Influence of casein versus soy protein isolate on lipid metabolism of minipigs

This report describes whether a complete exchange of soy protein isolate for casein affects serum lipid or lipoprotein levels. For this purpose, 10 adult minipigs underwent two 6-week crossover experiments, one with 11 and one with 22 weight % protein in a western-style diet. Cholesterol levels were 2.02 +/- 0.06 and 1.98 +/- 0.04 mmol/l with casein and soy, respectively (22 weight %) and 2.08 +/- 0.06 and 2.04 +/- 0.05 mmol/l, respectively (11 weight %). There was a significant rise of high-density lipoprotein cholesterol by the lower protein intake, both with casein and soy. In all experiments nitrogen balance was positive. Soy feeding was accompanied by a significant rise of fecal bacterial protein excretion, as calculated from diaminopimelic acid. In summary, no statistically significant difference of plasma or low-density lipoprotein cholesterol levels were observed, neither due to the kind nor to the amount of dietary protein.