Nutrient Requirments

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

Nutrition Monitoring

Composition of Foods

Health Promoting Intervention Strategies for Targeted Populations

Health Promoting Properties of Plant and Animal Foods

Bioavailability of Nutrients and Food Components

Introduction

The ARS Human Nutrition Program held a workshop on March 7-9, 2000, in College Park, Maryland, to establish long-term national priorities.  In addition, the national program sponsored a nutrition immunology workshop on September 29, 2000, in Beltsville, Maryland, to discuss the direction for this area of research and identify any gaps in the national program. 

The Children's Nutrition Research Center at Baylor College of Medicine, Houston, Texas, hosted a forum on Dissemination of Research Information, February 9-11, 2000.  The forum was convened to share techniques currently being used, to focus on what the consumer needs and wants to know, and to devise a mechanism to help ARS and the individual Human Nutrition Research Centers promote human nutrition information more effectively. 

Cindy Davis, research nutritionist at the Grand Forks Human Nutrition Research Center, was a recipient of a Presidential Early Career Award for Scientists and Engineers, the highest honor bestowed by the U. S. government on young professionals at the outset of their independent research career.

The Nutrition Summer Institute, an annual conference with 1890's institutions to enhance research activities at those institutions and to establish a network of collaborators in community nutrition, was hosted by the Beltsville Human Nutrition Research Center (BHNRC) July 18-21, 2000, in Baltimore, Maryland.  The 'What We Eat in America' Conference was held November 2, 2000, in Beltsville, Maryland, sponsored by the BHNRC.  This conference had over 200 participants.  The newly developed computerized, triple-pass method for dietary intake was demonstrated.  ARS was a major sponsor of the 24^th Nutrient Databank Conference held July 27-29, 2000 in St. Paul, Minnesota.  The Nutrient Data Laboratory and the Food Composition Laboratory, located at the BHNRC, presented their developments, and participants identified their research priority needs.

• The Human Nutrition Research Center on Aging (HNRC) at Tufts University, Boston, Massachuttes, hosted the 29^th annual meeting of the American Aging Association, June 2-5, 2000. The theme was 'Stress in Aging: Models, Mechanisms and Interventions'.  In addition, HNRC hosted 15 student participants in the National Youth Leadership Forum on Medicine on July 20, 2000, and a Calcium Summit on January 19, 2000.  Ronald Prior and James Joseph, research scientists at the HNRC were recipients of the Alex Wetherbee Award for contributions to the blueberry industry at the North American Blueberry Council conference.  Another scientist at the HNRC, Ernst Schaefer, was the recipient of the E.V. McCollum Award of the American Society of Clinical Nutrition, for excellence in nutrition research.
  

Nutrient Requirements 

 Bone mineral density gains lost.  Researchers at the Human Nutrition Center on Aging at Tufts University conducted a study to determine whether gains in bone mineral density induced by calcium and vitamin D supplementation persisted after supplementation use was discontinued in healthy older men and women.  They found that the bone mineral density gains at the spine and hips made during three years on the supplements were lost over the two years after the supplements were discontinued.  It was recommended that for optimal benefit, elderly men and women meet their calcium and vitamin D intake requirements on a continuous basis.

Peak rates of bone calcium deposition early in adolescence . Investigators at theChildren's Human Nutrition Research Center at Baylor College of Medicine showed that increased calcium absorption and bone calcium deposition are most dramatic during early puberty and that the changes were associated with maturation of the hypothalamic-pituitary axis and physical changes of breast development.  These early changes lead to peak rates of bone calcium deposition prior to menarche in girls.  These studies led to recent revisions of the dietary guidelines for children, which now recommend increased calcium intake beginning at age 9.

Primary source of energy for developing intestine is protein .  The results of animal studies conducted atthe Children's Human Nutrition Research Center at Baylor College of Medicine showed that the overwhelming source of energy for the developing intestine of well-nourished milk-fed neonates is dietary protein.  The nutrient needs of this component of the body is very important because intestinal tissue contributes disproportionately to thebody's expenditure of energy and synthesis of protein.

