• Introduction
• Nutrient Requirements
• Diet, Genetics, Lifestyle, and the Prevention of Obesity and Disease
• Nutrition Monitoring
• Health Promoting Properties of Plant and Animal Foods
• Bioavailability of Nutrients and Food Components

 Introduction 

Within the past year several activities occurred at the Agricultural Research Service (ARS) Human Nutrition Research Centers and locations.  Some of these activities are highlighted below. 

In May, the Human Nutrition Research Center on Aging (HNRCA) at Tufts University, Boston, Massachusetts, held an event to recognize human studies volunteers and community agencies that have assisted with recruitment efforts as the kick off for the 20^th anniversary for the Center.  The event was held with cooperation and participation of the regional office of the Administration on Aging in celebration of Older American’s Month with the theme “The Many Faces of Aging.”  Human studies volunteers and representatives of community agencies were recognized for their efforts in support of the research completed over the past 20 years.  The Center has formed a Speaker’s Bureau which lists nutrition topics and languages available for presentations in the community by scientists from the Center.  The response to the Speaker’s Bureau has been very positive as this is an opportunity to provide nutrition information back to the local communities that are supportive of recruitment efforts. 

The Community Nutrition Research Group of the Beltsville Human Nutrition Research Center (BHNRC), Beltsville, Maryland, held the 2001 Food and Nutrition Summer Institute in Accra, Ghana, which was attended by students and faculty from eight U.S. universities and three African countries. 

Dr. Wayne C. (Chris) Hawkes from the ARS Western Human Nutrition Research Center (WHNRC), Davis, California, received the 2001 Klaus Schwartz Commemorative Medal from the International Association of Bioinorganic Scientists for outstanding achievement in biological trace element research for the discovery of selenocysteine transfer RNA and its role in selenoprotein biosynthesis.  In addition, Dr. Robert Jacob, WHNRC, received a Distinguished Service Citation from the Illinois College Alumni Association.  

Scientists from the ARS Lower Mississippi Delta Nutrition Intervention Research Initiative (LMDNIRI), Little Rock, Arkansas, held information sharing meetings (June September) with community leaders in 9 counties in the lower Mississippi Delta of Arkansas, Louisiana, and Mississippi to advance communication with community stakeholders. 

Significant Accomplishments by Components 

Nutrient Requirements 

Nutrient shown to correct a fundamental agerelated change in an immune cell.  Dysregulation of the immune response is the most significant and reproducible agerelated change reported across all species.  Researchers at the HNRCA showed that T lymphocytes from old mice exposed to vitamin E showed significant increase in the ability of nave cells to progress through multiple cell cycles.  T lymphocytes exhibit the most dramatic agerelated changes.  This is the first time that a nutrient has been shown to correct a fundamental agerelated change in T cells.  This finding may have significant implications for improving the overall health status of the aged by improving immune function. 

Memory function associated with folate status.  Researchers at HNRCA showed that lower memory function was associated with lower folate levels and higher homocysteine levels.  Depression was also found to be more common in those with low folate and high homocysteine blood levels.  These findings provide further evidence that inadequate folic acid status and vitamin B12 nutrition are related to cognitive decline and depression in elders. 

Novel zinc transporters identified.  Researchers at the WHNRC have identified and characterized two novel zinc transporters that are important for zinc across intracellular membranes in mammalian cells.  These may be the primary targets for dietary zinc regulation.  Zinc is an essential element that plays important roles in DNA synthesis, antioxidant defense, and gene expression regulation.  The risk of inadequate zinc intakes is a common public health problem affecting nearly half of the world’s population.   

Findings help explain why low magnesium status is associated with many health disorders. Human volunteers at the Grand Forks Human Nutrition Research Center (GFHNRC), Grand Forks, North Dakota, were fed diets containing inadequate, marginal, and adequate amounts of magnesium over a 6 month period to ascertain whether a systemic neurogenic inflammatory response is of primary importance during magnesium deprivation.  Magnesium deprivation resulted in elevated circulating substance P; changes in the release of other neurogenic peptides, including decreases in calcitonin generelated peptide and neuropeptide Y; and an apparent increase in oxidative stress as indicated by reduced circulating glutathione and increased extracellular superoxide dismutase.  These findings may be the reason that numerous epidemiological findings and magnesium supplementation trials show that a low magnesium status is associated with numerous disorders including coronary heart disease, hypertension, migraine headaches, sleep disorders, mood disturbances, and osteoporosis. 

