1a. Objectives (from AD-416):
1. Determine the ability of bioactive plant-based foods, including carotenoid-rich foods to exert biological functions and affect genomic stability. 2. Determine the vitamin A requirement of healthy U.S. adults.
1b. Approach (from AD-416):
By recruiting older adults (>60 yr, men and post-menopausal women) without and with metabolic syndrome to ingest bioactive plant foods or histidine dipeptide rich foods, we will measure plasma total antioxidant performance, plasma in vivo oxidative stress biomarkers, plasma water-soluble and fat-soluble antioxidants (carotenoids, tocopherol, ascorbic acid, and uric acid), plasma biomedical parameters to determine the ability of bioactive plant-based foods, including carotenoid-rich foods, to exert biological functions and affect genomic stability. Also, to explore a possible correlation between a change in serum apoE and a change in Macular Pigment (MP) density, we will measure HDL subpopulations by nondenaturing 2d gel electrophoresis, immuno-blotting, and image analysis. We will measure lipoproteins, antioxidative capacity, and markers of inflammation in order to better define the mechanism by which decreased body weight is associated with increased MP in humans. Using the stable isotope labeled vitamin A (labeled in three different levels, ^13 C_4 , ^13 C_8 , ^13 C_12 – retinyl acetate) and apheresesautologues technique on human volunteers, we will measure the enrichment of these labeled retinols in human circulations and mathematical modeling to determine vitamin A bioavailability and the requirement of vitamin A through an intervention trial with various levels of vitamin A.
3. Progress Report:
ARS-funded researchers from Tufts University in Boston, MA continue to work on efficacy studies to determine vitamin A values of biofortified provitamin A carotenoids in staple crops. These crops studied include the effects of Golden Rice on adults in China and the US and the effects of high beta-carotene yellow maize on Zimbabwean adults. Research in the lab supports the notion that staple crops fortified with beta-carotene are promising plant foods to combat vitamin A deficiency. Another study found that components in chicken breast counteract metabolic risk factors therefore providing essential information for a dietary strategy in preventing the progression of metabolic syndrome. ARS funded scientists at Tufts University in Boston, MA have also continued their research efforts in the area of nutrition and age-related eye health with the publication of three papers relating to the role of the carotenoid lutein in age-related macular degeneration. They have also published work on dietary content of the xanthophyll carotenoids in common foods that are not contained in the U.S.D.A. carotenoid database. Furthermore, researchers are extending their work in age-related neural (eye) health with the examination of the role of lutein in age-related cognition. The first step in these efforts was establishing that macular pigment (lutein embedded in the macula of the retina) can be used as a biomarker of brain lutein. These findings will be used in recently funded research that evaluates the effect of an intervention with food sources of highly bioavailable lutein on cognitive function in older adults with mild cognitive impairment. Macular pigment density, which is measured non-invasively, will be measured and changes will be evaluated relative to changes in cognitive function with the premise that increases in macular pigment reflect increases in brain levels of lutein. This is of interest given the results obtained from collaborations with the Health ABC Study and the Georgia Centenarian Study in which cross-sectional analysis was performed on older adults. In the Health ABC study, higher macular pigment density was related to better cognitive performance. In the Georgia Centenarian Study, brain tissues from 49 decedents were analyzed for carotenoids. Among the dietary carotenoids, lutein showed the strongest relationships with pre-mortem measures of cognition. Other efforts include successful completion of a clinical trial that evaluated the bioavailability of nutrients that are suggested to be needed for optimal eye function (vitamin C, E, beta-carotene, zinc, and copper) contained in softgels or tablets. Other ongoing research involves meta-analyses evaluating the role of selected nutrients in age-related macular degeneration.
1. Relationship established between retinal and brain lutein. ARS-funded scientists at the JMUSDA-HNRCA at Tufts University in Boston, Massachusetts found that lutein levels in the macula of the retina reflect lutein levels in the primate brain. Macular pigment (lutein in the macula) can be measured non-invasively in humans. Thus, macular pigment density is a biomarker of brain lutein. Our work showed that in brain lutein levels are significantly related to pre-mortem measures of cognition and that macular pigment is a biomarker of brain lutein. Macular pigment assessment may be an important tool to confirm the effect of a dietary intervention containing lutein on cognitive function in the elderly. Nutritional Interventions are cost effective, rational approaches to combat age-related cognitive decline. This is important because age-related cognitive decline is expected to rise due to the increase in the aging population.
2. Biofortified rice and maize are good sources of vitamin A to combat global vitamin A deficiency. Through evaluation of biofortified plant foods, especially staple crops biofortified with provitamin A beta-carotene, ARS-funded researchers at JMUSDA-HNRCA at Tufts University, Boston, Massachusetts, found that the staple plant foods beta-carotene fortified Golden Rice and yellow maize, are good sources in providing vitamin A. In consideration of world-wide vitamin A deficiency, biofortification of staple crops that are enriched with beta-carotene might be a long term and sustainable solution to combat vitamin A deficiency globally.