A national program workshop is scheduled for March 7-9, 2000. The purpose of the workshop is to establish long-term national priorities for the ARS Human Nutrition Program.

Selected Accomplishments for Fiscal Year 1999 (listed by Component)

Data collection completed for the Supplemental Children's Survey. This was supplemental data to the CSFII 1994-96 Survey. Dietary data were collected from over 5,200 children from birth through 9 years of age in response to the Food Quality Protection Act of 1996.

New data released on the Food Surveys Research Group Web site. Over 300 tables summarizing data by region, income, Food Stamp participation, race, Hispanic origin, and Pyramid servings from the three-year combined 1994-96 CSFII/Diet and Health Knowledge Survey (DHKS) were released on the Web site (www.barc.usda.gov/bhnrc/foodsurvey/home.htm). The data in the tables were collected from over 16,000 individuals nationwide and are the most current available on the diets of Americans.

Mean energy expenditure (EE) may be overestimated by 7-day recalls. The factors used for physical activities are normally determined by measuring how much energy is expended while a person is performing that activity. To assess the accuracy of dietary intake records and activity questionnaires, energy requirement estimates are compared to free-living energy expenditure measurements using doubly labeled water. To compare EE determined by doubly labeled water and EE from validated physical activity instruments (7-day diaries and 7-day recalls), 24 men who were consuming a controlled diet were studied. Mean EE was overestimated by the 7-day recalls, which can be largely attributed to the difficulty of classifying physical activity as moderate, hard or very hard. Reclassification of the activity data is in progress. This study indicates that the EE of a population, as small as 24, can be determined from 7-day physical activity records.

Key nutrition and health problems identified in the Lower Mississippi Delta as assessed from the Foods of Our Delta validation and pilot study. Consumption of high fat foods and fast foods were seen as the most important nutrition problems, and hypertension and teen pregnancy as the most important health problems. Multiple contributing factors to health and nutrition problems were reported including poverty, lack of exercise, lack of nutrition and health knowledge and inadequate health insurance. Findings from the Foods of our Delta validation and pilot study showed that calories, protein, and number of food items were similar whether interviews were completed by telephone or in-person. There were no differences in dietary data collected from telephone and non-telephone households.

The National Food and Nutrient Analysis Program (NRNAP). As part of NRNAP, various new cooperative agreements and an MOU with the NASS have been able to apply the statistically based conceptual framework for the selection of representative samples of the food supply; develop unique sampling plans for specific foods and nutrients; and to chemically analyze food samples for nutrient content under rigorous quality control programs. More than 100 foods representing more than 10,000 sample units collected from 24 locations nationwide have been analyzed.

Rapid method for determination of selenomethionine in foods and dietary supplements developed. There is a mandate for developing techniques to determine food components and establish food composition databases. Dietary selenium can have both beneficial and toxic effects, occurring in both inorganic and organic forms. One important organic form, selenomethionine, is the analog of the sulfur amino acid methionine. A stable isotope dilution method was developed for the rapid determination of selenomethionine in foods and dietary supplements. One important finding using this method is that food label claims for added selenium in the form of selenomethionine are not always accurate. This highly accurate and precise method should have a significant impact in providing the necessary tools to facilitate monitoring of the accuracy of labeling claims for selenomethionine in dietary supplements.

Methods developed which simplify analysis of beta-carotene and vitamin A. Understanding the metabolism of carotenoids in foods requires detailed analytical procedures which can measure both natrually occurring and labeled compounds. The stable-isotope methods incorporated liquid chromatography separation and mass spectrometry detection and characterization. These procedures will greatly enhance the ability to determine the conversion of beta-carotene to vitamin A and the physiological parameters that affect this conversion.

Modified dietary fiber method for determination of resistant starches. Food composition data on starches that are neither digested nor absorbed by humans is lacking. A dietary fiber method was modified for the determination of resistant starches in muffins containing starch with different amounts of amylose, amylopectin, and oatrim. Results indicated that the formation of resistant starch in baked products is proportional to the relative amount of high amylose corn starch used in the recipe. A more refined and robust method will enable other food analysts to determine resistant starch routinely for clinical and nutritional studies.

