Location: Food Components and Health Laboratory
2024 Annual Report
Objectives
Objective 1: Determine the genotype, phenotype and food matrix factors that influence absorption, distribution, metabolism or excretion of glucosinolates, phenolics, and other food components.
Objective 2: Determine how consumption of foods and food components, including but not limited to glucosinolates, phenolics, and carotenoids, modulate inflammatory and metabolic pathways that affect risk for cardiovascular diseases, diabetes, cancer, and other chronic disease.
Approach
U.S. agriculture provides us with myriad dietary components that can have a significant impact on health. The human diet contains thousands of bioactive food components which have a multitude of physiologic actions, some of which can interrupt processes in the development of a host of chronic diseases. The goal of this project plan is to enhance the understanding of physiologic actions of diet-based bioactive compounds to improve their absorption and efficacy in promoting health and preventing disease. We have organized this project to address current and emerging nutrition issues while capitalizing on the experience and expertise of the research team assigned to this project. We will address the following factors for several different categories of food components and bioactives: how much of a dietary component we absorb from the food, how well we retain and utilize that dietary component, and how the bioactive compounds function in the body (mechanisms of action) to prevent the most significant modifiable health risks faced by American adults, including cardiovascular disease, diabetes, and cancer. Bioactive compounds will include polyphenols, carotenoids, and sulfur compounds from Brassica vegetables, because all demonstrate promising health benefits, and work with these compounds capitalizes on previous progress in our laboratory.
Progress Report
This is the final report is for project 8040-51000-059-000D entitled "Absorption, Distribution, Metabolism, and Excretion of Food Components and their Impact on Chronic Disease Risk." The project contributes to National Program 107 and focuses on Component 1 (Linking Agricultural Practices and Beneficial Health Outcomes), Component 3 (Scientific Basis for Dietary Guidance), and Component 4 (Prevention of Obesity and Obesity-Related Diseases) through human studies focusing on Brassica vegetables, whole grains, and berries.
During the five-year span of this project, multiple human dietary intervention studies were completed. The studies included interventions with a number of different foods, and included shorter-term feeding studies to evaluate nutrient metabolism, and longer-term feeding studies to assess health outcomes.
For Objective 1, a study of whole grains (oats and wheat) was completed to investigate how the processing of grains impacts the absorption, distribution, metabolism, and excretion of phenolics (5-n-alkylresorcinols, avenanthramides, saponins) found in whole grains. Biospecimens were analyzed to determine the concentration of phenolics in blood after consumption of oats and wheat as well as bacterial metabolites from isolated from fecal samples. Some bacterial metabolites appear in the blood longer than the parent compounds, and these compounds may be useful as markers of oat intake especially for assessing medium- to long-term consumption oat intake.
Also for Objective 1, the absorption, distribution, metabolism, and excretion of vitamin D in pregnant women was studied in collaboration with scientists at Cornell University. During pregnancy, the blood pool of the active form of vitamin D increases throughout most of the pregnancy period. Why or how this phenomenon occurs is unknown, but it likely represents an important adaptation to the growing child's health. A new lab method was developed to measure the amount of the isotopically labeled vitamin forms in blood after a tracer dose. It was found that the women in the study had marked variability in their vitamin D metabolism and that a protein called "vitamin D binding protein" had the greatest influence on the vitamin D metabolism. The new method developed in this work will allow further studies of vitamin D metabolism in various populations, including pregnant and nonpregnant women.
Several studies with Brassica vegetables were completed (Objective 1). These studies focus phenotype and food matrix factors that influence the absorption, distribution, metabolism or excretion of glucosinolates. Studies were conducted with kale and broccoli, including different food preparation methods of broccoli representing different food matrices.
A study of the healthfulness of kale, a vegetable that has been increasing in popularity over the past decade, was completed. The dietary intervention with humans was conducted to identify the effects of kale consumption on xenobiotic metabolizing enzymes, to identify novel metabolites of indole glucosinolates in human blood and urine after consumption of kale, and to determine if kale consumption results in upregulation of myrosinase (an enzyme important for the conversion of kale glucosinolates into bioactive compounds) producing bacteria in the colon resulting in greater appearance of glucosinolate metabolites in blood and urine. It was found that consuming baby kale modifies detoxifying enzymes, reducing cancer risk. Xenobiotic metabolizing enzymes process (and detoxify) exogenous and endogenous metabolites, including procarcinogens, and prepares them for excretion from the body, thereby decreasing the risk of cancer. Further, conjugated bilirubin (used to remove compounds from the body) was reduced when kale was included in the diet. The implications of these results for cancer risk will be clarified as the functions of xenobiotic metabolizing enzymes become better understood.
Another study was conducted to improve understanding of the links between brassica vegetable consumption, and broccoli in particular, and cancer risk. A human feeding intervention was conducted to determine, using advanced non-targeted targeted metabolomic approaches, if metabolites of certain compounds from broccoli can be used as markers of broccoli consumption. Glucosinolate and indole metabolites were identified in blood and urine, including the identification of indole metabolites not previously reported in the scientific literature. The results of this research suggest that glucoraphanin and indole metabolites may serve as marker compounds for the intake of broccoli in people. Additionally, it was found that broccoli consumption modifies gut microbes in lean people. Cruciferous vegetables are a good source of dietary fiber and bioactives, and can be metabolized by gut microbes, which are increasingly linked to improved health outcomes. Broccoli consumption changed the kinds of microbes in the gut, and affected processes related to energy metabolism. The effects of broccoli consumption were most pronounced in lean people.
