Reading tea leaves: Assessing the impact of tea consumption on strontium isotopes and concentrations

Strontium (Sr) is ubiquitous in our ecosystem, and its presence at the very basis of the food chain in plants and water ensures its integration into the human body. Dietary Sr dominates the Sr input of skeletal tissues, mainly through the consumption of plants. Consumption of specific foodstuffs on a regular basis, such as imported foods, can influence 87Sr/86Sr or [Sr] in the body towards exogenous values, as has been demonstrated with marine products and salt. In these instances, the consumption of such products, if not properly accounted for, can affect the archaeological interpretations of results in mobility and dietary analyses. Tea is a popular drink whose consumption has been dated back to the Warring States Period (475-221 BC) in China. Gradually spreading across all continents, it is today the second most consumed drink after water in the world. The cultivation of the Camellia sinensis L. shrub can only be achieved in tropical and subtropical areas, resulting in the importation of tea. As a beverage made from the brewing of these imported leaves and consumed on a regular basis, tea may affect Sr isotopic and concentration values of consuming populations. This pilot study presents 87Sr/86Sr, [Sr], and δ88Sr data for various types of tea and herbal teas, and how the brewing process influences the Sr values in the final consumed beverage. This is the first step in exploring the potential impact of tea consumption on the interpretation of Sr data.