Content of phospholipids in human diets studied by the duplicate-portion technique

Abstract

1. The phospholipid intake by eight healthy women was studied by the duplicate-portion technique, i.e. chemical analyses of duplicates of the food consumed. Their intake of phospholipids was 1.5-2.5 mmol lipid-phosphorus/d, which corresponds to 0.0234059 mmol lipid-P/g dietary fat and 0.240.45 mmol lipid-P/MJ respectively.2. Choline phosphoglyceride constituted 48&700 mmol/mol and ethanolamine phosphogl yceride 170-240 mmol/mol total lipid-P. Most of the choline in nature occurs as choline phospholipids, the intake of which ranged between 0.91-1.85 mmol/d or 0.154.33 mmol/MJ.3. Palmitate, stearate, oleate, and linoleate were the four major fatty acids both in choline phosphoglycende and ethanolamine phosphoglyceride. Significant amounts of highly unsaturated, C,, and C,, fatty acids were also observed. It was calculated that 13-33 mg/g total dietary fatty acids was consumed as phospholipids. Together with bile phospholipids, dietary phospholipids and their degradation products may be important in the digestion and absorption processes. The intake of phospholipids by healthy free-living subjects has been studied. This study was part of a project designed to assess dietary intake by chemical analysis of so-called duplicate portions (Borgstrom et al. 1975;Borgstrom et al. 1979). This methodological approach is especially advantageous for components which are not listed in customary food composition tables, such as polar lipids. E X P E R I M E N T A LThe subjects studied were eight healthy women, aged 34-69 years, who formed part of a reference group in a study on dietary intake in relation to blood pressure. Other aspects of their dietary intake are reported elsewhere (Thulin et al. 1980). The nutrient intake agreed well with the pattern normally encountered in Sweden. Each subject collected six daily portions as described previously (Thulin et al. 1980). The portions were homogenized as described previously (Borgstrom el al. 1975) and 2-5 g of the homogenate was extracted for 1 h with 5 vol. chloroform-methanol (1 :2, v/v). The mixture was filtered and the extraction was repeated with 3 vol. chloroform-methanol(1: I , v/v). Enough water to give a value for water-methanol of 1 : 1 was added to the combined extracts and the chloroform layer was recovered after phase separation. After drying and weighing, total lipids were dissolved in chloroform and separated into a neutral lipid fraction and a polar fraction by column chromatography on silicic acid (< 200 mesh; Mallinckrodt). The first eluent was chloroform (20 ml/g silicic acid) and the second eluent chloroform-methanol (1 : 1, v/v) plus methanol (each 7-10 ml/g silicic acid). The phosphorus content in the polar fraction was determined according to Chen et al. (1956). Phospholipids were separated by thin-layer chromatography on silica gel H with chloroform-methanol-acetic acid-water (65: 25 :4:4, v/v) as the developing solvent. The phospholipid fractions were either eluted with chloroform-methanol-acetic acid-water (50: 39: 1 : 10, v/v) (Akesson et al. 1970) or ...

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