TRANS-18 1 ACID CONTENT AND PROFILE IN HUMAN-MILK LIPIDS - CRITICAL SURVEY OF DATA IN CONNECTION WITH ANALYTICAL METHODS/

This study presents an in-depth, critical survey of the current knowle dge about trans-18:1 acid content and profile in human milk lipids. Em phasis is placed on the analytical methods employed to quantitate tran s-18:1 acids, most of which lead to imprecise quantitative data. It is demonstrated that data obtained by single gas-liquid chromatography ( GLC) on polar capillary columns are underestimates by 25-40%. Several experiments indicate that the total content of trans-18:1 acids in hum an milk is directly related to the quantities ingested the previous da y(s), provided no gross weight loss occurs during breast-milk feeding. Equations have been proposed to describe this relationship, and appar ently the percentage of trans-18:1 isomers, relative to total fatty ac ids, is approximately three-fourths the quantity (in g) ingested by la ctating mothers. That is, the determination of the trans-18:1 acid per centage in human milk is a convenient means to estimate trans-18:1 aci d consumption by corresponding populations. Adapted methods (i.e., sil ver-ion thin-layer chromatography, coupled with GLC on long polar capi llary columns) allow accurate quantitation of most individual trans-18 :1 acids, more particularly of the trans-Delta 16 isomer. This determi nation, along with a knowledge of the distribution of individual isome rs in ruminant fats and partially hydrogenated oils, is a convenient m eans to estimate the relative contribution of these two dietary source s to the distribution of individual trans-18:1 isomers in human milk l ipids. A comparison of human milk and infant formulas is made with reg ard to trans-18:1 acid content and profile. Important differences are noted between data from European countries and from North America.