Nutritional status at a very early age may have a major impact on cognition and brain function. Children with suspected nutrition deficits as infants were shown to exhibit a greater range of emotion on temperament scales, have more toys in the home, and have lower plasma ferritin, calcium, sodium, and magnesium levels. When these children are older, the data suggest that they are deficient in academic skills, i.e. symbol search, IQ, reading, arithmetic, and longer latencies on the right side of their brains than on the left side in tasks which compare the recognition of congruent works with anomalous letters (pattern recognitions). This later error can translate into deficiencies with acquisition skills, such as language acquisition.

Adequate iron status is required to maintain optimal cognitive performance. It was previously shown that energy restriction impaired iron status in women which in turn was associated with the inability to concentrate. Since it was not known if this was gender specific, the relationship between iron status and cognitive function in healthy men was studied. It was found that the inability of men to concentrate on a task was associated with an elevated iron status depletion rate, which concurred with the prior results for women. Thus, it appears that adequate iron status is required to maintain optimal cognitive performance on attention-based tasks in both men and women.

Health benefits of conjugated linoleic acid (CLA) may differ between rats and humans. Animal models have shown that CLA has numerous health benefits. It is not known if CLA has similar health benefits in humans. A human study was conducted in which adult females were given 3 gm CLA per day for 60 days. Preliminary results indicate that there was no significant effects on the physiological parameters that are known to be affected in animal models. These results could mean that CLA has to be fed to humans for longer periods or to young subjects. Another interpretation would be that due to species differences CLA has no beneficial effects in humans.

Extracellular zinc superoxide dismutase activity may be a sensitive and specific marker of zinc status. Assessment of zinc nutrition status is complicated by the availability of blood biochemical markers that clearly distinguish between adequate and deficient zinc status and differentiate between degrees of zinc status, marginal and severe deficiency states. The response of a zinc-containing enzyme in plasma, extracellular superoxide dismutase, in a series of studies of rats fed different amounts of dietary zinc and zinc-deficient rats supplemented with zinc was studied. The activity of this enzyme was found to be more responsive to differences in dietary zinc, particularly in the rehabilitation of the zinc-deficient rats, than the currently used biochemical indicators of zinc status, including plasma zinc. This marker may be useful in assessing human zinc nutrition status among individuals.

Mathematical model of nickel metabolism developed. By the use of the isotope nickel-63, it was found that 2.5% of nickel ingested is absorbed and very little is retained in rats. A model was developed which suggests that nickel is homeostatically controlled by absorption and retention processes, and that tissue nickel is metabolized by at least three different mechanisms. The model and findings provide further evidence that nickel is an essential element for laboratory animals and thus, is most likely important for human health.

Changes in dietary fat can modify mineral metabolism. The effect of consuming a diet rich in saturated fat (animal fats tend to be more saturated) compared to a diet rich in polyunsaturated fat (vegetable fats tend to be more polyunsaturated) on mineral metabolism was investigated in 11 pre-menopausal women consuming diets either low or high in dietary manganese. Consumption of the diet rich in polyunsaturated fats significantly increased plasma ionized calcium, ionized magnesium and total magnesium concentrations and significantly decreased plasma iron concentration and transferrin saturation.

Body adaptations variable to changes in iron intake. Iron intakes in the U.S. have increased because of increased fortification of foods and use of nutrient supplements. A study was conducted to determine how well men and women adapted to supplementation with 50 mg iron daily for 12 weeks. An increase in iron stores with supplementation persisted for 6 months only in men and women with iron stores that were already adequate to high, but not in those with low iron stores. These results indicate that people with adequate iron stores do not fully adapt to prevent increased iron stores with supplementation, but that women with low iron stores may need continuing iron supplementation to counterbalance high rates of iron excretion.

