A study in Frontiers in Nutrition has shown for the first time that elevated consumption of added sugars should probably be added to the list of risk factors for kidney stones.

Kidney stones affect between 7% and 15% of people in North America, 5% to 9% of people in Europe, and 1% to 5% of people in Asia. Severe pain, nausea, vomiting, fever, chills, and bloody urine are all common symptoms.

However, kidney stones do more than just diminish the quality of life; they can also cause infections, swelling kidneys (hydronephrosis), renal insufficiency, and end-stage renal disease.

Being an adult male, obesity, persistent diarrhoea, dehydration, and having inflammatory bowel disease, diabetes, or gout are all known risk factors for developing kidney stones.

Added sugars occur in many processed foods, but are especially abundant in sugar-sweetened sodas, fruit drinks, candy, ice cream, cakes, and cookies.

“Ours is the first study to report an association between added sugar consumption and kidney stones,” said lead author Dr Shan Yin, a researcher at the Affiliated Hospital of North Sichuan Medical College, Nanchong, China. “It suggests that limiting added sugar intake may help to prevent the formation of kidney stones.”

National Health and Nutrition Examination Survey Yin et al. analysed epidemiological data on 28,303 adult women and men, collected between 2007 to 2018 within the US National Health and Nutrition Examination Survey (NHANES).

Participants self-reported if they had a history of kidney stones. Each participant’s daily intake of added sugars was estimated from their recall of their most recent consumption of food and drinks, given twice: once in a face-to-face interview, and once in a telephone interview between three and 10 days later. For example, participants were asked if they had eaten syrups, honey, dextrose, fructose, or pure sugar during the past 24 hours.

Each participant also received a healthy eating index score (HEI-2015), which summarises their diet in terms of the adequacy of beneficial diet components such as fruits, vegetables, and whole grains, and moderation of potentially harmful foods, for example, refined grains, sodium, and saturated fats.

The researchers adjusted the odds of developing kidney stones per year during the trial for a range of explanatory factors. These included gender, age, relative income, BMI, HEI-2015 score, smoking status, and whether the participants had a history of diabetes.

At the start of the study, participants with a higher intake of added sugar tended to have a higher current prevalence of kidney stones, a lower HEI score, and a lower education level. The overall mean intake of added sugars was 272.1 calories per day, which corresponds to 13.2% of the total daily energy intake.

The positive association between added sugars and kidney stones The researchers showed that after adjusting for these factors, the percentage of energy intake from added sugars was positively and consistently correlated with kidney stones.

For example, participants whose intake of added sugars was among the 25% highest in the population had 39% greater odds of developing kidney stones over the course of the study.

Similarly, participants who derived more than 25% of their total energy from added sugars had 88% greater odds than those who derived less than 5% of their total energy from added sugars.

The mechanisms of the relation between consuming more added sugars and a greater risk of developing kidney stones are not yet known. Because this was an uncontrolled observational trial, it can’t yet be ruled out that unknown confounding factors might drive this association.

“Further studies are needed to explore the association between added sugar and various diseases or pathological conditions in detail,” cautioned Yin. “For example, what types of kidney stones are most associated with added sugar intake? How much should we reduce our consumption of added sugars to lower the risk of kidney stone formation? Nevertheless, our findings already offer valuable insights for decision-makers.”