2009 Annual Report
1a.Objectives (from AD-416)
The general objective is to determine how current and proposed changes to the American diet that may adversely affect intake and/or how bioavailability of the essential mineral nutrients can be modified to enhance trace element nutrition, with emphasis on selenium (Se), iron (Fe), zinc (Zn), and copper (Cu). Specific objectives are:
Objective 1: Determine how shifts in agricultural and dietary practices, such as the availability of functional/genetically modified foods and emphasis on plant-based diets with reductions in meat consumption will impact the intake, bioavailability, and dietary requirements of minerals. This objective will address the production of foods with enhanced bioactive Se compounds, and assess their ability to enhance health, especially by controlling oxidative stress and reducing cancer risk. The impact of organic farming methods will also be assessed (Finley). It will also address the practical impact of dietary changes that emphasize plant-based diets on meeting nutritional needs for Fe and Zn (Hunt).
Objective 2: Determine the effectiveness of current and proposed mineral fortification/supplementation practices for improving mineral nutrition while avoiding excessive or imbalanced mineral intakes. This objective will evaluate the bioavailability of Fe fortificants such as elemental Fe and micronized, encapsulated Fe compounds in human studies (Hunt).
Objective 3: Determine the mechanisms of uptake, transport, and retention of food minerals and how mineral nutritional status influences these mechanisms to impact the bioavailability of essential minerals, non-nutritive metals, and other food components. Cell and whole animal models will be employed to elucidate how the modifications of mineral content of foods can influence the biochemical regulation of specific transporters, cellular trafficking, and interactions of minerals such as Zn, Fe, Cu, Cd, Se, and Mn. (Reeves).
Problem to be addressed with increased funds: Elucidate the roles and diets in support of optimal health and prevention of obesity and related illnesses, cardiovascular disease, osteoporosis and cancer.
Problem to be addressed with increased funds (FY05): Under Performance Measure 4.1.1 of the ARS Strategic Plan and the NP107 Action Plan, this project will develop an enhancement to the food supply by increasing the nutritional value of beef.
Objective modification FY05: Increase the amount of omega-3 fatty acids in beef to a nutritionally significant level by feeding flax. Demonstrate that the increase in omega-3 fatty acids in the meat are sufficient to have a physiological effect. Study feasibility of increasing selenium in beef to levels that will have an impact on human health when the meat is consumed at recommended levels. This may include studies of organic form of selenium in beef, stability with varying cooking methods, sensory issues, bioavailability and health effects in both steers and consumers.
1b.Approach (from AD-416)
Methodology will include tests of agricultural conditions affecting the amounts and forms of minerals incorporated into in foods; in vitro, cellular, and animal models of mineral transport and absorption; and human experiments with controlled diets to assess mineral absorption, retention, and biological function and to model nutritional requirements.
Specific objectives to be accomplished with increased funding: To study the roles of foods, particularly those produced in the Northern Plains, in the support of health. This work is to be multi-disciplinary, including collaborations such as with the University of North Dakota School of Medicine and Health Sciences and North Dakota State University.
We conducted many studies to assess mineral utilization and bioavailability with changing diets and agricultural practices. A major accomplishment from the final year of this project is listed below. Other most significant accomplishments over the life of this project included –.
1)Developed a mathematical algorithm to estimate dietary zinc absorption from food composition data, a useful tool to evaluate the diets of populations at risk of zinc deficiency;.
2)Impaired iron absorption in copper deficient animals was associated with a reduction in copper containing hephaestin protein, copper deficiency impaired red blood cell formation, and excess dietary iron did not cure the anemia of copper deficiency. An understanding of the role of copper in iron metabolism and blood cell formation help set dietary copper recommendations;.
3)Excess cadmium retention in animals marginally deficient in zinc, iron and calcium is independent of metallothionein protein, suggesting that metallothionein was not required to cadmium retention when it was fed to animals marginally deficient in zinc, iron and calcium;.
4)Delineated mechanisms of antioxidant activity of sulforaphane and selenium from plant foods. An improved understanding of how diets influence oxidative stress helps determine dietary recommendations that can reduce the risk of chronic diseases;.
5)Dry bean consumption improved blood cholesterol. These results are useful for setting dietary guidelines;.
6)Serum pro-hepcidin, a peptide hormone, was not correlated with iron absorption in women, suggesting limitations of the commonly used assay of pro-hepcidin and the need of a more specific assay;.
7)Selenium from high-selenium wheat was highly bioavailable, but it varied in different mill fractions of wheat; .
8)Phytic acid inhibition of zinc absorption was not affected by dietary calcium fortification, suggesting that calcium in the range normally consumed did not interfere with zinc absorption, even at highly fortified levels;.
9)Hemoglobin as the sole source of dietary iron did not support adequate iron status in rats, indicating that rat was not a good model for humans to study the utilization of iron from hemoglobin; 10) High bioavailability diets enabled humans to adaptively increase zinc absorption in response to low zinc intakes. These results are useful for setting dietary zinc recommendations and for improving human diets to reduce zinc deficiency; 11) Dietary guidelines emphasizing whole grains and other sources of phytic acid reduced iron absorption. It suggests a greater risk of dietary iron deficiency with the food recommendations and emphasizes the need to further modify and balance nutrients and food guideline to meet multiple nutritional goals. This research project will not be continued because of the Center’s re-direction to obesity-related research. However, some results from this research project (e.g. high-selenium crops produced in Northern Plains) will be useful for a new research project, "Dietary Modulation of Obesity-Related Cancer by Selenium".
Selenium from high-Se soybeans is highly bioavailable. Soy is a plant source of dietary protein and selenium is an essential mineral nutrient to humans. Northern Plains are rich in selenium in its soil, and soybeans produced in Northern Plains are high in this nutrient. We assessed bioavailability of selenium from the protein isolate and tofu (bean curd) prepared from a high-protein soybean cultivar developed for Nebraska producers and from a commercial line of soybeans produced in South Dakota. Selenium from these products was highly bioavailable to selenium-deficient animals compared with selenomethionine, a food form of selenium. These results will lead to further studies investigating the nutritional values and health benefits of high-selenium soybeans, and these results will also increase the marketability of soybeans produced in Northern Plains, particularly to selenium-deficient countries.
Combs, G.F., Nielsen, F.H. 2009. Health Significance of Calcium and Magnesium: Examples from Human Studies. In: Cotruvo J., Bartram J., editors. Calcium and Magnesium in Drinking-water: Public health significance. World Health Organization Press. p. 85-95.
Hunt, J.R., Johnson, L.K., Roughead, Z.K. 2009. Dietary Protein and Calcium Interact to Influence Calcium Retention: A Controlled Feeding Study. American Journal of Clinical Nutrition. 89:1357-1365.
Hunt, J.R., Beiseigel, J.M. 2009. Dietary Calcium Does Not Exacerbate Phytate Inhibition of Zinc Absorption By Women From Conventional Diets. American Journal of Clinical Nutrition. 89(3): 839-843.
Hunt, J.R., Zito, C.A., Johnson, L.K. 2009. Body Iron Excretion by Healthy Men and Women. American Journal of Clinical Nutrition. 89(6):1792-1798.
Murphy, K.M., Reeves, P.G., Jones, S.S. 2008. Relationship between yield and mineral nutrient concentrations is historical and modern spring wheat cultivars. Euphytica. 163:381-390.