Temporal Change in Iron Content of Vegetables and Legumes in Australia: A Scoping Review

Studies in UK and US have reported a temporal decline in the iron content of plant-based foods. Limited research on this topic has been conducted in Australia. The aim of this scoping review was to provide a comprehensive evaluation on the temporal change in iron content of Australian vegetables and legumes from 1900 onward. A systematic search of electronic databases, websites, backward reference searching, and Australian food composition tables was conducted. A total of 34 articles and six versions of Australian food composition databases published between 1930s to 2021, were included in this review. Overall, iron content of vegetables and legumes were assessed at limited time points and geographical origin, cultivars, sampling and analytical techniques varied across studies. The majority of vegetables had similar iron content between two or more timepoints but decreases of 30-50% were noted for sweet corn, red-skinned potatoes, cauliflower and green beans while increases of 150-300% were seen for Hass avocadoes, mushrooms and silverbeet. More pronounced reductions in iron content were observed for legumes, with higher and more variable values reported pre-2000 compared to recent years. Due to limited data and variations in sampling and analytical techniques, no definitive conclusions could be established. As plant-based diets are becoming more popular, consistent monitoring of the nutrient composition of staple plant-based foods is strongly recommended.