Requirement for dietary choline is partly dependent on the folate intake. Choline is a nutrient that is needed for growth of healthy cells and production of the neurotransmitter, acetylcholine. Choline can substitute for folate in some biochemical reactions. The body can make its own choline, but studies have shown that the body could not make enough choline when dietary folate and choline intakes were low, probably because choline was being used to make up for the lack of folate in the diet. This has been shown in post-menopausal women and similar results have been found in adult men. These data contributed to recent decisions to double the RDA for folate from 200 to 400 micrograms/day and to recommend for the first time an Adequate Intake for choline of 425 and 550 mg/day for women and men, respectively. The findings also raise the converse question of whether the dietary requirement for folate may depend on choline intake. This has potentially great significance in that the recent doubling of the folate RDA, and the Food and Drug Administration (FDA) mandate to fortify U.S. grain products with folic acid, stems from the newly recognized roles of folate in preventing neural tube birth defects and elevated blood homocysteine levels (a risk factor for heart disease). So the body's folate status may depend not only on how much folate, but how much choline we consume. These findings provide another example of the benefits of eating a variety of foods, because folate is found in plant foods and choline is found in high protein foods such as meats and dairy products.

Association between dietary magnesium and potassium. An association between dietary magnesium and potassium, and fruit and vegetable intakes and bone mineral density in the original Framingham elder cohort was identified. These foods and nutrients were associated with bone mineral density among both men and women and significantly predicted lower bone loss over a four year follow-up among men. These results support the hypothesis that alkaline-producing dietary components contribute to bone maintenance.

Established the isotope dilution technique for vitamin A. The vitamin A requirement in elderly people is uncertain. The usefulness of the deuterated retinol dilution test in providing quantitative estimates of total body stores of vitamin A in elderly Guatemalans as a means to estimate vitamin A requirements was examined. It was shown that the isotope dilution technique for estimating total body reserves of vitamin A provides important information of vitamin A status. It was also shown that elderly Guatemalans have fully satisfactory vitamin A status and that shorter times for partial equilibration of labeled vitamin A with endogenous reserves may provide adequate estimates of total body reserves in humans. This study has established the isotope dilution technique for vitamin A assessment as a gold standard for determining vitamin A stores.

Vitamin E improves immune response. Consuming as much as 800 IU/day of vitamin E for 6 months had no adverse effect in healthy elderly, but significantly improved their immune response. It was shown that one means by which supplemental intake of vitamin E contributes to the reduction of the risk of atherosclerosis and cancer is through modulation of immune and endothelial cell interaction, production of several chemokines, including IL-8 and MCP-1, pro-inflammatory cytokine IL-6, and modulation angiogenesis. This inhibitory effect of vitamin E on suppression of monocyte adhesion to endothelial cells was also observed with lycopene, which is abundant in tomatoes and tomato products. Green tea flavonoids showed similar but more potent inhibitory effects on angiogenesis compared to that observed with vitamin E.

Degree of hydrogenation of oil determines the effect on low density lipoprotein (LDL). Different forms of dietary fats, such as butter and soybean oil, with varying degrees of hydrogenation, as compared to the pure unhydrogenated oil were examined in 36 men and women consuming diets containing these fats. Subjects who consumed butter had the highest levels of low density lipoprotein (LDL) cholesterol, followed by those who consumed a heavily-hydrogenated margarine. The degree of hydrogenation determined the effect on LDL. Those who consumed soybean oil had the lowest LDL cholesterol and the best ratio of total cholesterol to HDL These data suggest that the use of the oil or very soft margarine is preferable to hydrogenated margarine or butter, in achieving optimal lipoprotein levels.

Long-term vitamin C intake may reduce risk of cataracts. Persons with intake of vitamin C supplements for over 10 years had a marked reduction in risk for lens nuclear opacities. Intake of many other nutrients was associated with risk for lens nuclear opacities. Most of these correlations were not independent of the association between vitamin C supplement intake and risk for cataract. These data clearly indicate the benefit of maintaining a diet rich in vitamin C (antioxidants) early in life, to limit the risk for eye disease later in life.

