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 grain 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 dietary intake and nutrient status 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 metabolic risk factors, inflammation, cardiovascular disease (CVD) and cancer. As part of our research on diet and metabolic risk factors, we observed that individuals with an index reflecting higher vitamin D status had less increase in fasting glucose concentrations as they aged. As part of our research on the relation between diet and inflammation, we demonstrated that individuals with greater levels of inflammation, based on higher levels of multiple blood biomarkers that reflect inflammation in a variety of tissues, were more than three times more likely to have inadequate blood levels of vitamin B6. As part of our research on diet and CVD, we showed that greater intake of the carotenoid lycopene, which is derived largely from consumption of tomato products, was associated with a 15 to 25% lower risk of CVD. As part of our research on the role of diet on cancer risk, we observed that the risk of esophageal squamous cell carcinoma, the sixth most common cancer in the world, was 60% lower among Iranian men and women who consumed a Mediterranean-style diet. 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 conducted 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 the whole wheat feeding trial, we also conducted a pilot study to see if whole wheat consumption, which is rich in fibers that are believed to enhance the growth of beneficial gut bacteria, modified the types and proportions of gut bacteria (Objective 1). There is growing evidence that the types of gut bacteria may influence aspects of health from inflammatory bowel disease to weight gain. As part of our research on B vitamins and cognitive function (Objective 5), we have terminated enrollment and 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. We have begun to explore the potential effects of B vitamin supplements on age-related cognitive changes using the data available to us from testing prior to the termination of the study. Our accomplishments related to this objective will help us understand the role of nutrition in preventing age-related cognitive decline.
1. Lycopene and tomato product intake reduce incidence of cardiovascular disease (CVD). The limited number of prior studies examining the relationship between CVD and lycopene intake, a carotenoid derived mainly from tomatoes, failed to show any benefits of lycopene intake in spite of experimental evidence suggesting the opposite. ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, Massachusetts used repeated measurements of diet for up to ten years to characterize usual long-term intake of lycopene and tomato products in order to fill the gap in availability of longitudinal data. We observed that incidence of CVD was 15-25% lower among those with the highest lycopene intakes compared to those with the lowest intakes; similar results were seen based on the intake of tomato products. Including more tomato products as part of a healthy diet pattern may provide added benefit against the development of CVD, which remains a major public health concern for Americans.
2. Better vitamin D status slows the age-related increase in fasting blood glucose (sugar) levels. There is a growing belief that poor vitamin D status is associated with a higher risk of type 2 diabetes, but there is little evidence to suggest that vitamin D effects pre-diabetic metabolic conditions related to the development of diabetes, such as impaired fasting glucose. To help address this gap in our knowledge, ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, Massachusetts examined the relation between vitamin D status using previously validated vitamin D score and increases in fasting plasma glucose concentrations among adults without type 2 diabetes. We observed that blood glucose levels among individuals with lower vitamin D scores, indicative of poor vitamin D status, were 50% greater than levels for those individuals who had high vitamin D scores after 7 years of follow-up. These findings suggest that a better vitamin D status might be one means to slow the age-related increase in fasting glucose levels resulting in lower risk of impaired fasting glucose, consequently helping to prevent the later development of type 2 diabetes.