Chromium supplementation not necessarily beneficial.  Researchers at the GFHNRC found supplements containing picolinic acid may have negative consequences for menstrual symptomatology and the chromium supplementation in physiologic amounts does not benefit menstrual symptomatology, cognitive function, or psychomotor performance.  Expected increases in plasma and urinary chromium with the chromium picolinate supplement, compared to placebo, were found in the women assessed.  The supplements increased reported severity of intermenstrual anxiety, depression and negative mood, and premenstrual pain, water retention, and negative mood. 

Concentration of individual fatty acids in the diet may affect fat cell growth.  Individual fatty acids, many of which are obtained from the diet, may stimulate or inhibit the expression of specific genes and consequently modulate the differentiation and growth of fat cells, including the development of excess fat (obesity).  Researchers at the Children’s Human Nutrition Research Center (CHNRC) at Baylor College of Medicine, Houston, Texas, differentiated pig or human precursor cells to fat cells in the presence and absence of individual fatty acids to determine whether they stimulated, inhibited, or had no effect on differentiation.  Many individual fatty acids increased differentiation and gene expression, in a concentrationdependent manner, after shortterm incubation, whereas some fatty acids had no effect.  Potentially, an increase or decrease in the concentration of individual fatty acids in the diet may be a mechanism to control the growth of fat cells. 

Substantial portion of American children have inadequate calcium intakes.  Researchers at CHNRC wanted to determine the effects of low calcium intakes on children, so they conducted a study in which healthy children were given diets with low and high calcium intake and they measured how much calcium they absorbed and retained in their bodies.  Preliminary data showed that, when calcium intake in girls was very low, they adapted by increasing calcium absorption; however, this adaptation was inadequate to meet the deficiency associated with the low intake.  This demonstrates that a substantial proportion of American children are not receiving a healthy amount of calcium in their diet, and that the recent dietary intake recommendations for calcium are crucial to meeting bone calcium requirements. 

Diet, Genetics, Lifestyle, and the Prevention of Obesity and Disease 

Selenium deficiency increases the virulence of human influenza A virus.  Researchers at BHNRC, in collaboration with researchers at the University of North Carolina, showed that virulence of a mild strain of human influenza A virus is increased in mice deficient in selenium.  This increased virulence was accompanied by 29 changes in the gene for the virus matrix protein, a region of the viral genome that is usually thought to be quite stable.  These findings could have significant implications for practical public health as well as for theoretical ideas concerning the effects of nutrition on viral gene structure and function. 

Gene mutation may not make a difference in iron absorption.  The discovery of the specific genetic mutation associated with the iron storage disorder hemochromatosis, and the relatively high frequency of heterozygous carriers among those of Northern European ancestry, has raised concerns about increased iron absorption and the risk for chronic disease in people with this genotype.  Researchers at GFHNRC in a preliminary study observed that subjects identified as heterozygous for the Hfe C282Y mutation showed no difference in either heme or nonheme iron absorption, compared with absorption by those with no mutation.  More studies on subjects with this genotype are ongoing.  If these findings are confirmed it could mean that people heterozygous for hemochromatosis do not have excessive iron absorption, which will be useful information to policy makers in regard to food fortification.

Selenium status affects DNA methyltransferase activity.  Several observations implicate a role for altered DNA methylation in cancer pathogenesis.  Researchers at GFHNRC conducted studies to determine whether a DNA methyltransferase inhibitor would alter the effect of dietary selenium on the formation of aberrant crypts, a preneoplastic lesion for colon cancer.  The results of the study suggested that decreased DNA methyltransferase activity may protect selenium deficient animals against colon cancer susceptibility.  

Zinc might affect abundance of the coppertransporters.  Researchers at the GFHNRC used an in vitro cell culture model to show by Western blotting techniques that at least one of the copper transport proteins, called Wilson’s disease protein, was not affected by zinc.  However, in the rat model, the mRNA for the Menke’s transporter was reduced by onehalf in the gut cells when the animals were fed high zinc diets.  This work shows that zinc might affect the abundance of the copper transporters, which would suggest a mechanism for the initiation of low transporters, which suggests a mechanism for the initiation of low copper status in humans and animals that consume excess zinc in their diets. 

