Department of Biology, University of Ottawa, Ottawa, K1N 6N5, Canada.
Department of Anthropology, The University of Texas, San Antonio, TX, 78249, USA.
Environ Geochem Health. 2018 Apr;40(2):803-813. doi: 10.1007/s10653-017-0025-4. Epub 2017 Oct 4.
Geophagy, the deliberate consumption of earth materials, is common among humans and animals. However, its etiology and function(s) remain poorly understood. The major hypotheses about its adaptive functions are the supplementation of essential elements and the protection against temporary and chronic gastrointestinal (GI) distress. Because much less work has been done on the protection hypothesis, we investigated whether soil eaten by baboons protected their GI tract from plant secondary metabolites (PSMs) and described best laboratory practices for doing so. We tested a soil that baboons eat/preferred, a soil that baboons never eat/non-preferred, and two clay minerals, montmorillonite a 2:1 clay and kaolinite a 1:1 clay. These were processed using a technique that simulated physiological digestion. The phytochemical concentration of 10 compounds representative of three biosynthetic classes of compounds found in the baboon diet was then assessed with and without earth materials using high-performance liquid chromatography with diode-array detection (HPLC-DAD). The preferred soil was white, contained 1% halite, 45% illite/mica, 14% kaolinite, and 0.8% sand; the non-preferred soil was pink, contained 1% goethite and 1% hematite but no halite, 40% illite/mica, 19% kaolinite, and 3% sand. Polar phenolics and alkaloids were generally adsorbed at levels 10× higher than less polar terpenes. In terms of PSM adsorption, the montmorillonite was more effective than the kaolinite, which was more effective than the non-preferred soil, which was more effective than the preferred soil. Our findings suggest that HPLC-DAD is best practice for the assessment of PSM adsorption of earth materials due to its reproducibility and accuracy. Further, soil selection was not based on adsorption of PSMs, but on other criteria such as color, mouth feel, and taste. However, the consumption of earth containing clay minerals could be an effective strategy for protecting the GI tract from PSMs.
食土，即故意食用土壤物质，在人类和动物中都很常见。然而，其病因和功能仍知之甚少。关于其适应功能的主要假设是补充必需元素和保护免受暂时和慢性胃肠道（GI）不适。由于对保护假说的研究较少，我们调查了狒狒食用的土壤是否能保护它们的胃肠道免受植物次生代谢物（PSMs）的侵害，并描述了进行此类研究的最佳实验室实践。我们测试了狒狒食用/偏好的土壤、狒狒从不食用/不偏好的土壤以及两种粘土矿物，蒙脱石（2:1 型粘土）和高岭石（1:1 型粘土）。这些土壤都采用了一种模拟生理消化的技术进行处理。然后，使用高效液相色谱-二极管阵列检测（HPLC-DAD），评估了代表狒狒饮食中三种生物合成类化合物的 10 种化合物的植物化学成分，有无土壤材料的情况下各有多少。偏好的土壤呈白色，含有 1%的岩盐、45%的伊利石/云母、14%的高岭石和 0.8%的沙子；不偏好的土壤呈粉红色，含有 1%的针铁矿和 1%的赤铁矿，但没有岩盐，40%的伊利石/云母、19%的高岭石和 3%的沙子。极性酚类和生物碱的吸附水平通常比非极性萜类化合物高 10 倍。就 PSM 吸附而言，蒙脱石比高岭石更有效，高岭石比不偏好的土壤更有效，不偏好的土壤比偏好的土壤更有效。我们的研究结果表明，由于其重现性和准确性，HPLC-DAD 是评估土壤对 PSM 吸附的最佳实践。此外，土壤的选择不是基于 PSM 的吸附，而是基于颜色、口感和味道等其他标准。然而，食用含有粘土矿物的土壤可能是保护胃肠道免受 PSM 侵害的有效策略。