Boron has a role in bone formation.  Investigators at the Grand Forks Human Nutrition Research Center have shown that dietary boron fed in nutritional amounts changed the maturation rate of developing spinal column in an animal nutrition-pregnancy model.  This finding, along with the observation that boron interacts with erythritiol, a boron-binding substance, affects fetal absorptions in the pregnancy model, suggesting that boron may be important in embryo development in humans and supports the concept that boron is an essential nutrient for humans.

No fear for manganese deficiency or toxicity.  There is concern about the possibility of either manganese toxicity or deficiency in free-living humans consuming a mixed western diet.  Due to little research conducted on this topic, researchers at the Grand Forks Human Nutrition Research Center conducted a comprehensive human study that examined health effects of consuming diets made as low or high in manganese as practically possible.  The results indicated that in the absence of exacerbating circumstances and/or dietary interactions, there is no need for young women to be concerned about manganese nutrition.

Factors contributing to weight regain in cyclic dieters. Investigators at the Western Human Nutrition Research Center found that the resting metabolism of women who are cyclic dieters was very similar to that of women who were not cyclical dieters under normal and restrictive dietary intake conditions.  However, after eating a mixed meal, cyclical dieters favored the use of carbohydrate for energy and had a decreased capability to use fat. This finding may be indicative of a metabolism that favors storage of fat and contributes to the ease of weight regain in cyclic dieters.

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

Possible mechanism for folate status influences on colorectal carcinogenesis. Dietary folate deficiency was shown by investigators at the Human Nutrition Research Center on Aging at Tufts University to produce progressive DNA strand breaks within the tumor suppressor gene p53 in rat colon.  Folate supplementation at four times the basal requirement significantly increased p53 integrity compared with the basal and deficient diets.  These data provide a plausible mechanism by which folate deficiency promotes and folate supplementation suppresses colorectal carcinogenesis.

Role of genetics in determining plasma apolipoprotein levels . The effects of genetic factors on plasma apolipoprotein levels in the Framingham Offspring Study and other populations was assessed by investigators at the Human Nutrition Research Center on Aging at Tufts University.  They found that the apoE genotype has a very significant effect on modulating plasma apoE levels.  This may be of relevance not only to coronary heart disease risk, but also to the riskof Alzheimer's disease, since carriers of the apoE-4 allele have markedly decreased apoE levels and are at increased risk forAlzheimer's disease and dementia.

Gender differences with regard to heart disease risk.  Women are at lower age-adjusted risk than men, which partly relates to their 20-25 percent higher HDL cholesterol and apoA-1 levels.  To gain an understanding of this difference, researchers at the Human Nutrition Research Center on Aging at Tufts University examined the regulation and apoA-1 secretion and production in human liver cells treated with or without estrogen.  They found that estrogen markedly increased apoA-1 gene expression.  This data helps to gain insight into understanding the indications for the use of hormonal replacement in postmenopausal women for heart disease risk reduction.

Nutrition Monitoring

Commodity Intake Database completed. This database for the Continuing Survey of Food Intake by Individuals (CSFII) 1994-96, 98 was completed by investigators at the Beltsville Human Nutrition Research Center.  It was developed for use in estimating the potential dietary exposure of humans to specific pesticides as specified in the Food Quality Protection Act of 1996.

Hunger factor in dietary record reporting. Factors influencing the accuracy of dietary record reporting are not well understood.  Investigators at the Human Nutrition Research Center on Aging at Tufts University completed a study of the effects of eating behavior patterns on the accuracy of measurements of dietary intake.  They found that reduced hunger was a significant predictor of underreporting in adults.  This finding may be used to help screen inaccurate dietary records, which will help improve dietary intake data.