Improved understanding of milk synthesis and yield.  Researchers at the CHNRC devised a method to modify large transgenes in order to functionally analyze potential regulatory elements in the casein gene cluster.  Since milk from mice that carry a targeted mutation in the USF2 gene has reduced lactose and protein content, this should provide insight into the role that conserved regions play in the casein gene regulation.  These data may improve our understanding of milk synthesis.  In another study, cell proliferation and death were compared in mammary glands from wild type and mutant mice during early lactation.  Reduced proliferation was found in the mammary glands of mutant mice.  This result supports the suggestion that factors, such as USF2, which maintains mammary cell proliferation during the early postpartum period, are important to maximizing milk yield, and potentially may impact on human lactation performance. 

Nutrition Monitoring 

Supplemental Children’s Survey results released.  A CDROM prepared by investigators at the BHNRC was released of the dietary and all related sociodemographic data of the respondents as well as survey instruments, documentation, and technical support data files.  Dietary data were collected from 5,600 children from birth through 9 years of age in response to the Food Quality Protection Act of 1996.  The release of the CDROM and data tables give researchers and educators access to survey results and methodology for use in various programs and for public policy decisions.  The database was developed in collaboration and support from Environmental Protection Agency and will be used for risk assessment from dietary exposure to pesticide residues, and for other data users who can make use of food consumption data expressed in terms of agricultural commodities. 

No significant problems foreseen for USDA Automated MultiplePass Method’s use in NHANES Mobile Examination Center.  A pilot test was conducted by researchers at the BHNRC to assure that the USDA Automated MultiplePass Method and related systems integrated into the National Health and Nutrition Examination Survey (NHANES) Mobile Examination Center “environment” operated successfully so that national data collection using the new USDA instrument will go as scheduled in January 2002.  The collection was designed to mimic the NHANES “environment” as much as possible.  Two days of dietary intakes were collected with day 1 being collected in person and day 2 collected by telephone.  This is comparable to the protocol that will be used in NHANES in 2002.  While recommending a few suggestions for ease of operation, the interviewers reported no significant problems with the instrument or related operating systems that they used.  The pilot study was successful, with the USDA MultiplePass Method and related systems performing without any problems. 

Composition of Foods 

Method developed for determining heme and nonheme iron.  The differentiation between heme iron (iron found in hemoglobin and myoglobin) and nonheme iron (iron found in other organically complex forms and in inorganic forms) is crucial to determining optimum diets for increasing or decreasing iron absorption.  Researchers at the BHNRC developed a method for determining the two forms of iron using size exclusion chromatography and sequential spectrophotometric and atomic spectrometric detectors.  This methodology will ultimately be used, in collaboration with the ARS Nutrient Data Laboratory, to characterize the heme and nonheme iron content of U.S. meats. 

Nutrient Database for Standard Reference (SR) released.  Researchers at the BHNRC developed the Nutrient Database for SR, Release 14 (SR 14), which was released in July 2001.  SR 14 is available to the public and can be accessed at www.nal.usda.gov/fnic/foodcomp and on CDROM.  SR 14 provides estimates of composition for up to 80 components and approximately 6,200 foods. 

New sources of vitamin K identified.  Researchers at the HNRCA, in collaboration with researchers at the BHNRC, analyzed approximately 500 representative foods from different food groups for two forms of vitamin K as part of the National Food and Nutrient Analysis Program.  This is the first time that numerous foods, including certain mixed dishes, snack foods, berries, and sauces have been identified as potentially important dietary sources of vitamin K.  These data will be incorporated into the USDA Nutrient Databank System, the most widely used nutrient database. 

Health Promoting Intervention Strategies For Targeted Populations 

Interactive multimedia nutrition education program developed that increased fruit & vegetable consumption in children.  The Squire’s Quest!, a psychoeducational interactive multimedia nutrition education game, was designed to help 4^th grade children increase their consumption of fruit, 100 percent juice, and vegetables (FJV) for chronic disease prevention by researchers at the CHNRC.  Children randomly assigned to participating in the 5week program increased their consumption of FJV by 1.3 servings per day in comparison to those not participating in the program.  Thus, psychoeducational interactive multimedia nutrition education game technology holds promise for enabling children to eat more FJV and reduce chronic disease risk. 

Focus group sessions conducted to examine factors associated with healthy food choices.  To determine lower Mississippi Delta resident’s perceptions of problems associated with the acquisition and consumption of healthy foods, food security, grocery shopping, and factors that influence behavior changes in the consumption of healthy foods, scientists with the LMDNIRI conducted 36 focus group sessions involving a total of 347 participants in 9 counties/parishes in the lower Mississippi Delta of Arkansas, Louisiana, and Mississippi.  This information serves to guide decisions on the types of nutrition interventions that are acceptable and sustainable to the Delta residents. 