In addition, a study of broccoli snacks was conducted. Vegetable snack foods are becoming increasingly popular but little research has been done to investigate the effect of processing of vegetables on their bioactive compounds. Methods were developed for in-house preparation of the broccoli (freeze drying and roasting). The research protocol was developed, institutional review board approval was obtained, and the clinical trial was completed. Laboratory analyses were initiated. Isothiocyanates from freeze-dried broccoli were well-absorbed into the blood stream by study volunteers. In addition, oven-roasted broccoli that was later freeze-dried also provided absorbable isothiocyanates, though absorption was greatly increased when daikon radish was added as a source of extra myrosinase.
For Objective 2, analysis of data from a dietary intervention study of berries was completed. Specifically, investigations at the mitochondrial level were analyzed to determine how berry and berry components might alter critical energy metabolism pathways at the cellular level. Differences were observed in multiple respiration states of mitochondria with the greatest differences being between the food preparations with high berry pigments verses high fiber. These results confirm the influence of berry treatments on bioenergetics in humans. Effects appear to be different for different berry components, and differ between the fasted and fed state. This research identifies how changes in metabolism at the cellular level might explain some of the bodyweight-related changes that have been observed following berry consumption. Complementary studies with cells were conducted to characterize the effect of purified cyanidin-3-glucoside or a blackberry extract on cellular metabolism and mitochondrial number in 3T3-L1 adipocyte (“fat”) cells to explore potential mechanisms, and cellular oxygen consumption was found to increase when exposed to berry extract or purified cyanidin-3-glucoside.
Additional research with berries (Objective 2) showed that berry consumption in humans improves insulin response. This study was initiated to determine if insulin sensitivity (related to blood sugar metabolism) is improved by consuming whole mixed berries (blackberries, blueberries, cranberries, raspberries, and strawberries), mixed berry juice, or fiber. Berries contain several compounds, such as flavonoids and fiber, that may have beneficial effects on insulin sensitivity and blood sugar regulation, possibly reducing risk for type 2 diabetes. The berry preparations resulted in a lower serum insulin area under the curve. This result suggests the potential for mixed berry preparations to improve post-prandial insulin response, and perhaps reduce risk for diabetes.
To support progress for Objective 2, a study to measure the metabolizable energy value of pulses was completed. This study builds on previous research that focused on the metabolizable energy value of tree nuts. In studies of tree nuts, metabolizable energy value of tree nuts was found to be up to 25% less than values predicted by the standard calculation method using Atwater factors. This discrepancy is related to limited data and incorrect assumptions used in the methods for calculating the metabolizable energy value of tree nuts. For chickpeas and lentils, this research has shown that the Atwater calculation method for these two foods also overestimates the energy (calories) in these foods.
Also in support of Objective 2, research was conducted to better understand the link between flavan-3-ol consumption and reduction of risk for heart disease and type 2 diabetes. Flavan-3-ols are a class of naturally occurring polyphenolic compounds found primarily in tea and cocoa whose consumption has been associated with reduced cardiometabolic risk which includes outcomes (including death) from coronary heart disease, stroke, hypertension, and type 2 diabetes. A systematic review and meta-analysis of published research studies was conducted to determine if there is consistent evidence that higher flavan-3-ol intake, irrespective of dietary source, reduces cardiometabolic risk. After careful identification of the studies and evaluation of their quality, in studies using good methodologies there are improvements in markers of risk including cholesterol, blood pressure, insulin sensitivity. Further, there is moderate evidence flavan-3-ol and monomer intakes were associated with reduced risk of cardiovascular disease, coronary heart disease, stroke and type 2 diabetes. Available evidence supports a beneficial effect of flavan-3-ol intake on cardiometabolic outcomes, and this research has been used to develop intake guidance for flavan-3-ols in food.
Accomplishments
1. Objective biomarkers to assess food intake were developed. The discovery, development, and use of biomarkers of food intake are needed to help establish the links between diet and health. Historical methods using memory fall short. ARS researchers at the Beltsville Human Nutrition Research Center, Beltsville, Maryland, along with collaborators at the University of Illinois, used artificial language approaches to identify fecal genes and genomes that accurately predict food intake. The researchers found that there is high predictive accuracy to using these approaches for the foods studied (vegetables and nuts). These findings reveal the promise of metagenomics in establishing fecal bacterial genes as biomarkers of food intake to objectively complement self-reported food measures.
Review Publications
Jetton TL, Galbraith OT, Peshavaria M, Bonney EA, Holmen BA, Fukagawa NK. Sex-specific metabolic adaptations from in utero exposure to particulate matter derived from combustion of petrodiesel and biodiesel fuels. Chemosphere 346 (2024) 140480. Online 23 October 2023. https://doi.org/10.1016/j.chemosphere.2023.140480.
Shinn, L.M., Mansharamani, A., Baer, D.J., Novotny, J., Charron, C.S., Kahn, N.A., Zhu, R., Holscher, H.D. 2024. Fecal metagenomics to identify biomarkers of food intake in healthy adults: findings from randomized, controlled, nutrition trials. Journal of Nutrition. 154:271-283.
Whent, M.M., Huang, J., Childs, H., Slavin, M., Harrison, D.J., Novotny Dura, J., Yu, L., Pehrsson, P.R., Wu, X. 2023. Stability of carotenoids in sweet corn: Part 2. Effects of blanching, freezing, and canning. ACS Food Science and Technology. 3(9):1590-1599. https://doi.org/10.1021/acsfoodscitech.3c00273.
Chuang, J.C., Clifford, A.J., Kim, S., Fadel, J.G., Novotny, J., Kelly, P.B., Holstege, D.M., Walzem, R.L. 2024. Separation of lipoproteins for quantitative analysis of 14C-labeled lipid soluble compounds by accelerator mass spectrometry. International Journal of Molecular Sciences. 25(3):1856. https://doi.org/10.3390/ijms25031856.