Nutritional Assessment Survey (NAS) conducted in Lower Mississippi Delta. Investigators with the Lower Mississippi Delta Nutrition Intervention Research Initiative conducted this survey to describe the nutrition and health status of the population of the Lower Mississippi Delta in Arkansas, Louisiana, and Mississippi.  The survey will provide baseline data to design, implement, and evaluate culturally appropriate, sustainable nutrition intervention research in a rural region of the U.S. with the goal of reducing nutrition related chronic disease rates in three states ranked last in a recent report on health status in the U.S.  This data is currently being analyzed.

Body size and behavioral traits play role in dietary intake reporting. It has been shown that dietary assessment methods have a strong bias toward underestimation of habitual energy intake. In a study with normal weight and obese women conducted at the Western Human Nutrition Research Center, researchers found that body size and behavioral traits played a role in the ability of women to accurately self-report energy intake.  Body mass index was predictive of underreporting of energy intake by normal-weight women, and emotional factors related to depression were a determinant of underreporting in obese women.  This research is important to understanding what factors can influence the validity of dietary methods when applied to overweight and normal weight populations.

Composition of Foods

Procedure developed for measurement of folic acid in foods. A routine analytical procedure was developed for the accurate measurement of folate isomers and folic acid in foods at the Beltsville Human Nutrition Research Center.  This procedure involved extraction and chromatographic analysis for accurately quantifying the common forms of folates in foods. This will provide data for calculation of intakes of this important vitamin based on recent National Academy of Sciences recommendations and will provide accurate data to be incorporated into the U.S. National Nutrient Databank.

New method for determination of niacin. Investigators at the Beltsville Human Nutrition Research Center developed a new method for determination of niacin in infant formula, using solid phase extraction ion exchange chromatography.  The method has been recognized as an AOAC Peer-Validate Method.  This recognition allows use of this method as an alternative to the current labor intensive official AOAC microbiological method currently required to be used by private sector and regulatory food testing analysts to generate data in response to food labeling regulations.

Health Promoting Intervention Strategies For Targeted Populations

Focus group data collected from African American youth. Investigators at the University of Southern Mississippi, one of the partners in the Lower Mississippi Delta Nutrition Intervention Research Initiative, conducted focus groups with limited-income African American youth to understand socioeconomic, cultural, and environmental factors that influence this group to eat fruits and vegetables.  They are analyzing the data and looking at culturally appropriate methods for teaching African American youth about healthy eating.

Zinc status is predictive of mood disturbances and behavior problems. Hair zinc concentration in school children was negatively associated with teacher-reported anxiety and depression, withdrawal, and total adjustment problems, indicating that problems were associated with lower zinc status in a study conducted by investigators at the Grand Forks Human Nutrition Research Center, in collaboration with investigators from Texas.  Their findings provide the first evidence that zinc status is predictive of mood disturbances and behavior problems in school-aged children.  Findings indicate the need for further study to determine whether increased zinc intakes might prevent or help alleviate mood and behavior problems that directly affect school performance, cognitive and social development, and quality of life for many children.

Early nutritional deficits affect learning ability . Investigators at the ArkansasChildren's Nutrition Center found that elementary children and junior high school children who were undernourished at a younger age had slower reaction times which point to less automated work recognition, and differences in neurophysiology of specific brain areas, frontal sites, that are often linked to post-decisional information processing. These results are important because it suggests that early nutritional deficits can produce problems related to information processing that can impair learning ability.

Focus groups conducted to identify correlates of diet and physical activity among African-American girls . Focus groups were conducted by researchers atthe Children's Human Nutrition Research Center at Baylor College of Medicine on 8 year old African-American girls to identify the correlates of diet and physical activity and how best to design a summer camp and internet experience to help them and their parents change their behaviors.  Dietary fat intake, but not calories, protein, carbohydrate, or physical activity, accounted for the onset of overweight among young children.  In addition, focus group discussions revealed how parents influencechildren's fruit, juice, and vegetable intake and showed no differences by ethnic groups.

