The Other Red Meat: Pork Tied to Kidney Decline

Editor's Note: For almost every chronic disease, there is at least one dietary restriction or a special diet outlining what patients should eat. And for kidney disease, one of the recommendations is to restrict protein intake. But do all protein sources pose the same risk in chronic kidney disease (CKD) progression? Or do some sources of protein carry a significantly higher risk?

In a recent study published online in the Journal of the American Society of Nephrology, "Red Meat Intake and Risk of ESRD,"^[1] a team led by senior author Woon-Puay Koh, MBBS (Hon), PhD, of Duke-NUS Medical School and Saw Swee Hock School of Public Health, National University of Singapore, concluded that among all sources of protein, red meat consumption was strongly associated with an increased risk for end-stage renal disease (ESRD).

Medscape interviewed Dr Koh, an epidemiologist and site principal investigator in the large National Institutes of Health–funded Singapore Chinese Health Study, to discuss her study findings in more detail.

Medscape: What were the findings in your recent study regarding red meat intake and risk for ESRD?

Dr Koh: We found that while the total amount of protein intake was not clearly related to risk for ESRD, the consumption of red meat had a step-wise, dose-dependent association with increased risk for ESRD. Participants consuming the highest amounts (top 25%) of red meat had a 40% increased risk of developing ESRD compared with people consuming the lowest amounts (lowest 25%). There was no such association with consumption of other protein sources such as poultry, fish/seafood, eggs, and dairy products, while the results of plant-based protein sources, soy and legumes, seemed to suggest that these food items could be slightly protective.

When we conducted substitution analysis—where one serving of red meat was replaced with one serving of another food source of protein per day; namely, poultry, fish/seafood, eggs, or soy/legumes—we found that the risk for ESRD was reduced significantly by about 50%-62%. However, I must stress that our study does not indicate that eating other meats is good for preserving kidney function. Rather, because other meats do not increase the risk for ESRD, they are good replacements for red meat.

Medscape: When we think of "red meat," we immediately think of beef. However, we noticed that pork was the most common type of red meat consumed by the participants in your study. Is this correct?

Dr Koh: From a previous study, we have estimated that 97% of red meat intake in this population consisted mainly of pork. This is because our study cohort is a middle-aged and elderly Chinese population where the participants may choose to abstain from beef due to religious reasons.

Medscape: Many dietitians in the United States refer to pork as "the other white meat," with the impression that it is a healthier alternative to beef. What are your thoughts on the renal risks of pork compared with beef?

Dr Koh: Most studies on red meat in Western populations focus on beef, as this is the main type of red meat consumed, although pork is included with beef in red meat. Conversely, in our study population, the main type of red meat consumed is pork, although we have included beef and other red meat, such as mutton or lamb, in our computation of red meat intake. To my best knowledge, no single study has differentiated between beef and pork in affecting risk for disease as these two types of meat are grouped together as red meat in epidemiologic studies.

Medscape: Studies have shown that eating grilled or barbequed meat is associated with increased risk for kidney cancer. How was the meat prepared/sourced in the study (grilled, baked, fried; processed or organic)? And how might this have affected the results?

Dr Koh: Our previously published results have shown that the methods of cooking for red meat, poultry, or fish in this population were similar. Hence, we do not think that the method of cooking red meat plays a significant role in the risk for ESRD, nor does it explain the differences in ESRD risks with different types of meat consumed in this study. Future studies are needed to investigate the underlying mechanisms as to how specific compounds present in red meat may deteriorate renal function.

Medscape: What have previous studies shown regarding a potential link between meat consumption and kidney dysfunction?

Dr Koh: Our finding of a strong positive relationship between red meat intake and ESRD incidence is largely consistent with the results of studies in the United States that have examined the effect of animal protein, and found that a diet consisting of higher intake of red meat was associated with a higher decline in kidney function or increased risk of mortality in patients with CKD.

Specifically, The Nurses' Health Study in the United States found that women with a mostly Western-style diet, which consisted of a higher intake of red and processed meats, saturated fats, and sweets, had a higher risk for decline in estimated glomerular filtration rate than the women who kept to a mostly DASH-style diet, which consisted of a higher intake of vegetables, fruits, and whole grains.^[2] A dietary pattern consisting mostly of processed and fried foods, organ meats, and sweets, also known as the Southern-style diet, has also been found to be associated with an increased risk for mortality in patients with CKD.^[3]

Medscape: What are the clinical implications of your study? Is there a specific type of diet to recommend to patients with kidney disease?

Dr Koh: Our findings suggest that patients with early stage of CKD or the general population worried about kidney health can still maintain protein intake but consider switching to plant-based sources. However, if they still choose to eat meat, fish/shellfish and poultry are better alternatives to red meat. The message is not to avoid red meat like poison but to eat red meat in moderation and best not make it the single meat item at every meal or main protein source every day. For a healthy diet, it is best to eat a variety of food sources for dietary protein.

Follow Anya Romanowski on Twitter @Anya13
And for more Nephrology news: @MedscapeKidney

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