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Am J Phys Anthropol. 2015 Nov;158(3):371-85. doi: 10.1002/ajpa.22805. Epub 2015 Jul 14.

Assessing digestibility of Hadza tubers using a dynamic in-vitro model.

Author information

Plant Foods in Hominin Dietary Ecology Research Group, Max Planck Institute for Evolutionary Anthropology, Leipzig, 04103, Germany.
Metabolism, Anthropometry, and Nutrition Laboratory, Department of Anthropology, University of Nevada, Las Vegas, Nevada, 89154-5003.
Department of Pharmacokinetics & Human Studies, TNO Healthy Living, Zeist, NL-3704 HE, The Netherlands.
Division of Biological Anthropology, University of Cambridge, Cambridge, Cb2 1TN, UK.



Bioaccessibility is a useful measure for assessing the biological value of a particular nutrient from food, especially foods such as tubers. The wild tubers exploited by Hadza foragers in Tanzania are of interest because they are nontoxic, consumed raw or briefly roasted, and entail substantial physical barriers to consumers. In this study, we attempted to elucidate the biological value of Hadza tubers by measuring the absorption of glucose through in-vitro digestion.


We quantified digestibility using data from 24 experimental trials on four species of Hadza tuber using a dynamic in-vitro model that replicates digestion in the stomach and small intestine. Analysis of glucose in the input meal and output dialysate revealed the accessible glucose fraction. We also conducted assays for protein, vitamin, and mineral content on whole tubers and meal fractions.


Bioaccessibility of glucose varies depending on tuber species. Holding effects of chewing constant, brief roasting had negligible effects, but high intraspecific variation precludes interpretive power. Overall, Hadza tubers are very resistant to digestion, with between one- and two-thirds of glucose absorbed on average. Glucose absorption negatively correlated with glucose concentration of the tubers.


Roasting may provide other benefits such as ease of peeling and chewing to extract edible parenchymatous tissue. A powerful factor in glucose acquisition is tuber quality, placing emphasis on the skill of the forager. Other nutrient assays yielded unexpectedly high values for protein, iron, and iodine, making tubers potentially valuable resources beyond caloric content.


TIM-1; bioaccessible; cooking; hunter-gatherer; wild plant foods

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