Greater dietary intake of animal protein is associated with an increased risk of kidney stones, according to a study of people in Shanghai, China.

Individuals in the highest quintile of total animal protein intake (dairy and non-dairy) and non-dairy animal protein intake had a significant 16% and 14% increased risk of kidney stone development, respectively, compared with those in the lowest quintile, after adjusting for multiple variables, investigators led by Ryan S. Hsi, MD, of Vanderbilt University Medical Center, Nashville, Tennessee, reported online ahead of print in the Journal of Urology.

In addition, participants in the highest quintile of animal to plant protein ratio and non-dairy animal to plant protein ratio had a significant 17% and 20% increased risk of kidney stone formation, respectively. The study found no association between kidney stone risk and total protein consumption or either dairy protein or plant protein consumption.

“Greater animal protein intakes in this study were associated with incident kidney stone risk, which is even more notable in this study population giving the generally low intakes of animal protein,” Dr Hsi and his colleagues wrote.

The authors added that their findings provide further evidence that the non-dairy component of animal protein is a driver of stone risk, not the dairy component. “However, the possibility of a weak association of dairy proteins cannot be completely ruled out due to low intakes of dairy in this population,” the investigators stated.

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The study included 69,166 women in the Shanghai Women’s Health Study (SWHS) and 58,054 men in the Shanghai Men’s Health Study (SMHS). All participants filed out a validated food frequency questionnaire at baseline. After a mean follow-up of 8 years, physicians diagnosed kidney stones in 1451 women and 1202 men.

The average intakes of animal and plant protein were 31.3 g/day and 48.4 g/day for women, respectively, and 30.8 g/day and 51.3 g/day for men, respectively, according to the investigators.

The lowest quintile of animal protein consumption was a mean intake of less than 19.3 g/day for women and less than 17.2 g/day for men; the highest quintile was a mean intake of 36.8 g/day or higher for women and 36.2 g/day for men. The lowest quintile of non-dairy animal protein consumption was a mean intake of less than 17.4 g/day for women and less than 14.9 g/day for men; the highest quintile was a mean intake of 33.5 g/day or higher for women and 32.7 g/day or higher for men.

With regard to study limitations, the investigators noted that they lacked data on family history, stone composition, and 24-hour urine constituents, “which could have further elucidated inherited and metabolic causes for stone formation.” In addition, the population in Shanghai has  a relatively high socioeconomic status in China, so the findings may not be generalizable to other populations.

Reference

Shu X, Calvert JK, Cai H, et al. Plant and animal protein intakes and risk of incident kidney stones: Results from the Shanghai men’s and women’s health studies. J Urol. 2019. doi: 10.1097/JU.0000000000000493

This article originally appeared on Renal and Urology News