2013 Annual Report
1a.Objectives (from AD-416):
Objective 1: Determine the absorption of dietary calcium, magnesium, iron and zinc in children and the influence of other nutrients and dietary factors on the absorption.
Sub-objective 1.A: Evaluate the effects of supplemental vitamin D in enhancing calcium absorption in healthy children 4 to 8 yrs of age.
Sub-objective 1.B: Assess the absorption of magnesium and zinc in healthy children 4 to 8 yrs of age.
Sub-objective 1.C: Determine the effects of a diet lacking in meat (lacto-ovo vegetarian diet) on iron status in small children using a highly precise stable isotope method to measure iron status as determined by absorption of iron (reference dose).
Objective 2: n/a
Objective 3: Characterize dynamic indices of bone formation by quantitative histomorphometry and micro computed tomography in 7 mouse models developed in our laboratory.
Objective 4: Quantitate specific gene expression by qRT-PCR in calvarial osteoblasts derived from appropriate models to clarify the specific roles of each knockout gene.
Objective 5: Determine the effects of castration, iron loading, ASC feeding and plant derived antioxidants on bone parameters in vivo.
1b.Approach (from AD-416):
The goal of our research is to provide data to enhance the development of nutritional guidelines, especially as related to mineral nutrition, in children. Using both human experimentation and cell culture models, we are studying methods of delivering the key minerals of calcium, zinc, and iron in the diet so as to optimize health outcomes. This is done by evaluating enhancers of mineral absorption, such as ascorbic acid, prebiotic fibers, and vitamin D and by considering nutrient:nutrient interactions that may limit mineral absorption such as an excess in the zinc:copper intake ratio. We will conduct a controlled trial of vitamin D supplementation to assess the effects of vitamin D status on calcium absorption in small children. We will evaluate different types of whole diets (lacto-ovo vegetarian) on iron status and the effects of differing intakes of zinc on zinc and copper absorption. We will determine if benefits previously seen for prebiotic fibers in enhancing calcium absorption also occur for iron absorption. These studies will utilize stable isotope techniques so as to provide accurate, practically applicable information that may be obtained from the study populations in a safe manner. In vitro studies will seek to identify genetic basis for mineral absorption and to develop appropriate models for evaluation of mineral absorption. Taken together, this project will provide novel information directly useful to government, industry, and the consumer related to dietary requirements. These data will have global application and provide a strong basis for evidence-based nutritional recommendations to be developed. Additional studies will explore the roles of aldose reductase and aldehyde reductase in modulating oxidative stress in cells, as well as their separate role in providing the starting substrates for the ascorbate synthesis pathway in mice. As a result we will have a better understanding of the role and importance of vitamin C in our diet.
During this year we completed final analysis and published our research on the effects of vitamin D supplementation in 4- to 8-year-old children. We further completed our research and published our data about the role of magnesium in bone health in children. Related to the calcium and vitamin D aspect of the study, we found that calcium absorption was not affected by providing either a placebo or a 1000 IU/day supplement to the children for about 2 months. This means that the current Recommended Dietary Allowance (RDA) likely meets the physiological requirements of children in this age group. Related to magnesium, Children's Nutrition Research Center researchers found a significant relationship between magnesium intake and dietary absorption of that magnesium and bone mineral content in 4- to 8-year-old children. This relationship was closer than that for calcium intake. It is likely that the role of magnesium is positively affecting hormones controlling bone health rather than a direct effect at the bone surface. Regardless, these data suggest that further dietary emphasis on magnesium intake may be of value. Magnesium is found in dairy but also in certain vegetables and nuts. During this year we completed our study of iron absorption in vegetarian children. These studies have been analyzed, and we are currently interpreting the results. Our preliminary findings show a relatively low level of iron absorption and a significant effect of calcium on decreasing iron absorption. That is, children with the highest calcium intake had the lowest iron absorption. We are currently looking at dietary patterns in this population and preparing these data for both abstract submission and future publication.
Magnesium in bone health. An important, but poorly investigated mineral for bone health in children is magnesium. Researchers at the Children's Nutrition Research Center in Houston, Texas, determined that there was a significant relationship between the amount of magnesium in the diet and the amount of mineral in bone. This relationship was such that increasing the amount of magnesium in the diet led to substantially more dense and thus likely stronger bones. These findings may be important in developing dietary recommendations for children that include emphasis on key sources of magnesium such as dairy products, vegetables, and nuts.