MD.
Key Words: Essential Fatty Acids, neurological tissues, methods, measurement, implications.
Challenges Associated with Fatty
Acid Analysis of Blood Samples from Large Scale Clinical Trials.
Nancy L Morse, EFAMOL Research Inc., Kentville, NS, Canada.
Key Words: Essential Fatty Acids, large scale methods, measurement.
Optimization of FAME analysis
through the use of Electronic Pneumatic Control.
Dr. Albert E. Gudat and E. Siguel
Key Words: Fatty acids, methods, GLC, instrumentation.
Panel Discussion. Implications
for the food industry. Implications for clinical trials and studies on the
effects of fats. Implications for nutrition, medical care, nutrition recommendations.
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© 1998 Edward Siguel. All rights reserved |
modified 9/14/98 |