A survey of vitamin A concentrations in the liver of food-producing animals.
High oral doses of vitamin A have been shown to be teratogenic and accordingly the World Health Organization has recommended that the daily intake for pregnant women should not exceed 3.3 mg. Liver contains high concentrations of this vitamin and consequently it has become necessary to assess its level in the livers of food animals. A survey of fresh, frozen, imported and home-produced retail liver samples from calf (42), ox (121), lamb (228), pig (133) and chicken (125) was carried out between August 1992 and April 1993 using a modified version of the method of Ashoor and Knox (1987) to determine retinol and retinyl esters. Interlaboratory comparison showed no significant difference in results for this method and a method which employed hydrolysis of retinyl esters, and there were significant advantages in specificity, simplicity, cost and quality control. The mean +/- sd total vitamin A concentration calculated as retinol equivalents, for all species surveyed was 139 +/- 96 with a range of 3-1267 mg/kg liver. Mean values for individual species were: calf 188 +/- 125, ox 142 +/- 110, lamb 173 +/- 104, pig 174 +/- 118 and chicken 97 +/- 44 mg/kg liver. No change in the vitamin A concentrations in liver were observed compared with previous surveys in the UK, which suggests that the intake of vitamin A from dietary and supplementary sources by different species has not changed. The data from this survey confirm that liver cannot be recommended as a food for pregnant women.