GFR Decline Tied to Protein Intake in Diabetic Blacks

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In a study, the percentage decline in eGFR over an 8-year period was greater among blacks with vs without diabetes across all quintiles of protein intake.
In a study, the percentage decline in eGFR over an 8-year period was greater among blacks with vs without diabetes across all quintiles of protein intake.

Higher protein intake as a percent of total energy intake is associated with a greater decline in estimated glomerular filtration rate (eGFR) among black individuals with diabetes, new findings suggest.

In a study of 3165 black participants in the Jackson Heart Study (JHS), investigators found that the percentage decline in eGFR over an 8-year period was greater among those with vs without diabetes across all quintiles of protein intake. They also observed a U-shaped dose-response among the participants with diabetes, with the greatest eGFR declines occurring among individuals in the 2 highest and 2 lowest quintiles compared with those in the middle quintile. The investigators observed no association between amount of protein intake and eGFR decline among participants without diabetes.

Protein intake as a percent of total energy intake was 10.7%, 12.7%, 14.3%, 16%, and 18.7% among individuals in the first, second, third, fourth, and fifth quintiles, respectively, Rakesh Malhotra, MD, MPH, of the University of California San Diego, and colleagues reported online ahead of print in the Journal of Renal Nutrition. Among participants with diabetes, mean eGFR declined by 15.9 and 16.7 mL/min/1.73 m2 in the first and second quintiles, respectively, and 19.1 and 20 mL/min/1.73 m2 in the fourth and fifth quintiles, respectively. The mean eGFR decline in the middle quintile was 12 mL/min/1.73 m2.

“Our results suggest that high protein consumption may contribute to the development of kidney disease, especially in AAs [African Americans] with diabetes,” Dr Malhotra's team wrote.

The investigators estimated protein intake from a validated food frequency questionnaire (FFQ) administered at participants' first study visit.

Study strengths include analysis of data from participants in the JHS, a well-characterized large population-based unique cohort of high-risk black people of generally low socioeconomic status, and a relatively long follow-up period, according to the authors. Dr Malhotra and his colleagues also acknowledged some study limitations. “FFQ data were self-reported and prone to misreporting and measurement error,” they pointed out. Also, the FFQ was administered only once, at the first visit, with no updated dietary intake data obtained to study effects of long-term, sustained protein intake, they noted.

Dr Malhotra and collaborators previously conducted a nested case-control study within the Southern Community Cohort Study (SCCS)—a prospective study of low-income blacks and whites in the southeastern United States—demonstrating that a higher percentage protein intake was associated with an increased risk of incident end-stage renal disease, especially among black individuals with diabetes. Each 1% increase in percent energy intake from protein was associated with a significant 6% increased odds of ESRD among blacks with diabetes, the investigators reported in in Nutrition, Metabolism & Cardiovascular Diseases (2016;26:1079-1087). They found no significant association between percent energy intake from protein and ESRD risk among blacks without diabetes and whites with and without diabetes.

References

Malhotra R, Lipworth L, Cavanaugh KL, et al. Protein intake and long-term change in glomerular filtration rate in the Jackson Heart StudyJ Ren Nutr. 2018; published online ahead of print.

http://www.jrnjournal.org/article/S1051-2276(17)30284-4/fulltext

Malhotra R, Cavanaugh KL, Blot WJ, et al. Higher protein intake is associated with increased risk for incidence end-stage renal disease among blacks with diabetes in the Southern Community Cohort Study. Nutr Metab Cardiovasc Dis. 2016;26:1079-1087.

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