The decrease in osmotic fragility of erythrocytes during supplementation with n-3 fatty acids is a transient phenomenon.
In order to study the effect of dietary n-3 fatty acids on osmotic fragility of human erythrocytes, 11 healthy subjects were given a supplement of 6 g day-1 of an oil containing 50% n-3 fatty acids for either 14 days or 34 days. Fourteen days after start the osmotic fragility was decreased by 60-80% (buffer-salt concentration 0.41%), and the level of n-3 fatty acids in membrane phospholipids was increased by approximately 60%. The decrease in fragility was less marked after 24 days and almost at the pre-supplementation level after 34 days. There was no correlation between changes in fragility and in the fatty acid pattern of membrane phospholipids of the erythrocytes. The changes induced in fatty acid composition of phospholipids did not affect membrane fluidity. It is concluded that factors other than the nature of fatty acids in membranes may be involved in modifying osmotic fragility, and that there is no correlation between membrane fragility and membrane fluidity.