Levels of phytoestrogens, inorganic trace-elements, natural toxicants and nitrate in vegetarian duplicate diets

Abstract

Vegetarian duplicate diets were collected in summer (16) and winter (19) and were analysed for the levels of 13 phytoestrogens, nitrate, 12 trace elements, two glycoalkaloids and three furanocoumarins. Phytoestrogens were analysed by paired hydrolysed and non-hydrolysed assays. The mean total isoflavone concentration in diets, without hydrolysis, was 14 mg kg −1 in summer and 15 mg kg −1 in winter, corresponding to an overall hydrolysed aglycone concentration of 10 mg kg −1. The tin concentration was higher in winter than in summer diets at 4.6 and 2.2 mg kg −1. The nitrate concentration was 51 mg kg −1 in summer and 45 mg kg −1 in winter. The furanocoumarins psoralen, xanthotoxin and bergapten were present at a combined average concentration of 0.075 mg kg −1. The glycoalkaloid α-chaconine was observed in only one sample at 14 mg kg −1 with an LOD of 0.8 mg kg −1. Only minor compositional differences were observed between the summer and winter diets. Daily intakes were calculated and these values were compared with existing compositional data on food and with the appropriate recommended safe exposure levels. For isoflavones a mean aglycone equivalent intake of 10.5 mg day −1 was calculated. The mean tin intake was significantly higher in winter than in summer at 5.5 and 2.1 mg day −1. Nitrate intake from these diets was 53 mg day −1, if the theoretical liquid portion of diet were considered, the resulting estimated total of 84 mg day −1 is similar to that of the UK average. Other than an increase in tin intake during winter, exposure of vegetarians to individual phytoestrogens, natural toxicants and inorganic trace-elements was comparable to that of the general population. No individual level of any analyte in any single diet sample exceeded recommended intake levels.