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 the development of age-related conditions such as type 2 diabetes mellitus, cardiovascular disease, cancer, musculoskeletal disorders and age-related eye disease. 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, investigate the role of nutritional factors in limiting the cormorbidities such as CVD and premature mortality in individuals with chronic kidney disease (CKD).
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, inflammation, diabetes, and CVD. As part of our research on weight gain and obesity, we showed that whole-grain intake was inversely associated with visceral adiposity, but that increasing consumption of refined grain appeared to negate the protective association between whole grains and visceral adiposity. As part of our research on diet and metabolic risk, we observed that an index reflecting higher vitamin D status was associated with a lower incidence of type 2 diabetes. Preliminary findings from our research on flavonoid intake and inflammation suggest that higher intakes of two subclasses of flavonoids, the flavonols and anthocyanidins, were associated with less inflammation. As part of our research on diet and CVD, we showed that a higher level of circulating homocysteine, a blood marker indicating lower vitamin B12 and folate status, was associated with increased risk of plaque formation in the carotid artery. Our progress on characterizing the role of nutrition in risk of age-related disease is crucial in identifying potential interventions aimed at maintaining health as we age. As part of our work of identifying biomarkers whole grain consumption (Objective 2), we measured blood alkylresorcinol levels in a group of healthy elderly individuals. Alkylresorcinols are unique chemicals found in whole wheat and rye and are believed to be useful as a marker of whole wheat consumption. In preliminary analyses based on theses alkylresorcinol levels, we demonstrated that they correlated well with self-reported whole grain intake and were inversely associated with BMI in healthy older adults, confirming observational data showing higher whole grain intake is associated with lower BMI. We also initiated a whole wheat metabolic feeding study to determine the dose relationship between whole wheat consumption and circulating alkylresorcinol levels. Use of biomarkers, like alkylresorcinols, will ultimately help us to better characterize consumption of whole grains by Americans, and consequently, help us to better understand the benefits of whole grains on healthy aging. As part of our research on B vitamins and cognitive function (Objective 5), we have stopped follow-up cognitive testing for our B vitamin intervention study, which is designed to examine the hypothesis that B vitamin supplementation is associated with less age-related cognitive decline, due to the premature termination of the parent trial on which our ancillary cognitive study was based. Our accomplishments related to this objective will help us understand the role of nutrition in preventing age-related cognitive decline. As part of our new objective (objective 6) on the role of nutritional factors in limiting the co-morbidities such as CVD and premature mortality in individuals with chronic kidney disease, we demonstrated that supplementation with folic acid, vitamin B12 and vitamin B6 was not effective at reducing the risk of cardiovascular disease in renal transplant recipients exposed to mandatory fortification of enriched cereal grain products.
1. Whole-Grain and Refined-Grain Intakes have Opposite Relationships with Visceral Fat. Given the emerging evidence that the visceral adipose tissue (VAT) compartment is more strongly related to metabolic risk factors than subcutaneous adipose tissue (SAT), ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, MA, examined the association of whole- and refined-grain intake on these body fat depots in a large population-based cohort of ambulatory adults to gain further insight into the relation between grain intake and cardiometabolic risk. They observed that increasing intakes of whole-grain intake was associated with less VAT whereas increasing intakes of refined-grain intake was associated with more VAT; however, the association between higher whole grain intake and less VAT was not seen among those who consumed 4 or more servings per day of refined grain. This research suggests that higher intakes of whole grains may help limit the amount of harmful visceral adipose tissue, but that this beneficial effect of whole grains may be negated by consuming more 4 or more servings of refine grains per day. At this time the mechanism(s) by which whole and refined grains interact to influence VAT is unknown.
2. Higher Predicted Vitamin D Status is Associated with a 40% lower Risk of Type 2 Diabetes. The relation between vitamin D and bone health is well established, but there is accumulating evidence that vitamin D might have other functions, including involvement in the development of type 2 diabetes (T2D). To further explore the potential benefits of improved vitamin D status on risk of developing T2D, ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, MA, examined the relation between predicted vitamin D status and risk of T2D in a large population-based cohort of ambulatory adults, free of T2D. They demonstrated that individuals with the highest vitamin D status at baseline had a 40% lower incidence of T2D over 7 years of follow-up than those with the lowest predicted vitamin D status. These findings suggest that maintaining optimal vitamin D status may be a strategy to help prevent the development of T2D.