URINARY MALONDIALDEHYDE-EQUIVALENTS DURING INGESTION OF MEAT COOKED AT HIGH OR LOW-TEMPERATURES

Excretion of malondialdehyde (MDA)-generating substances in the urine has been suggested as an indicator of in vivo lipid peroxidation. Howe ver, MDA in the urine also reflects the amount of lipid peroxidation p roducts consumed in the diet. We determined MDA as the thiobarbituric acid (TBA)-MDA complex in urine of 19 healthy adults (10 male and 9 fe male) fed large quantities (3.6-4.1 g/kg body weight) of ground beef c ooked at a low or a high temperature. Subjects ate a controlled diet w ith no alcohol or nutritional supplements. For 7 d they consumed groun d beef cooked at 100 degrees C for 20 min (low-temperature meat) follo wed by 7 d with meat fried at 250 degrees C for 22 min (high-temperatu re meat). Prior to the study, subjects consumed their normal free choi ce diet with moderate amounts of meat. The concentration of MDA in uri ne at baseline was 2.1 +/- 0.3 mu mol TBA-MDA equivalents/day (mean +/ - SEM). After 7 d of low-temperature meat, urinary TBA-MDA equivalents increased to 23.1 +/- 1.4 mu mol/d. Urinary TBA-MDA equivalents were consistently lower (6.9-8.0 mu mol/d) 1, 2, 3, and 7 d after subjects changed to high-temperature meat. After 7 d of treatment, 97% of the M DA-equivalents in the meat was recovered in 24-h urine samples. The lo w temperature meat had 3-4 times more MDA than did the high-temperatur e meat. These data indicate that the amount of meat eaten and the cook ing procedures used can dramatically alter urinary MDA. Dietary source s of MDA must be controlled if urinary MDA is to be used as an indicat or of oxidative stress.