Health Promoting Properties of Plant and Animal Foods 

Compounds found in blueberries and cranberries have health benefits.  Researchers at the HNRCA showed that polyphenolics isolated from blueberries and cranberries protected endothelial cells against stressor induced oxidation and inflammation.  These compounds may have beneficial actions against the development of vascular diseases and may contribute to the reduction of agerelated deficits in neurological impairment. 

Plant sterol enriched margarines shown to reduce cholesterol levels.  The response to blood lipid levels to consumption of reducedfat spreads enriched with soybean oilderived plant sterols was examined in subjects following a National Cholesterol Education Program Step 1 diet by researchers at the HNRCA.  Subjects with elevated low density lipoprotein (LDL) cholesterol levels lowered their LDL cholesterol levels approximately 78 percent above that of a baseline diet by adding two servings of plant sterol enriched margarine per day.  It has been estimated that for every 1 percent reduction in LDL cholesterol, one obtains a 12 percent reduction in coronary heart disease risk. 

Farming methods identified which yield higher concentrations of selenium.  Selenium is an essential nutrient that has been shown to have health benefits.  Researchers at the GFHNRC, in collaboration with university partners, have identified farming methods that result in the production of highselenium wheat, broccoli, and beef.  They have determined geographical and geochemical factors that affect accumulation of selenium in these foods, and have determined the relative effectiveness of these foods for preventing colon cancer.  Many persons would like to consume more selenium through their diet, but different foods contain different forms of selenium, and the optimal food form(s) of selenium have not been identified.  Investigation as to identification of the various forms of selenium and their effectiveness in cancer prevention is ongoing. 

Bioavailability of Nutrients and Food Components 

Formation of chylomicrons required for vitamin A and carotenoid absorption.  Researchers at the BHNRC, in collaboration with those at the State University of New York, developed a model system using human intestinal cells (CaCo2) in culture that accurately mimics the intestinal absorption of fatsoluble nutrients like vitamin A and carotenoids.  This system was used to demonstrate that the formation of intestinal lipoproteins called chylomicrons is absolutely required for vitamin A and carotenoid absorption, and that the markedly reduced bioavailability of cisisomers of carotenoids is due to discrimination of these isomers and the level of uptake by the intestinal cell membrane.  This model system allows for the study of molecular regulation of vitamin A and carotenoid absorption from the gut. 

Higher zinc concentrations found in select wheat varieties.  Zinc deficiency is thought to be wide spread in various countries resulting in increased mortality and morbidity rates especially among resourcepoor families.  Wheat grain is a major staple plant food that contains relatively low bioavailable levels of zinc, and this is thought to contribute to zinc deficiency in many countries.  Researchers at the U.S. Plant, Soil and Nutrition Research Laboratory, Ithaca, New York, in collaboration with investigators at the Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), tested the bioavailability of zinc in the grain of 14 select zincdense genotypes of wheat using a rat model.  The results showed that it is feasible to select for higher zinc concentrations in wheat grain using traditional plant breeding methods that will provide significantly more bioavailable zinc compared to currently available commercial varieties.  Consumption of zincdense varieties of wheat will contribute greatly to the reduction zinc deficiency globally. 

Women differ from men in their ability to adapt to low iron diets.  Premenopausal women absorbed 45 times more iron from a high bioavailability diet, compared with a low bioavailability diet, and, in contrast with men, their adaptation to dietary iron bioavailability was minimal according to researchers at the GFHNRC.  Concerns about iron deficiency or excess may be moderated if people are able to adapt their iron absorption to differences in dietary iron bioavailability.  These findings demonstrate the benefit of diets containing lean meat and foods rich in vitamin C (known to enhance iron absorption), without excessive amounts of phytic acid (which can bind iron) from legumes, whole grains, and tea, in allowing menstruating women to meet their high iron requirements.                                                                                                                       

Labeling technique developed to study vitamin K bioavailability.  Researchers at the CHNRC, in collaboration with those at the HNRCA, perfected a growth procedure for labeling plants with deuterium, a stable isotope of hydrogen.  This procedure allowed them to label vitamin K molecules within the plants, and to subsequently track this molecule in plasma samples following vegetable ingestion by human subjects.  The labeling technique and analytical methodologies will enable them to determine vitamin K bioavailability from different foods, and thereby improve recommendations for the dietary intake of this essential nutrient.