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Scholarly Works (67 results)

  • Thesis
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UC Davis Electronic Theses and Dissertations (2021)

Atherosclerosis cardiovascular disease (ASCVD) is a complex, multifaceted condition that affects millions of adults; modifiable risk factors include weight, cholesterol, blood pressure and glucose control. Flavan-3-ols from cocoa and grapes and resveratrol from wine have been studied as strategies to improve vascular function, cholesterol, and glucose concentrations. Initiatives through the United States Department of Agriculture (USDA) have encouraged valorization of agricultural waste streams, such as wine production. The present study used Chardonnay grape marc (skins and seeds, also called pomace) blends, which builds upon the valorization efforts of the USDA yet also on the literature that phenolics provide a healthful addition to human diets. The purpose of this research was to determine whether results from previous animal trials that supplemented Chardonnay seed flour or Chardonnay seed extract, which identified improved cholesterol concentrations and glucose regulation, would translate to overweight, hyperlipidemic adult men and women. In addition, we were also interested in whether Chardonnay marc blends would impact gut hormones related to appetite control. The present study was a 16-week, randomized, double blinded crossover trial. We collected data from a total of 27 participants, where 24 individuals completed the full trial, and 3 individuals withdrew from the study. Participants were recruited based on criteria of having elevated lipids but non-medicated. This study supplemented proprietary formulations of a high Chardonnay seed extract and Chardonnay marc blend (HE), high Chardonnay marc and Chardonnay seed extract blend (HM) and a non-grape comparator of microcrystalline cellulose (MCC) for 3-weeks per intervention. Our first aim evaluated the impact of Chardonnay blends on ASCVD risk factors, specifically lipids and endothelial function. We concluded that there were no differences in fasting clinical lipid parameters of total cholesterol, low-density lipoprotein cholesterol (LDL-C), non-high density lipoprotein cholesterol (non-HDL-C) and triglycerides (TG). HDL-C was significantly lower following the HE intervention compared to both MCC and HM. Further NMR lipoprotein profiling revealed that the number of large HDL particles was significantly lower following HE compared to the MCC intervention. Postprandial triglyceride area under the curve was lower following the HM intervention compared to the HE intervention. There were no effects of the interventions on apolipoproteins AI, B, or CIII. Nor were there effects on oxidized LDL concentrations. Endothelial function, as measured by the finger plethysmography device EndoPat, was not affected by any of the interventions. The next aim investigated whether the Chardonnay blends would have an impact on glucose regulation. The results indicated that following the HM intervention, fasting glucose, and insulin decreased, in addition to indexes of insulin resistance and sensitivity compared to the MCC intervention were improved. There were no changes following the interventions in postprandial glucose or insulin response. The HM intervention also resulted in decreased concentrations of acute phase inflammation marker, serum amyloid A (SAA), compared to both MCC and HE interventions. However, this decreased SAA was not associated with the improved glycemic outcomes. The last aim explored the effects of the Chardonnay blends on gut hormones, ghrelin and peptide YY (PYY), as they related to appetite response. Here, we concluded that the HE blend decreased subjective ratings of hunger compared to MCC, despite the lack of changes in ghrelin concentrations, which signals hunger. In addition, following the HM supplementation, the concentrations of the hormone PYY, which signals satiation, was significantly higher compared to HE. No other subjective ratings of appetite were significant. This trial was the first to evaluate Chardonnay marc blends in numerous aspects of metabolism surrounding ASCVD. Phenolic compounds may not be the whole story when it comes to grape products and health potential. Our results indicate that the high marc blend has the potential to impact several risk factors and may be part of an overall strategy to reduce ASCVD risk. However, these are early results that should continue to be evaluated in future studies.

    Cover page: Metabolic Response of Chardonnay Grape Marc in Hyperlipidemic, Overweight and Obese Adult Men and Women
    • Thesis
    • Peer Reviewed
    UC Davis Electronic Theses and Dissertations (2023)

