A meta-analysis to assess the effect of the composition of dietary fat on α-tocopherol blood and tissue concentration in pigs.

A meta-analysis based on the results from 13 selected publications was performed to assess the effect of dietary fat supplementation (quantity and fatty acid composition) on α-tocopherol (TOL) concentration in 4 pig tissues (blood, liver, muscle, and adipose tissue). Dietary fat supplementation was defined by the quantity of fat added to the basal diet and its fatty acid profile. After standardization of tissue TOL concentration (as the dependent variable), statistical analyses were performed using multiple nonlinear regression, data partitioning, and partial least squares regression with 7 predictor variables including added vitamin E (VE), added fat, PUFA (% fat), MUFA (% fat), SFA (% fat), omega-3 fatty acids (-3; % fat), and omega-6 fatty acids (-6; % fat). The statistical analyses first showed that the VE level in the diet was the main factor that modulates tissue TOL concentration. The dose-response relationship followed a logarithmic curve, with a saturation of tissue TOL concentration in all the studied tissues. Moreover, the amount of dietary fat, at least up to 20%, was not linearly correlated with tissue TOL concentration, considering that the main fatty acid classes, MUFA and, to a lesser extent, SFA, were positively associated with tissue TOL concentrations. Finally, this study suggests that the inclusion of -3 fatty acids in the diet may decrease tissue and, more precisely, blood TOL concentration.