2012 Annual Report
1a.Objectives (from AD-416):
Objective 1: Investigate macronutrient modulation of biomarkers of chronic disease.
Sub-objective 1.A.: Investigate the role of individual fatty acids (such as alphalinolenic, stearic, conjugated linoleic, and/or vaccenic acids) on markers of inflammation and oxidation related to chronic disease. Delineate their metabolic pathways.
Sub-objective 1.B.: Determine the differential effects of protein sources and
macronutrient profiles on post-prandial oxidation, oxidative stress, insulin signaling,and blood pressure regulation.
Objective 2: Improve biomarkers and indicators of nutritional adequacy through investigation of micronutrient metabolism.
Sub-objective 2.A.: Investigate the differential in vivo metabolism of various forms of micronutrients (such as tocopherol and/or folate) through mathematical modeling.
1b.Approach (from AD-416):
Appropriate macro- and micronutrient intake is fundamental to a diet that will maintain health and reduce risk of chronic, degenerative diseases. For many nutrients or classes of nutrients, qualitative and quantitative estimates of intake to maintain health are available. However, for other nutrients, where there are a variety of dietary sources, specific sources may offer additional health benefits as compared to others. Many observations of the health effects of specific sources of food are based on epidemiologic data and therefore do not provide an opportunity to show a cause and effect. For example, epidemiologic data suggest that there is no association between consumption of naturally occurring trans fatty acids and risk for coronary heart disease whereas trans fatty acids from partially hydrogenated vegetable sources do increase risk for coronary heart disease and death. Epidemiologic data suggest that a decrease in body weight is associated with low-fat dairy food consumption but identification of the specific component(s) (such as proteins) found in low-fat dairy foods that may be responsible for this effect is needed. This five-year project will investigate the effects of different sources of trans fatty acids and protein on risk factors associated with cardiovascular disease, and diabetes in humans and will assess the relative bioavailability of synthetic and natural sources of vitamin E in humans using mathematical modeling. This research will fill knowledge gaps in macro and micronutrient metabolism and provide a scientific basis for dietary recommendations and nutrition policy.
Using a novel dietary design, scientists were able to measure the calorie value of almonds while they were fed as part of a mixed diet. Results from this study revealed that the current methods for estimating calories of almonds overestimates their actual calorie amount by up to 32%. These results suggest that the current methods used for calculating the calorie content of food may introduce significant error in calculating the energy value of some foods.
Research continues on a study of vitamin E requirement in order to improve scientific basis for dietary guidelines. The dietary recommendation for vitamin E is based on sparse data and a loose association between the purported function of vitamin E in the body and a test meant to reflect a small portion of that function. A study was conducted in which adults consumed a specially tagged form of vitamin E that could be followed through to body for months. Blood, urine, and feces were analyzed for the specially tagged vitamin E. ARS researchers used a mathematical technique called kinetic modeling to determine that target blood values for vitamin E can be maintained with a daily intake much lower than the current recommended daily allowance (RDA). This information is expected to have a substantial impact of future dietary intake recommendations.
Advanced glycation end-products (AGEs) are compounds that occur in food when the food is browned or cooked at high temperatures. These advanced glycation end-products are thought to increase risk for a number of chronic diseases. For this study, ARS researchers provided a controlled diet to adult volunteers. Researchers collected blood and urine samples before the intervention, and analysis of these samples is currently underway.
A human feeding study was conducted to investigate the role of avocados in improving heart health. Avocados are expected to provide benefit by promoting healthy blood vessels. Researchers provided sixty volunteers with controlled diets, one diet being comprised of typical American foods, and the other diet containing avocado in place of foods high in saturated fat. At the beginning and end of the intervention, blood and urine were collected for analysis of markers of cardiovascular disease. ARS researchers also administered a specialized blood pressure test to determine potential improvements in the ability of blood vessels to relax when necessary, thus maintaining healthy blood pressure.
A study was initiated that examines the interaction of the consumption of meals containing predominantly fat, carbohydrate, or protein following either high intensity/short duration or low intensity/long duration exercise interventions. This study also provides continuous real time data on glucose and substrate oxidation levels needed for the development of mathematical models to predict substrate utilization. In addition, data collection was completed for studies that examine the impact of a diet and exercise intervention on glucose regulation and whole body carbohydrate, fat, and protein oxidation in both young and elderly men and women.
Dietary requirement for vitamin E. The dietary requirement for vitamin E is based on sparse data related to how much vitamin E must be consumed to provide a blood level that will protect red blood cells from hydrogen peroxide damage in a laboratory test. However, this blood assay of vitamin E function that is not necessarily tightly associated with actual vitamin E need. Using several cutting edge technologies related to specially tagging vitamin E, administering that tagged vitamin E to humans, measuring that vitamin E with extremely specialized equipment, and analyzing the data with mathematics, we determined that the target blood values for vitamin E can be maintained with a daily intake much lower than the current recommended daily allowance (RDA). This information is expected to have a substantial impact of future dietary intake recommendations.
Accurate assessment of the calorie content of foods. The calorie content of foods is generally based on methods and data that are over 100 years old. In order to overcome limitations of the current methods and data, using a novel dietary design, the calorie content of almonds and pistachios when fed as part of a mixed diet has been empirically measured for the first time. The results show that the current methods for estimating the calorie content of almonds, as required for food labeling, overestimate the actual measured calorie content by up to 32%. These findings are consistent with other data on nut consumption and maintenance of a healthy body weight, as discussed in the Dietary Guidelines.
Mai, V., Ukhanova, M., Baer, D.J. 2010. Understanding the extent and sources of variation in gut microbiota; a prerequisite for establishing associations with disease. Diversity. 2:1085-1096.
Baer, D.J. 2012. What do we really know about the health effects of natural sources of trans fatty acids? American Journal of Clinical Nutrition. 95:267-268.
Gebauer, S.K., Chardigny, J., Proctor, S.D., Jacobsen, M.U., Lamarche, B., Lock, A.L., Baer, D.J. 2011. Effects of ruminant trans fatty acids on cardiovascular disease and cancer: a comprehensive review of epidemiological, clinical, and mechanistic studies. Advances in Nutrition. 2:332-354.