# A cross-sectional study of dietary and urinary soy isoflavones about coal-burning fluorosis in Guizhou, China

## TL;DR

This study found that higher dietary intake of soy isoflavones is linked to a lower risk of coal-burning fluorosis in Guizhou, China.

## Contribution

The study is the first to show an epidemiological link between soy isoflavones and reduced coal-burning fluorosis risk.

## Key findings

- Higher dietary soy isoflavone intake was associated with a 39% lower risk of fluorosis.
- Daidzein, a type of soy isoflavone, showed a similar protective effect.
- Urinary soy isoflavone levels mirrored dietary findings, supporting the association.

## Abstract

Previous research showed soy isoflavones have antioxidant properties beneficial to bone health, but no epidemiological studies reported effects of soy isoflavones on fluorosis. Therefore, the aim of this study was to investigate the relationship between soy isoflavones in diet/urine and coal-burning fluorosis.

A comprehensive cross-sectional study with 896 participants in Zhijin County, Guizhou, China, assessed dietary intake through face-to-face interviews using a 75-item food frequency questionnaire. Urine samples were analyzed for soy isoflavone concentrations by HPLC. Unconditional logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for associations.

We observed a significant inverse association between dietary soy isoflavones and fluorosis. The adjusted OR (95% CI) in the highest quartile of intake compared with the lowest was 0.61 (0.38–0.97) (p-trend = 0.032) for total soy isoflavones intake, 0.59 (0.37–0.95) (p-trend = 0.032) for daidzein intake. Results of soy isoflavones in urine were consistent with the dietary results.

Soy isoflavones are associated with the occurrence of coal-burning fluorosis.