    Research on eating behavior is needed to improve our understanding of the complex factors that shape our diets and nutritional intakes, especially with the high prevalence of nutrition-related metabolic diseases and disordered eating. Among the various factors that influence eating behavior, the relationship between diet and appetite regulation is not fully understood. More data is needed on the interaction between dietary intake, appetite-related behaviors, and other biochemical and cognitive factors that have been shown to impact appetite and metabolism. The research presented in this dissertation aims to address this need by utilizing data from a cross-sectional nutritional phenotyping study of healthy adults. First, I examined the relationship between cognitive restraint and disinhibition with other food-related behaviors, and assessed the association of these behavior constructs with self-reported dietary intake. Results indicate that cognitive restraint was associated with food choice motivated by health, natural content, and ethical concern in the context of vegetable consumption and dietary quality in males, but not females. Next, I assessed whether subjective appetite response to a high-fat, high-sugar meal challenge was influenced by food rewards, eating behavior constructs, stress, or response of appetite-related hormones. The findings from this analysis suggest that an individual’s subjective appetite response was not biased by their liking or wanting of high-fat, sweet foods, nor by their appetite-related hormone responses and behaviors. Lastly, we identified various physiological, cognitive, and biochemical factors that characterized participants based on dairy food consumption. Participants that habitually consumed more than 2 cup equivalents of dairy foods per day were distinguished by higher daily caloric intake, lower response inhibition, and decreased ghrelin and lipid mediators. In all, these studies illuminate the complex relationship between diet and appetite regulation, as well as the need for comprehensive models of appetite to determine how key factors work together to modulate eating behavior.

      • Article
      • Peer Reviewed
      UC Davis Previously Published Works (2012)
      Abstract Background Established clinical tests are commonly used in disease diagnosis, but tools that enhance identification of metabolic dysfunctions are needed. This study was conducted to identify typical and atypical metabolite temporal patterns in response to paired meal challenge tests. Design Metabolic responses to high and low glycemic index (GI) meals were tested in 24 healthy pre-menopausal women, aged 20-50 y, with BMI of 25-30 kg/m2 using a cross-over design. On test days, blood glucose, insulin, leptin and non-esterified fatty acids were measured after an overnight fasting, and for 8 h following test meal consumption. The data were range scaled, and multivariate statistics were used to assess the presence of distinct response groups to the meal challenge tests. Results As expected, participants showed higher circulating glucose and insulin in response to the high GI compared to the low GI meal challenge. However, using range-scaling and Principal Component Analysis, three distinct groups were identified based on differential responses to the paired challenges. Members of the most populated group (n = 18) displayed little deviation from the expected response to the two meal challenges. Two minor groups (n = 3/group) with distinct responses were observed, one suggestive of sub-clinical insulin resistance, and the other suggestive of hyperleptinemia. Conclusions The differential responses of glucose, insulin and leptin to low and high glycemic test meals revealed three response groups. Dietary intervention studies traditionally evaluate group responses, and aim to identify the overall effect in the population studied. In contrast, our study analyzed the variance in the meal challenge responses, using an integrated physiological approach, rather than a reductionist approach. This phenotyping approach may be useful for detecting subclinical metabolic dysfunctions, and it could contribute to improved personalized nutrition management. This study is registered in ClinicalTrials.gov, record #200210295
        Cover page: Variation in metabolic responses to meal challenges differing in glycemic index in healthy women: Is it meaningful?
        • Article
        • Peer Reviewed
        UC Davis Previously Published Works (2018)
        Very little is known about how whole food diets, such as those based on the Dietary Guidelines for Americans (DGA), influence psychological stress and physiological stress load. To better understand the effects of whole food diets on stress, we examined in a randomized control trial the effects of a DGA-based diet on markers of psychological and physiological stress. A randomized, double-blind, controlled 8-week intervention was conducted in overweight and obese women randomly assigned to one of two diet groups: a diet based on the 2010 DGA or a diet based on a Typical American Diet (TAD). The Perceived Stress Scale and allostatic load were used to assess stress load. Eight-week change in perceived stress did not significantly (p = 0.45) differ between the DGA (+0.53 ± 0.99) and TAD (-0.57 ± 0.99) groups. Likewise, 8-week change in allostatic load did not significantly (p = 0.79) differ between the two diet intervention groups (DGA: +0.001 ± 0.26 vs. TAD: +0.105 ± 0.28). However, we did find strong inverse associations between 8-week change in stress and intervention-based improvements in diet quality (lower sodium and higher vegetable consumption). When statistically accounting for these inverse associations, we found that perceived stress and allostatic load were higher (p < 0.04) in the DGA group. These findings suggest that improvements in dietary vegetable and sodium intake mediated effects of the diet intervention on psychological and physiological stress load. That is, adopting and adhering to a diet of higher quality (DGA) for 8 weeks may have been generally more stressful in the absence of improvements in vegetable or sodium consumption. This study provides further evidence for the mental health benefits of maximizing vegetable and minimizing sodium consumption.
          Cover page: Diet Quality for Sodium and Vegetables Mediate Effects of Whole Food Diets on 8-Week Changes in Stress Load
          • Article
          • Peer Reviewed
          UC Davis Previously Published Works (2022)

          Background

          Diet and cortisol are independently linked to cardiometabolic function and health, but underlying alterations in circulating cortisol may influence beneficial cardiometabolic effects of consuming a healthy diet.

