Date of Award

2015

Document Type

Thesis

Degree Name

Master of Science (MS) in Biology

Department

Biology

Abstract

"Since divergence from our ancestral lineage ~ 2.8 mya, humans have relied on foraged foods to obtain dietary mineral nutrition. Around 12,000 years ago, people began shifting towards a lifestyle of food production. The rapid shift in lifestyle significantly altered the human diet, and research suggests our genomes have had insufficient time to adjust. Due to the discord between genome and environment, unprecedented levels of disease and malnutrition are epidemic in certain subsets of the population. Studies suggest the most cost effective way to mitigate the risk of these diseases is to find ways to increase micronutrient consumption. As a class, wild plant foods appear to be more nutrient dense than most modern foods, so including or reintroducing wild foods into the human diet should provide a number of health benefits. Unfortunately, little is known about the dietary mineral composition of many foraged food plants and even less is known about potential differences in nutrient composition between populations or across the phenology. The Western Spring Beauty (Claytonia lanceolata) is no exception, whereas some information from a proximate analysis conducted in 1938 exists, data about micronutrient composition is altogether lacking. Indigenous people harvested the corms (underground stems) of C. lanceolata since prehistory to eat immediately, store for delayed consumption, or use as a trade good. Due to the prevalence of its historic use, we hypothesized that C. lanceolata corms would be rich in dietary mineral nutrition, and compare favorably to cultivated food plants. We also expected differences in the average dietary mineral content of corms from different populations, due to the heterogeneity of the environments where C. lanceolata grows. Lastly, we expected differences in mean dietary mineral content of corms across their phenology due to use/storage of dietary minerals over the course of the flowering cycle. To test these predictions, we sampled 12 populations across the Columbia Plateau region of North America. We resampled six populations about 30 days after our initial harvest. Corms were assayed for dietary mineral and toxic metal content using standard ICP-OES methods. We found that a single serving of corms (100 g fresh weight) likely provided between 10-25% of the DRI for Mg, P, Cu, and Zn, and over 100% of the DRI for Fe and Mn. These values compare favorably to modern foods. The average content of macroelements did not vary significantly with mode of preparation (i.e. removal of the periderm), yet concentrations of trace elements Fe, Cr, Cu, Mn, and Pb in the samples was significantly higher (p<.001 for Fe, Cr, Pb, Al; p=.003 Cu; p=.007 Mn) between samples with periderm intact and samples with the periderm removed. The average amount of Pb in the samples was significantly reduced (p<.001) when the periderm was removed prior to analysis. Of the six populations resampled, the average amount of most macroelements and one trace element contained in the corms increased significantly (Na; p=.05, Ca; p=.004, Mg; p=.015, K; p=.006, Cu; p=.043) in the late samples. Concentrations of toxic metals did not change significantly between sample times. The mean weight of corms was significantly different among populations (p<.001). Averages concentration of macroelements (Ca; p=.04, Mg; p<.001, K; p=.004, Na; p=.004 , P; p=.013), trace elements (Fe; p=.004, Mn; p=.023, Zn; p<.001) and toxic metals (Cd, Pb, Ba, Al; p<.001) differed significantly by sample location. These results suggest that corms are a viable but highly variable source of nutrition. Consumption of corms can increase health by displacing less nutritious modern foods, and could increase micronutrient consumption. Corms may mitigate the risk of common deficiencies, especially when preparation method, time of harvest, and place of harvest are considered. Our results call into question the validity of previous studies with low replicate samples"--Leaves iii-iv.

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Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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