Increasingly, the field of nutrition has come to recognize that a variety of factors influence an individual’s response to dietary intake and therefore, that a precision nutrition approach may be superior to broad population-level dietary recommendations in identifying an ideal dietary pattern to maintain optimal health and prevent disease. However, the ability to implement predictive precision nutrition approaches is constrained by limitations in the understanding of how different foods and dietary patterns affect various metabolic processes within an individual and between individuals. The research in this dissertation contributes to that understanding by describing the effects of dietary intake on factors that regulate metabolic responses and by interrogating between group differences in response. Chapter 1 contributes a systematic review of 22 studies in the published literature describing microRNA responses to both acute and long-term dietary interventions within human subjects. Chapter 2 used samples collected from a 16-week trial comparing supplementation with almonds to a calorie matched carbohydrate control to investigate the stability of fasting microRNA levels within pathways related to inflammation and cholesterol metabolism. Chapter 3 investigated glucose and insulin responses to grapes, grape juice, and a standard glucose beverage in the post-prandial period to investigate intra-individual differences in response and the sensitivity of microRNA response within inflammatory pathways following a diet challenge. Chapter 4 examined the relationship between nutritional phenotypes of post-prandial bile acids and fasting blood and insulin levels.

Diet and lifestyle choices are major factors contributing to the risk of cardiovascular disease, which is responsible for more deaths in the United States than any other cause. One dietary component that has received considerable attention for its potential cardioprotective effects is soybeans, which contain lean vegetable protein, dietary fiber and bioactive compounds known as isoflavones. Recent research investigating the relationship between soy and cardiovascular disease has identified several potential mechanisms for the observed protective effects, including cholesterol-lowering properties, antioxidant activity and gene regulation. This review highlights current understanding of the complex relationship between soy and the risk of cardiovascular disease.

College students are at an increased risk for experiencing acute or chronic food insecurity (FI) due to the underlying economic pressures of higher education, including the expensive cost of tuition and inflated cost of living in proximity to a college campus. Driven by the newfound autonomy over dietary choices and purchasing behaviors, and often perpetuated by limited nutrition knowledge and financial literacy, the prevalence of FI in the college student population is four times higher than the national average. The experience of FI may be accompanied by negative physiological and mental health outcomes, such as nutrient deficiencies, overweight or obesity, poor sleep, and increased stress, anxiety, and depressive symptoms, among others. With the emergence of FI as a public health concern, research in this field is limited, and populations of interest have predominately focused on children and older adults. Therefore, the objective of this dissertation was to explore the diet-related and cognitive outcomes of FI in a diverse population of university students using innovative biomarkers and novel technologies. This dissertation provides novel insight into the potential for strategic community-based interventions aimed at improving food security status and health outcomes in a population at increased risk for experiencing FI. The first aim of this dissertation was to validate assessment tools for identifying changes in diet-related biomarkers with the experience of FI. The Veggie Meter®, a device that implements pressure-mediated reflection spectroscopy to identify carotenoids in adipose, and Diet ID™, a novel image-based dietary assessment tool, were assessed against different biomarkers of dietary intake. After conducting a systematic review of existing literature (n = 29) comparing methods of reflection-spectroscopy against plasma carotenoids and/or validated tools for dietary intake, the Veggie Meter® produced moderate to strong correlations (average p = 0.76; p < 0.001), whereas other modes of spectroscopy were weakly correlated. Similarly, Diet ID™ was compared to other forms of dietary intake, including plasma carotenoids, skin carotenoids, and 24-hour NDSR dietary recalls in a diverse population of university students (n = 42). Diet ID™ was correlated to nearly all nutrients of interest, including macronutrients (diet quality, calories, carbohydrates, protein, fiber, and cholesterol), micronutrients (Vitamin A, calcium, folate, iron, sodium, potassium, Vitamins B2, B3, B6, C, and E), and phytonutrients (carotenoids). When compared to plasma carotenoids and skin carotenoid scores, controlling for BMI, carotenoid intake predicted by Diet ID™ was also correlated (Adjusted R2 = 0.37, p = 0.0001; Adjusted R2 = 0.41, p < 0.0001, respectively). Following validation of the Veggie Meter® and Diet ID™, these studies served as the impetus to use these assessment tools to evaluate the impact of food access resources on diet-related biomarkers as the second aim. This observational cohort study consisted of university students (n = 132) with varying food security statuses. Pre- and post-measurements of skin carotenoids, plasma carotenoids, and dietary carotenoids were collected to determine changes with the use of food access resources over the academic term. Food access resources were utilized an average of 3.1 ± 2.6 times. Criterion-validity between devices found significant associations between measures of plasma carotenoids, skin carotenoids, and dietary carotenoids. Of the biomarkers of interest, skin carotenoids were significantly higher from pre to post, accounting for the interaction of food security status and the frequency of food access resource usage (Adj R2 = 0.31; p = 0.001). Although this relationship was not observed for plasma carotenoids, or dietary carotenoids, this could be explained by the timing of resource usage. For dietary changes to be reflected in plasma, carotenoid-containing foods must have been consumed within approximately one week of post plasma collection. As only three participants out of the 132 utilized the resources during the final week of the study, changes in plasma carotenoids were not expected to reach significance. After exploring the physiological impacts of FI on diet-related biomarkers and the potential intervention strategies for improving these health-related biomarkers, further investigation into the cognitive impacts were of interest. The final aim was to explore the interrelationship between executive function (EF), food security status, and diet quality. Participants (n = 230) completed the CANTAB assessment to serve as an objective measure of EF, validated assessments for stress, along with other conditions that may impact cognition, and Diet ID™ to assess diet quality and nutrient intake. There were significant differences in mean scores for various domains of EF by food security status, such that impulsivity, poor decision making, and reduced planning capabilities were more present in individuals experiencing FI compared to their food secure peers (p < 0.05). The findings encompassed in this dissertation provides insight into the severity of physiological and cognitive outcomes associated with FI in the college student population. On-campus food access resources demonstrated promising effects on measurable health outcomes over the brief duration of a single academic term (< 10 weeks). These observed changes to diet and health-related biomarkers warrant the continued development of college and community-based resources aimed at alleviating the burden of food access, prioritizing foods that are nutrient-dense when possible. Future directions should seek to explore the longitudinal impacts of acute and chronic FI in the college student population to determine long-term ramifications to chronic disease risk.

Type 2 diabetes is increasing rapidly in the United States and Latin America and contributes significantly to the rise in health care spending. Diabetes increases the risk of cardiovascular disease, renal failure and blindness, and leads to other complications. Type 2 diabetes and its complications can be delayed in high-risk individuals through a healthy lifestyle and ongoing medical care. Some research suggests a relationship between diabetes and other underlying metabolic conditions, either as predisposing factors or as adverse outcomes of occupational exposures in farmworkers. UC Cooperative Extension can have a greater impact on the health and safety of California’s workforce by filling in research gaps and strengthening collaborations.

Scope

Methods and results

Conclusion

Background

Objectives

Methods

Results

Conclusions