          Objective

          This study was a secondary analysis to examine whether baseline concentrations of waking salivary cortisol interacted with 8-wk whole-food diet interventions to affect cardiometabolic outcomes.

          Methods

          A randomized, double-blind, controlled 8-wk diet intervention was conducted in 44 participants. The trial was conducted at the Western Human Nutrition Research Center in Davis, California. Participants were overweight or obese women aged 20-64 y, minimally active, and insulin resistant and/or dyslipidemic. Diets were randomly assigned and based on the 2010 Dietary Guidelines for Americans (DGA) or a typical American diet (TAD). Cardiometabolic risk factors and salivary cortisol were assessed at baseline and at 8 wk. Primary outcome measures included 8-wk change in overnight fasted cardiometabolic risk factors, including blood pressure, BMI, and circulating triglycerides, cholesterol, glycated hemoglobin (HbA1c), nonesterified fatty acids, and high-sensitivity C-reactive protein. This trial was approved by the University of California, Davis, Institutional Review Board.

          Results

          Baseline waking cortisol concentrations interacted (P = 0.0474) with diet to affect 8-wk changes in fasting total cholesterol. Compared with a TAD, a DGA diet was associated with 8-wk decreases in total cholesterol in participants with low (10th percentile of all participants; 2.76 nmol/L) or average (7.76 nmol/L) but not higher (90th percentile of all participants; 13.44 nmol/L) baseline waking cortisol. Consistent with this finding, there was a DGA-specific positive association (P = 0.0047; b: 2.88 ± 0.94) between baseline waking cortisol and 8-wk increases in total cholesterol.

