Absorption of dietary beta-sitosterol in laying hens and its incorporation into the egg

Studies were undertaken to determine the dietary beta-sitosterol absorption in laying hens and its incorporation into the egg. Hens were divided into four groups and fed a commercial low-fat laying diet. Group 1 served as controls; the diet of group 2 was supplemented with 10% corn oil; group 3 with 4% plant sterols (emulsion in carboxymethylcellulose); group 4 with 10% corn oil and 4% plant sterols. The daily beta-sitosterol intake of hens in groups 1, 2, 3 and 4 was 0.036 g 0.095 g, 2 g and 2.56 g, respectively. After consuming the diets for 30 to 40 days, cholesterol and beta-sitosterol contents of the eggs were estimated by gas liquid chromatographic and mass spectrometric methods. Feeding corn oil with and without plant sterols increased cholesterol content of the eggs, while feeding plant sterols alone had no effect on egg cholesterol levels. The beta-sitosterol content of eggs from groups 1 and 2 was similar (60-66 mug/g yolk) and feeding plant sterols increased the beta-sitosterol content to a very small extent (82-90 mug/g yolk). Studies on the dietary beta-sitosterol and cholesterol absorption indicated that there was very little absorption of beta-sitosterol. In control hens, beta-sitosterol absorption was about 7% compared to 81% cholesterol absorption. Plant sterols feeding did not affect the beta-sitosterol absorption but reduced cholesterol absorption by 40%. Feeding corn oil alone did not affect cholesterol absorption. Failure to detect any significant amount of beta-sitosterol in these hens. At the peak radioactivity deposition in the eggs, only 2% of the absorbed beta-sitosterol radioactivity was found in the eggs of group 4 compared to 5% found in group 1, while cholesterol radiioactivity was nearly 4 to 5 times in both groups. These data suggested that laying hens synthesized specific lipoproteins for deposition in yolk.