Pam Harrison

November 13, 2015

SAN DIEGO — There is an association between the consumption of red meat and the risk for end-stage renal disease (ESRD) in people of Chinese origin in the general population of Singapore, new research shows.

"A number of organizations have advocated reducing protein intake in patients with pre-existing chronic kidney disease in order to delay progression to ESRD," said Quan Lan Lew, MD, from the Duke–National University of Singapore Graduate Medical School.

"We found that a high intake of red meat appears to increase ESRD risk, and that replacement of red meat protein with other sources of protein has the potential to reduce this risk," she reported.

Dr Lew presented the study results at the Kidney Week 2015.

The researchers used data from the 60,198 participants recruited from 1993 to 1998 to the Singapore Chinese Health Study, a large population-based prospective cohort of people of south Chinese descent. Participants were 45 to 74 years of age.

The 165-item food frequency questionnaire was used to collect information on the consumption of specific foods, the number of servings consumed, and the portion sizes consumed.

Record linkage with the nationwide Singapore Renal Registry, up to December 2012, was used to identify 951 cases of incident ESRD during a mean follow-up of 15.5 years.

Patients who developed ESRD tended to be slightly older than those who did not, and were more likely to have smoked at some point, to have hypertension, diabetes, or both, and to be slightly heavier, Dr Lew reported.

In their basic model, the researchers found a significant correlation between ESRD risk and the highest three quartiles of any protein intake after adjustment for age, sex, dialect, educational level, and year of interview.

Red Meat, Not Other Proteins

However, when they adjusted "for variables such as lifestyle and chronic disease, we found that this adjustment attenuated any positive correlation," Dr Lew said, except in the case of red meat intake.

In fact, the relative risk for ESRD was 40% higher in the highest quartile of red meat intake than in the lowest quartile. The association between a high intake of red meat and ESRD risk remained consistent even when participants with underlying comorbidities were excluded from the analysis.

This positive correlation was not seen for poultry, fish or shellfish, eggs, dairy products, or soy and legumes, Dr Lew explained.

Substituting a serving of red meat with a serving of poultry, for example, decreased the relative risk for ESRD by approximately 66% (P < .001), with legumes decreased the relative risk by 54% (P < .001), with fish decreased the relative risk by 52% (P = .002), and with eggs decreased the relative risk by 52% (P = .009).

"Very few people in Singapore eat beef on a regular basis," said Dr Lew, noting that in the Singapore Chinese Health Study, "red meat" referred mainly to pork.

"Future directions will be to determine the pathophysiology of eating red meat on ESRD risk and to see if substituting red meat with other sources of protein in patients with chronic kidney disease might delay progression to ESRD," she said.

Acidification in the Kidney

"When the kidney is challenged with acid — such as by eating an animal-source protein diet — the kidney increases levels of hormones that help it excrete the acid in the short term," said Donald Wesson, MD, chief academic officer at Baylor Scott & White Health in Dallas, who has been studying how the kidney adjusts to either a high or a low acid challenge for the past 30 years.

However, in the long-term, high levels of these hormones worsen kidney function, he told Medscape Medical News.

The thinking has been that if patients simply reduce the total amount of protein in their diet, it will help protect kidney function over the long term, he explained. But lowering the total amount of protein in the diet did not reduce the rate of kidney disease progression in the Modification of Diet in Renal Disease study, which was conducted in the early 1990s.

Our studies suggest that it is the quality, not the quantity, of the protein that is important.

In contrast, Dr Wesson reported that his own research has shown that fruit and vegetable sources of protein offer a base rather than an acid challenge to the kidney. "If you add fruit and vegetables to the diet, we found that they are protective of kidney function," he said.

Thus, contrary to what the "gospel" has been in the kidney community regarding the toxic effects of protein on kidney function, "our studies suggest that it is the quality, not the quantity, of the protein that is important. We say that the prescription should be for people to eat more fruits and vegetables as sources of protein and less animal protein," he said.

Dr Wesson said he is unable to speculate why red meat and not other sources of animal protein affected ESRD risk in the Singapore study. But he did suggest that red meat is particularly high in its acid-producing potential, compared with other sources of animal protein, which would make it especially toxic to the kidney.

The study was funded with the help of non-US government support. Dr Lew and Dr Wesson have disclosed no relevant financial relationships.

Kidney Week 2015: American Society of Nephrology Annual Meeting. Abstract FR-OR109. Presented November 6, 2015.


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