          Conclusions

          The underlying status of waking cortisol may explain interindividual variability in total cholesterol responses to whole-food diets. This trial was registered at www.clinicaltrials.gov (https://clinicaltrials.gov/ct2/show/NCT02298725) as NCT02298725.
            Cover page: Waking Salivary Cortisol Associated with Magnitude of Cholesterol Reduction in Women Fed a Healthy Whole-Food Diet for 8 Weeks
            • Article
            • Peer Reviewed
            UC Davis Previously Published Works (2019)
            It is largely unknown whether and how whole food diets influence psychological stress and stress system responsiveness. To better understand the effects of whole diets on stress system responsiveness, we examined randomized control trial effects of a whole food diet based on the Dietary Guidelines for Americans (DGA) on cortisol responsiveness. A randomized, double-blind, controlled 8-week intervention was conducted in overweight and obese women to examine differentiated effects between two diet intervention groups: one based on the 2010 DGA and the other one based on a typical American diet (TAD). During a test week that occurred at baseline and again after 8 weeks of the intervention, we assessed salivary cortisol collected at 14 selected times across the day, including upon awakening, at bedtime, and during a test visit, and administered a standardized social stress task (Trier Social Stress Test, TSST). There were no statistical differences between the diet groups in salivary cortisol at baseline or after 8 weeks. However, when considering differences in dietary carbohydrate, but not fat or protein, from the pre-intervention (habitual) to the intervention period, there was a significant (P = 0.0001) interaction between diet group, intervention week, saliva sample, and level of intervention-based change in carbohydrate consumption. This interaction was reflected primarily by an 8-week reduction in salivary cortisol during a period just prior to (log Δ -0.35 ± 0.12 nmol/L) and 30 (log Δ -0.49 ± 0.12 nmol/L), 60 (log Δ -0.50 ± 0.13 nmol/L), 90 (log Δ -0.51 ± 0.13 nmol/L), and 120 (log Δ -0.4476 ± 0.1231 nmol/L) min after the TSST in the DGA group having the highest increase (90th percentile) in carbohydrate consumption. In support of this finding, we also found significant (P < 0.05) and inverse linear associations between dietary carbohydrate and log salivary cortisol, with the strongest negative association (β: -0.004 ± 0.0015, P = 0.009) occurring at 30 min post-TSST, but only in the DGA group and at week 9 of the intervention. Together, increasing dietary carbohydrate as part of a DGA-based diet may reduce circulating cortisol and dampen psychological stress-related cortisol responsiveness.
              Cover page: Increasing Dietary Carbohydrate as Part of a Healthy Whole Food Diet Intervention Dampens Eight Week Changes in Salivary Cortisol and Cortisol Responsiveness
              • Article
              • Peer Reviewed
              UC Davis Previously Published Works (2003)
                Cover page: Reply to TJ Vasankari
                • Article
                • Peer Reviewed
                UC Davis Previously Published Works (2019)
                The gut microbiota is increasingly implicated in the health and metabolism of its human host. The host's diet is a major component influencing the composition and function of the gut microbiota, and mounting evidence suggests that the composition and function of the gut microbiota influence the host's metabolic response to diet. This effect of the gut microbiota on personalized dietary response is a growing focus of precision nutrition research and may inform the effort to tailor dietary advice to the individual. Because the gut microbiota has been shown to be malleable to some extent, it may also allow for therapeutic alterations of the gut microbiota in order to alter response to certain dietary components. This article is the second in a 2-part review of the current research in the field of precision nutrition incorporating the gut microbiota into studies investigating interindividual variability in response to diet. Part I reviews the methods used by researchers to design and carry out such studies as well as analyze the results subsequently obtained. Part II reviews the findings of these studies and discusses the gaps in our current knowledge and directions for future research. The studies reviewed provide the current understanding in this field of research and a foundation from which we may build, utilizing and expanding upon the methods and results they present to inform future studies.
                  Cover page: The Role of the Gut Microbiome in Predicting Response to Diet and the Development of Precision Nutrition Models. Part II: Results.
                  • Article
                  • Peer Reviewed
                  UC Davis Previously Published Works (2002)
                  This review explores whether fructose consumption might be a contributing factor to the development of obesity and the accompanying metabolic abnormalities observed in the insulin resistance syndrome. The per capita disappearance data for fructose from the combined consumption of sucrose and high-fructose corn syrup have increased by 26%, from 64 g/d in 1970 to 81 g/d in 1997. Both plasma insulin and leptin act in the central nervous system in the long-term regulation of energy homeostasis. Because fructose does not stimulate insulin secretion from pancreatic beta cells, the consumption of foods and beverages containing fructose produces smaller postprandial insulin excursions than does consumption of glucose-containing carbohydrate. Because leptin production is regulated by insulin responses to meals, fructose consumption also reduces circulating leptin concentrations. The combined effects of lowered circulating leptin and insulin in individuals who consume diets that are high in dietary fructose could therefore increase the likelihood of weight gain and its associated metabolic sequelae. In addition, fructose, compared with glucose, is preferentially metabolized to lipid in the liver. Fructose consumption induces insulin resistance, impaired glucose tolerance, hyperinsulinemia, hypertriacylglycerolemia, and hypertension in animal models. The data in humans are less clear. Although there are existing data on the metabolic and endocrine effects of dietary fructose that suggest that increased consumption of fructose may be detrimental in terms of body weight and adiposity and the metabolic indexes associated with the insulin resistance syndrome, much more research is needed to fully understand the metabolic effect of dietary fructose in humans.
                    Cover page: Fructose, weight gain, and the insulin resistance syndrome 1 , 2 , 3
                    • Article
                    • Peer Reviewed
                    UC Davis Previously Published Works (2013)

                    Background

                    Currently, no simplified approach to estimating food costs exists for a large, nationally representative sample.

                    Objective

                    The objective was to compare 2 approaches for estimating individual daily diet costs in a population of low-income women in California.

                    Design

                    Cost estimates based on time-intensive method 1 (three 24-h recalls and associated food prices on receipts) were compared with estimates made by using less intensive method 2 [a food-frequency questionnaire (FFQ) and store prices]. Low-income participants (n = 121) of USDA nutrition programs were recruited. Mean daily diet costs, both unadjusted and adjusted for energy, were compared by using Pearson correlation coefficients and the Bland-Altman 95% limits of agreement between methods.

                    Results

                    Energy and nutrient intakes derived by the 2 methods were comparable; where differences occurred, the FFQ (method 2) provided higher nutrient values than did the 24-h recall (method 1). The crude daily diet cost was $6.32 by the 24-h recall method and $5.93 by the FFQ method (P = 0.221). The energy-adjusted diet cost was $6.65 by the 24-h recall method and $5.98 by the FFQ method (P < 0.001).

                    Conclusions

                    Although the agreement between methods was weaker than expected, both approaches may be useful. Additional research is needed to further refine a large national survey approach (method 2) to estimate daily dietary costs with the use of this minimal time-intensive method for the participant and moderate time-intensive method for the researcher.
                      Cover page: Estimating dietary costs of low-income women in California: a comparison of 2 approaches 1 , 2 , 3
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