Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, Ontario, Canada.
PLoS One. 2020 Aug 10;15(8):e0237105. doi: 10.1371/journal.pone.0237105. eCollection 2020.
Studying the isotope variability in fast-growing human tissues (e.g., hair, nails) is a powerful tool to investigate human nutrition. However, interpreting the controls of this isotopic variability at the population scale is often challenging as multiple factors can superimpose on the isotopic signals of a current population. Here, we analyse carbon, nitrogen, and sulphur isotopes in hair from 590 Canadian resident volunteers along with demographics, dietary and geographic information about each participant. We use a series of machine-learning regressions to demonstrate that the isotopic values in Canadian residents' hair are not only influenced by dietary choices but by geographic controls. First, we show that isotopic values in Canadian residents' hair have a limited range of variability consistent with the homogenization of Canadian dietary habits (as in other industrialized countries). As expected, some of the isotopic variability within the population correlates with recorded individual dietary choices. More interestingly, some regional spatial patterns emerge from carbon and sulphur isotope variations. The high carbon isotope composition of the hair of eastern Canadians relative to that of western Canadians correlates with the dominance of corn in the eastern Canadian food-industry. The gradient of sulphur isotope composition in Canadian hair from coast to inland regions correlates with the increasing soil pH and decreasing deposition of marine-derived sulphate aerosols in local food systems. We conclude that part of the isotopic variability found in the hair of Canadian residents reflects the isotopic signature associated with specific environmental conditions and agricultural practices of regional food systems transmitted to humans through the high consumption rate of intra-provincial food in Canada. Our study also underscores the strong potential of sulphur isotopes as tracers of human and food provenance.
研究快速生长的人体组织（如头发、指甲）中的同位素变异性是研究人类营养的有力工具。然而，在人群层面上解释这种同位素变异性的控制因素通常具有挑战性，因为多种因素可能会叠加在当前人群的同位素信号上。在这里，我们分析了 590 名加拿大居民志愿者的头发中的碳、氮和硫同位素，以及每个参与者的人口统计学、饮食和地理信息。我们使用一系列机器学习回归来证明加拿大居民头发中的同位素值不仅受到饮食选择的影响，还受到地理控制的影响。首先，我们表明加拿大居民头发中的同位素值的变化范围有限，与加拿大饮食习惯的同质化一致（与其他工业化国家一样）。正如预期的那样，人群中的一些同位素变异性与记录的个体饮食选择相关。更有趣的是，碳和硫同位素变化中出现了一些区域空间模式。与加拿大西部相比，加拿大东部居民头发中的高碳同位素组成与东部加拿大食品工业中玉米的主导地位相关。加拿大头发中从沿海到内陆地区的硫同位素组成梯度与当地食物系统中土壤 pH 值的升高和海洋来源硫酸盐气溶胶沉积的减少相关。我们得出结论，在加拿大居民头发中发现的部分同位素变异性反映了与区域食物系统中特定环境条件和农业实践相关的同位素特征，这些特征通过加拿大省内食物的高消耗率传递给人类。我们的研究还强调了硫同位素作为人类和食物来源示踪剂的强大潜力。
