Red meat and kidney risk
Analysis of data from the Singapore Chinese Health Study, a prospective study on 63,257 Chinese people living in Singapore, has unearthed a positive association between the amount of red meat consumed and the risk of end-stage renal disease (ESRD). The findings of this study, led by Professor Koh Woon Puay from Duke-NUS Medical School, were published in the Journal of the American Society of Nephrology, the leading kidney journal in the world, on 14 July 2016.
For patients with advanced stage renal failure, advice from doctors usually involves cutting back on protein; and randomised controlled trials have shown evidence that reducing the intake of protein can help to retard the progression of the disease. However, there are limited studies on the impact of consumption of protein on the kidney health of the general population. It is this gap that the team led by Prof Koh, who has a joint appointment with the NUS Saw Swee Hock School of Public Health, has tried to fill with this study.
The study had two aims. First, to determine the relationship between total protein intake and risk of ESRD. Second, to determine if protein from different food sources has an effect on ESRD risk.
An in-depth food frequency questionnaire was conducted, involving 165 food dishes commonly eaten by Chinese. The red meat most eaten by this population was found to be pork, with a 97% intake among all red meat. Red meat in this study referred to pork, beef and mutton.
After follow-up of an average of 15.5 years, the team of researchers determined that while the total amount of protein eaten was not clearly related with risk of ESRD, the consumption of red meat had a step-wise, dose-dependent association with increased risk of ESRD.
The participants with the top 25% of red meat consumption, estimated to consume one serving a day, had a 40% higher likelihood of risk of ESRD when compared with the participants with the lowest 25% of red meat consumption. There was no such association for consumption of other protein sources such as poultry, fish and seafood, eggs and dairy products, while the results of plant-based protein sources, soy and legumes, seemed to suggest they are slightly protective.
When the researchers conducted substitution analysis; where one serving of red meat was replaced with one serving of another protein source per day, namely, poultry, fish and seafood, eggs or soy and legumes, they found that risk of ESRD was reduced significantly by about 50% to 62%.
Despite the results, Professor Koh says it is not necessary to completely remove red meat from one’s diet. “The message is not to avoid red meat like poison,” she said. “Eat red meat in moderation, and it's best not to make it your single meat item at every meal, or main protein source every day. Eat a variety of food sources for dietary protein.”
The team is planning to do follow-up investigations to determine what exactly in red meat leads to ESRD risk. Some hypotheses include acid load, nitrites, nitrates, heme iron and advance glycation end products. They also plan to continue using the Singapore Chinese Health study cohort to look at other lifestyle factors that impact risk of ESRD. Some factors they are currently looking at include body mass index, dietary patterns, amount of sleep and beverages such as coffee and tea.
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