, even after adjustment for confounding factors.
- Researchers identified 402,982 participants in the UK Biobank from March 2006 to October 2010 who had completed a questionnaire about the frequency with which they added salt to food and who did not have diabetes, chronic kidney disease, cancer, or cardiovascular disease at baseline.
- Urine samples were collected at baseline, sodium and potassium levels were measured, and 24-hour sodium excretion was estimated.
- Investigators followed participants from baseline to diagnosis of diabetes, death, or the censoring date (May 23, 2021), whichever occurred first. Information on T2D events were collected through medical history linkage to data on hospital admissions, questionnaire, and the death register.
- During a mean follow-up of 11.9 years, 13,120 incident cases of T2D were documented.
- Compared with people who reported “never/rarely” adding salt to food, the sex- and age-adjusted hazard ratios (HRs) for developing T2D were 1.20, 1.32, and 1.86 for those who reported “sometimes,” “usually,” and “always” adding salt, respectively (P-trend < .001).
- After further adjustment for the Townsend deprivation index, education level, income, smoking, drinking, physical activity, and high cholesterol, the association was attenuated but remained significant, with HRs of 1.11, 1.18, and 1.28 for “sometimes,” “usually,” and “always” responses, respectively (P-trend < .001).
- After full adjustment, there was also a dose-dependent relationship across quintiles of urinary sodium and higher T2D risk, with HRs of 1 (reference), 1.12, 1.17, 1.28, and 1.34 for quintiles 2-5, respectively (P-trend < .001).
- Body fat percentage and body fat mass significantly mediated the association of adding salt with T2D, by estimated effects of 37.9% and 39.9%, respectively (both P < .001).
“These findings provide support that reduction of adding salt to foods may act as a potential behavioral intervention approach for preventing T2D. Future clinical trials are needed to further validate our findings,” the authors wrote.
The study by Xuan Wang, MD, PhD, department of epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, and colleagues was published in the November 2023 issue of Mayo Clinic Proceedings.
The researchers could not completely exclude the possibility that high frequency of adding salt to foods is a marker for an unhealthy lifestyle. Self-reported frequency of adding salt to food might be subject to information bias and did not provide quantitative information on total sodium intake. In addition, participants were mainly of European descent, making application of the findings to other ethnic groups unclear; the observational design meant researchers could not rule out residual confounding; and information on addition of salt to food was available only at baseline, so potential changes in salt consumption during follow-up could not be considered.
The study was supported by grants from the National Heart, Lung, and Blood Institute; the National Institute of Diabetes and Digestive and Kidney Diseases; the Fogarty International Center; and Tulane Research Centers of Excellence Awards. The authors reported no potential competing interests.
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