EFFECT OF DIETARY MACRONUTRIENT CONTENT ON CARNITINE EXCRETION AND EFFICIENCY OF CARNITINE REABSORPTION

We examined the effect of macronutrient content on glomerular filtrati on rate (GFR), and excretion, reabsorption, and filtered load of carni tine. Ten subjects consumed five diets [high protein (HP), low protein (LP), control, high fat (HF), and high carbohydrate (HC)] of equal en ergy and carnitine content for 6 d each, in a randomized crossover man ner. The rate of carnitine excretion was lower after the LP diet than after the HP diet because of lower GFR after the LP diet. The rate of carnitine reabsorption was lower after the LP diet than after the HP d iet, also because of the lower GFR after the LP diet. The rate of carn itine reabsorption was not different after the HF and HC diets, nor wa s GFR. The filtered load of carnitine, however, was greater after the HF diet, resulting in a higher rate of carnitine excretion.