1a. Objectives (from AD-416)
1. Using an epidemiologic approach, investigate the role of whole grains, selected nutrients, other bioactive food components, and healthy dietary patterns in preventing age-related development of metabolic risk factors for type 2 diabetes mellitus, cardiovascular disease, cancer and musculoskeletal disorders. 2. Determine the validity of biomarkers for whole grain intake, their use in assessing relationships between whole grains intake and disease risk, and the relationship between these biomarkers and insulin resistance phenotypes. 3. Using an epidemiologic approach, examine determinants of adherence to the recommended dietary patterns in the Dietary Guidelines for Americans (DGA) and the relation between adherence to these patterns and prevention of age-related weight gain, abdominal obesity, and related metabolic disorders such as inflammation, endothelial dysfunction and insulin resistance. 4. Using an epidemiologic approach, investigate safe upper limits for the dietary intake of folic acid. 5. Using an epidemiologic approach, determine relationships between B-vitamin status, homocysteine levels, genetic mutations and the prevention of age-related cognitive decline in humans. 6. Using an epidemiologic approach, examine the relationships between vitamin D and fatty acid intakes and age-related eye diseases, including cataract and maculopathy.
1b. Approach (from AD-416)
Many age-related conditions, such as cardiovascular disease, diabetes, dementia, cancer, musculoskeletal disorders and age-related eye disease, appear to have strong nutritional components. Improved nutrition through public health recommendations and interventions could have a tremendous impact on the economic and societal costs associated with these disabilities, but development of recommendations and interventions requires a greater understanding of the presumptive role that nutrition plays in delaying the onset of disease and disability. Epidemiologic methods applied to community-based investigations of aging populations provide a valuable tool to help meet this need. We will use these methods to address project objectives.
3. Progress Report
Our research on nutrition and risk of obesity and chronic disease (Objective 1) included projects related to obesity, insulin resistance, metabolic syndrome, diabetes, and cardiovascular disease. As part of our research on weight gain and obesity, we showed that whole-grain and cereal fiber intakes were inversely related to percent total body and trunk fat mass and that better adherence to a Mediterranean diet was associated with a lower incidence of abdominal obesity. As part of our research on diet and metabolic risk, we observed that higher vitamin D status was associated with a lower risk of insulin resistance and diabetes and better adherence to a Mediterranean diet was associated with a lower incidence of metabolic syndrome and insulin resistance. As part of our research on diet and cardiovascular disease, we showed that a high glycemic index diet unfavorably affects triglycerides and HDL cholesterol, and that vitamin B6 status was inversely related to inflammation, an important cardiovascular disease risk factor. We completed the update of our food frequency flavonoid database for our project on flavonoid intake and cardiovascular disease risk and completed most of the statistical analyses for our project on plant-based diets, diet quality and cardiovascular disease risk. As part of our work of identifying biomarkers whole grain consumption (Objective 2), we measured blood alkylresorcinol levels. Alkylresorcinols are unique chemicals found in whole wheat and rye and are believed to be a potentially useful objective and quantitative marker of whole wheat consumption. These biomarkers will ultimately help determine consumption of whole grains by Americans. As part of our research on the Dietary Guidelines for Americans (DGA) (Objective 3), we showed that that better adherence to 2005 DGA is associated with a reduced progression of coronary artery atherosclerosis in women. This demonstrates that adherence the 2005 DGA is associated with a reduce risk of disease progression. As part of our research on safe upper limits of folic acid (Objective 4), we showed that unmetabolized folic acid, the synthetic form of the vitamin folate found in vitamin supplements and fortified foods, was detected in 50% of older Americans with folic acid intakes above 585 micrograms/day. We also showed that among older Americans with inadequate vitamin B12 status, the presence of circulating unmetabolized folic acid was related to lower scores on cognitive tests. This accomplishment helps us to better understand the basis for folic acid recommendations. As part of our research on B vitamins and cognitive function (Objective 5), we have completed recruitment and initiated baseline laboratory analyses. This accomplishment will help us understand the role of nutrition in age-related cognitive decline. For publications related to this project, see parent project #1950-51530-009-00D.
1. Whole-Grain Intake and Cereal Fiber Are Associated with Lower Abdominal Adiposity. Foods high in dietary fiber may play an important role in regulating body weight. Few observational studies have examined the relationship between dietary fiber from different sources and body fat. ARS-funded researchers from Tufts University in Boston, MA examined the relation between grain intake (whole and refined), and measures of body fat. They observed that higher whole-grain and cereal fiber intakes were associated with a lower body mass index (a higher body mass index is a marker of overweight), percent total body fat, and percent trunk fat mass (trunk fat is a surrogate measure for abdominal fat mass, which is more strongly associated with risk of metabolic disorders than other fat depots). This research suggests that higher intakes of cereal fiber, particularly from whole-grain sources, may be one means of limiting body fat mass, particularly in the abdominal region.
2. Plasma 25-Hydroxyvitamin D Is Associated with Insulin Resistance in Nondiabetic Adults. Insulin resistance is the main defect that characterizes the development of type 2 diabetes, but there is little information on the relationship between vitamin D status and insulin resistance. To advance our understanding of the role of vitamin D status in the development of insulin resistance, ARS-funded researchers from Tufts University in Boston, MA examined the association between insulin resistance and plasma vitamin D levels. They observed that individuals with higher plasma vitamin D concentrations had less insulin resistance. These results suggest that maintaining optimal vitamin D status might be important for the prevention of type 2 diabetes.
3. Mediterranean-Style Dietary Pattern is Associated with a Reduced Risk of Metabolic Syndrome Traits and Incidence. There is evidence of the benefit of the Mediterranean-style dietary pattern on disease risk in Mediterranean countries, but the health benefits of consuming a Mediterranean-style dietary pattern based on foods available in the American diet has not been demonstrated. Therefore, ARS-funded researchers from Tufts University in Boston, MA examined the relation between consumption of a Mediterranean-style dietary pattern and insulin resistance, metabolic syndrome and its component risk factors (larger waist circumference, elevated blood glucose and triglyceride levels, and hypertension, and low HDL-cholesterol) in a population-based sample of adult Americans. They observed that individuals whose diets had greater conformity to the Mediterranean-style dietary pattern had smaller increases in waist circumference, blood glucose and triglyceride levels, and greater increases in HDL-cholesterol; were less likely to develop insulin resistance; and had a lower incidence of metabolic syndrome. These findings suggest that consumption of a diet consistent with the principles of the Mediterranean-style diet may be protective against developing metabolic syndrome, a potent risk factor for both diabetes and cardiovascular disease risk, in an American population.