In 12 of the 32 participants (six men aged 47-76 and six women aged 36-84), the lowest eGFR in the postprandial period fell into a worse category than the preprandial eGFR. In 11 subjects, CKD staging declined to stage 3 from either stage 1 or 2 or normal renal function. In these subjects, eGFR declined from 67-97 mL/min per 1.73 m2 pre-prandially to below 60 mL/min per 1.73 m2 postprandially.
Further research is needed to determine the impact of different meat loads on serum Cr. Creatine found in muscle is converted to creatinine when heated or cooked. The creatinine content of a meat depends on its content of muscle compared to protein (Food Chem. 1998;63:187-190). It should not be surprising that hot dogs, with their relatively high fat content, have less creatine and creatinine per gram than cooked ham. Most lunches eaten by the subjects in Dr. Preiss’ study contained beef, but two meals had chicken and three had lamb. Future research also needs to include fish, as nothing is known about its creatinine-raising potential.
More studies are needed to determine how long the elevation of serum Cr persists after a meat-containing meal. Since Preiss’ group observed little decrease between one to four hours postprandially, it is likely that a fasting serum sample of at least eight hours will be needed to minimize the influence of recent meat consumption on serum Cr. An alternative would be to advise the patient not to consume any meat on the day of testing so that the last possible meat consumption would be the evening before.
Using one of these precautions would be especially important when diagnosing CKD stage because misdiagnosis may lead to inappropriate treatment and unnecessary costs. If the serum Cr was determined after a recent meat meal, serum Cr measurements should be repeated either after fasting or after meat-free meals that day. Interpretation of treatment effects and progression of CKD will also be affected by the elevation of Cr following the consumption of cooked meat.