Supplementary material for : Development of an assay for Soy Isoflavones in Women's Hair and validation of a French Dietary Habits Inquiry

Abstract: Soy isoflavones have estrogenic and anti-thyroidal effects in animals and humans that can be beneficial or adverse, depending on consumers’ physiological status. Hence, knowing the consumers’ isoflavones exposure can help when looking for health issues related to estrogenic or thyroidal effects. Several extraction methods were tested on 60 volunteer’s hair samples from a hairdresser and from the clinical trial 2017T2-29. The acidic digestion method was the most efficient regarding isoflavones. A dietary habit inquiry was developed based on the analysis of 12,707 food labels from France. A score for the consumer’s exposure to isoflavones was built considering, among other parameters, soy-based diet and foodstuff containing soy as an ingredient, i.e. “hidden-soy”. The correlation between this score and isoflavones measurements in hair reached 0.947; p<0.001. Therefore, providing that relevant data are considered to assess isoflavones exposure, hair which smoothen daily isoflavones intakes’ variations, is a relevant tissue to assess human isoflavones exposure for subsequent health analysis.