Health Promoting Properties of Plant and Animal Foods

Flavonoids as inhibitors of glucose uptake.  Investigators at the Beltsville Human Nutrition Research Center identified flavonoids as inhibitors of glucose uptake and characterized a moiety of flavonoid structure as a putative binding site for the glucose transporter.  More than ten flavonoids were investigated in U937, HL-60, and Jurkat cells to identify potent blockers for glucose transport.  Data indicated that flavonoids are potent inhibitors of glucose uptake, and flavonoids may have the potential to attenuate the surge of glucose in plasma of hyperglycemic patients.

Lutein and zeaxanthin may play a role in prevention of age-related nuclear lens opacities.  Investigators at the Human Nutrition Research Center on Aging at Tufts University examined the relationship between age-related nuclear lens opacities and usual nutrient intake from dietary questionnaires collected over a 13-15 year period from older Boston-area women.  The women had not been previously diagnosed with cataracts.  Vitamin C and lutein and zeaxanthin (carotenoids found in green leafy vegetables) intake and duration of vitamin C supplement use werefound to be inversely associated with risk of nuclear opacities.  The results support a role for vitamin C and lutein and zeaxanthin in the prevention of age-related nuclear lens opacities.

Soy protein isolate or whey protein affect breast cancer development in rats .  Investigators at the ArkansasChildren's Nutrition Center studied cellular metabolism in animals fed whey and soy diets to determine the mechanisms by which phytochemicals in soy or whey work to alter risk of chronic disease.  They found that Phase I and II enzymes that are responsible for procarcinogen activation and detoxication were elevated.  This is a protective action that could be a significant mechanism of cancer prevention by soy and whey.

Conjugated linoleic acid (CLA) not shown to have a beneficial effect.  Animal studies have found beneficial effects of CLA feeding, such as enhanced immune response, improved cardiovascular health and other health indices.  Researchers at the Western Human Nutrition Research Center conducted a study to see if similar effects could be seen in humans.  Analysis of samples and data from the study showed that CLA supplementation had no beneficial or adverse effects on a number of health parameters, including immune status, cardiovascular health, and body composition.  Further studies are needed to determine if the discrepancy between human and animal studies is due to differences in species or other factors.

Bioavailability of Nutrients and Food Components

Initial iron uptake is the major site of absorptive control.  There is a need to understand how the human body controls the absorption of heme iron, compared to nonheme because of possible, excessive body iron accumulation by men consuming western diets. Investigators at the Grand Forks Human Nutrition Research Center developed a new method to measure in humans, for the first time, the initial intestinal uptake of the two forms of iron, as well as the subsequent transfer to the body.  The results indicated that initial iron uptake is the major site of absorptive control and that this initial entry is more controlled for nonheme than for heme iron.  This information will affect the development of nutritional guidelines for the public and food industry.

Brown versus well-milled rice assessed for zinc bioavailability.  Investigators at the Grand Forks Human Nutrition Research Center assessed the nutritional impact of encouraging the use of brown versus well-milled rice by evaluating the effect of milling on the nutritional bioavailability of zinc from Philippine rice in rats.  The findings supported the use of brown rice, which would contribute more, although somewhat less bioavailable, zinc than the refined forms of rice.

Bioavailability assessed in varieties of rice.  Identifying varieties of staple plant foods that have enhanced or inferior iron bioavailability is important for plant breeding in order to identify varieties most useful for alleviating iron malnutrition.  Researchers at the U.S. Plant, Soil and Nutrition Laboratory qualitatively assessed the amount of bioavailable iron in 16 varieties of rice, using simulated digestion method and Caco-2 cells, a human intestinal cell.  This model was shown to rapidly and economically screen numerous varieties of plant foods for inherent differences in iron bioavailability.