Location: Food Components and Health Laboratory2012 Annual Report
1a. Objectives (from AD-416):
Objective 1: Elucidate factors which influence bioavailability, metabolism, and kinetics of dietary phytonutrients, such as anthocyanins, ellagitannins, flavonoids, allylic sulfides, and isoflavones, and define the observed inter-individual variation as well as the genetic basis for the observed variation. Sub-objective 1.A: Characterize effects of postharvest processing on phytonutrient content. Sub-objective 1.B.: Determine the importance of aglycone structure on anthocyanin bioavailability. Sub-objective 1.C.: Determine the importance of acylation on anthocyanin bioavailability. Sub-objective 1.D.: Determine the influence of protein on anthocyanin bioavailability. Sub-objective 1.E.: Identify metabolites of anthocyanins. Sub-objective 1.F.: Develop methods to isotopically label quercetin in leaf lettuce. Sub-objective 1.G.: Identify metabolites of quercetin. Sub-objective 1.H.: Develop methods to isotopically label isoflavones in soy. Objective 2: Determine the ability of plant-based dietary components to influence oxidative stress, inflammation, DNA damage, glucoregulation, and blood pressure, and define the inter-individual variation in these responses as well as the genetic basis for the variation. Sub-objective 2.A.: Determine the effect of pomegranate juice on blood pressure, endothelial function, and inflammation. Sub-objective 2.B.: Discover mechanisms by which garlic phytonutrients affect risk factors for cancer and cardiovascular disease.
1b. Approach (from AD-416):
Epidemiological studies have repeatedly shown that diets high in fruits and vegetables are associated with decreased risk of chronic diseases that ultimately strike most Americans. However, the scientific foundation necessary to translate these epidemiological findings into dietary recommendations is weak. Research is needed to clarify specific health benefits of phytonutrients, to determine their bioavailability, to delineate rates of metabolism and elimination from the body, and to identify genetic differences among individuals that impact phytonutrient action in the body. This plan describes a five-year research project to investigate content, bioavailability, metabolism, and health benefits of selected phytonutrients. Studies will be conducted to determine the effect of postharvest processing on phytonutrient content. The initial focus of the postharvest studies will be leaf lettuce and tomatoes, and these studies will be expanded to include kale, spinach, swiss chard, and strawberries as funding is available. Several studies will be conducted to improve understanding of phytonutrient bioavailability and metabolism. The proposed focus of these studies is anthocyanins, building on previous work in our lab. Methods will be developed to isotopically label quercetin in lettuce and isoflavones in soy. These studies will expand our isotopic labeling program from carotenoids and anthocyanins to other phytonutrients. The influence of phytonutrients on biomarkers of chronic disease will be investigated, with an initial focus on garlic due to its promising role in cancer prevention. Genotyping will be included in clinical studies whenever sufficient scientific justification exists. This research will be conducted through plant growth and postharvest studies, human feeding trials, quantitative and qualitative chemistry, molecular biology, and kinetic mathematical modeling techniques. Information generated from this project can be used to develop recommendations for dietary intakes of phytonutrients that will improve health and reduce risk of chronic disease.
3. Progress Report:
This is a project through which investigations into the health benefits of phytonutrients in humans are being conducted. The project has two primary components, one involving feeding agricultural products to humans to assess health impact and one involving investigation of environmental impacts on plant nutrients. Progress has been made on sample analyses on a human feeding study to identify potential role of low calorie cranberry juice in lowering risk factors for cardiovascular disease. Sample analyses was completed for the Cranberry Juice Heart Disease Prevention Study, a study in which 57 adult volunteers who consumed cranberry juice or placebo beverage for 8 weeks and provided blood and urine samples before and after the intervention. The completed analyses include lipids, lipoproteins, markers of inflammation, and cytokines. Cranberry juice intake lowered blood pressure, serum triglycerides (fat), and c-reactive protein (an inflammatory marker related to heart disease risk). ARS researchers at Beltsville, MD conducted a feeding study to determine how adaptation to grape polyphenols affects polyphenol bioavailability, and how this adaptation may be influenced by body mass index or tendencies toward metabolic syndrome. Fifteen adults, half of which were healthy with low BMI and half of which had high BMI and at least two risk factors for metabolic syndrome, consumed a grape polyphenol treatment. The grape polyphenol treatment consisted of grape seed extract capsules, resveratrol capsules, and Concord grape juice. The study showed that adaptation increased bioavailability of polyphenols, and that high BMI was associated with lower absorption of polyphenols. ARS researchers at Beltsville, MD completed analyses on a study of stomach acidity and anthocyanin absorption, since anthocyanins are most stable at acidic pH, and the stomach environment becomes less acidic with age. Anthocyanins and their metabolites were identified and quantified in blood after adults consumed berries with or without an agent to alter stomach acidity. Data interpretation is underway. Progress has been made on a study of garlic intake and mechanisms for cancer prevention. A global gene technique called microarray was used to obtain initial information about how garlic may affect gene expression (thus impacting metabolism). ARS researchers at Beltsville, MD used a follow-up technique called polymerase chain reaction to more robustly probe gene expression, and 7 genes were identified as sensitive to garlic intake. Data interpretation is underway. Progress has been made on sample analyses on a human feeding study to identify mechanisms of action of blackberries for prevention of cancer. A cutting edge technique called metabolomics, which broadly probes changes in metabolism, was used to demonstrate actions of blackberries on physiologic processes. Results suggested that blackberry intake affects fat metabolism. Results also suggested that bacteria in the large intestine, which is of increasing interest to the scientific and health communities, produce potentially active metabolites that enter the bloodstream.