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Access Type

WSU Access

Date of Award

January 2020

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Nutrition and Food Science

First Advisor

Pramod Khosla

Abstract

In the United States, African Americans (AA) suffer a disproportionate burden of ESRD, accounting for 35% of all dialysis patients, and are 3.7 times more likely to progress to ESRD than whites. This increase in CKD risk is partially attributed to higher rates of hypertension, diabetes mellitus, and cardiovascular disease. Paradoxically, once on hemodialysis, AA have a survival advantage over whites, likely due to multiple factors including nutritional status, inflammation, psychosocial status, and genetic variation.

Although both the dialysis procedure and pharmacological treatments are effective at reducing the uremic toxin load, HD patients are still encouraged to adhere to strict dietary guidelines. In an effort to avoid foods high in phosphorus and potassium, patients requiring HD have limited intakes of fruits, vegetables, nuts, legumes, dairy, and whole grains. Associated with reduced consumption of foods naturally rich in phytochemicals, such as carotenoids and polyphenols, is a potential for the loss of benefit from the antioxidant and anti-inflammatory activities associated with their intake.

ESRD patients on HD suffer from excessive oxidative stress, which has been associated with an increased risk for cardiovascular disease. Mortality due to CVD is 20 times higher than in the general population due to both traditional and nontraditional risk factors such as protein energy wasting, insulin resistance, anemia, oxidative stress, and inflammation. The HD procedure itself results in a significant loss of antioxidants, while the bioincompatibility of dialyzers and dialysate trigger the production of free radicals.

Nutritional approaches to improve outcomes for ESRD patients on HD have evolved over time and reflect technological advances in renal replacement therapy. Focus in research has shifted from restriction of individual nutrients and foods to examining diet patterns associated with improved outcomes and mortality.

Two main analytical approaches used to identify dietary patterns in nutritional epidemiology are à priori (hypothesis-driven) and à posteriori (data-driven) methods. À priori methods are based on indices of diet quality or nutritional health defined scores and assess the extent to which a subject complies with the predefined dietary pattern, whereas à posteriori methods use multivariate statistical techniques to derive dietary patterns empirically based on the actual diet in a specific population.

Health outcomes in AA maintenance hemodialysis patients and derived dietary patterns using both an à posteriori and an à priori method were examined.

The Dietary Inflammatory Index (DII), à priori method, failed to show any correlation with inflammatory or anthropometric indices. DII showed a mean score of 3.1 ± 1.1 with a range of -0.54 to 5.83, indicating patients consumed a proinflammatory diet. The null association between diet and inflammatory markers (CRP, MCP-1, IL-6 and IL-18) may reflect that the inflammatory contribution from the diet is overshadowed by the production of inflammatory molecules in the uremic milieu.

A cluster analysis, an à posteriori method, was performed using the k-means algorithm, a nonhierarchical clustering method which classifies participants into non-overlapping groups based on Euclidean distance, to obtain dietary patterns. Two major dietary patterns were identified: (Cluster 1) a high “sugar sweetened beverage” pattern (hiSSB) and (Cluster 2) a low “sugar sweetened beverage” pattern (loSSB). The hiSSB dietary pattern was characterized by higher energy contributions from calorically sweetened soft and juice drinks (p< 0.001) and poultry (p< 0.05), whereas the greatest energy contributors to the loSSB group was unprocessed red meat (p< 0.05), fish and shellfish, (p< 0.05), and custard style desserts such as puddings, ice cream, and cheesecake (p< 0.05). Compared to those in the loSSB dietary pattern cluster, patients in the hiSSB cluster scored lower baseline values on all five KDQOL domains and significantly lower on the S12 mental composite domain (p < 0.026).

All dietary analyses demonstrated that the majority of patients consumed an energy dense diet, deficient in several micronutrients as most calories were derived from sugar sweetened beverages and processed foods. Future studies aimed at interventions to examine the effects of liberalizing the standard renal diet to deemphasize phosphorus and potassium rich foods and allow whole and minimally processed foods are needed.

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