Key role of dietary amino acids in intestinal energy metabolism. The results of animal studies show that the overwhelming source of energy for the developing intestine of the milk fed neonate is dietary protein and that the mucosa appears to be capable of oxidizing nutritionally essential amino acids. Glucose utilization at this site is directed to biosynthesis rather than oxidation. The intestinal utilization of nonessential amino acids as energy sources appears to be obligatory while essential amino acid catabolism varies with intake. Parallel investigations show that skeletal muscle metabolism is very plastic and will readily interchange lipid and carbohydrate as sources of energy. In vivo studies of fuel selection in the mucosa of young pigs have also confirmed the key role of dietary amino acids in intestinal energy metabolism, even under conditions of restricted protein supply. The results also suggest that systemic glucose serves a biosynthetic rather than an oxidative role in the intestine.

Energy requirements of very young children lower than current recommendations for intake. From birth to 2 years of age the energy requirements were found to be 15-27% lower than current recommendations for energy intake. Adjusted for weight, total energy expenditure and energy requirements differed by feeding group (breast-fed < formula-fed), but not by age or gender. Differences in body composition between feeding groups were seen during early infancy, but did not persist into the second year of life.

Supplementing breast-fed mothers with docosahexanoic acid (DHA) not effective. DHA is a fatty acid which is an important component of the retina and is virtually the only fatty acid of its type present in the brain. Human milk contains DHA but formulas currently sold in the U.S. do not. In addition, the amount of DHA in human milk varies depending on the diet of the mother. It was shown that breast-feeding mothers supplemented with DHA for 4 months after delivery did not improve visual function or neurological development of the infants despite a doubling of milk DHA content and a roughly 50% increase in infant plasma DHA.

Benefit of human milk feeding. It is important to better understand factors that affect gastrointestinal growth and adaptation. It was shown that human milk feeding accelerates gastrointestinal development more than feeding with formula. Human milk feeding is associated with less infectious complications than formula feeding.

Another role for lipoprotein lipase. Documented that a mutation in the lipoprotein lipase gene is associated with increases in low density lipoprotein cholesterol but not in high density lipoprotein cholesterol or triglycerides.

Nitric oxide synthase also elevated in copper deficiency. A previous study had shown that the concentrations of two important chemical messengers, nitric oxide and cyclic GMP, are elevated in copper-deficient hearts, which suggested their possible role in reduction of heart contractile force in copper deficiency. In a follow-up study this past year it was shown that the amount of one of the enzymes that produce nitric oxide, inducible nitric oxide synthase, is also elevated in copper deficiency, which suggest an elevated genetic expression of this enzyme. These studies help to define the molecular basis for impaired heart function when dietary copper is restricted and illustrate the dependence of good cardiovascular health upon adequate dietary copper.

Hemochromatosis can be modeled by mice with a mutation in beta-2 microglobulin. Hemochromatosis, a genetic human disease of excessive liver iron accumulation, can be modeled by mice with a mutation in beta-2 microglobulin and studying these mice can help in the understanding of the body's control of iron stores. Dietary iron absorption and retention were measured in mutant and control mice. Mutant mice accumulated more iron in the liver without greater intestinal iron uptake or greater total body iron retention. These results indicate that high liver iron in hemochromatosis may be at least partially because of an abnormality in the tissue distribution of iron, rather than just an abnormality of iron absorption or excretion.

Vitamin K may be a modifiable risk factor for osteoporosis. Researchers evaluated associations between dietary vitamin K intake, apoE genotype, bone mineral density and rate of hip fracture among elderly men and women participating in the original cohort of the Framingham Heart Study. Low vitamin K intakes were significantly associated with increased incidence of hip fractures in men and women. In contrast, neither low intakes of vitamin K nor apoE4 allele were associated with low bone mineral density. These findings suggest that dietary vitamin K may be a modifiable risk factor for osteoporosis.

Vitamin D receptor genotype in premenopausal women is not related to bone turnover. Women who carried polymorphisms in the vitamin D receptor gene were fed a low calcium diet. These polymorphisms, previously seen in another study, were associated with low and high bone mineral density. These results are important because it suggests that the differences in bone density observed between these groups of women is not related to differential changes in bone turnover subsequent to consuming inadequate calcium intakes. Thus, the genesis of genotype-specific differences in bone mineral density are likely to reside elsewhere, which will be the basis of future study.

Substrate specificities for maltase and starch documented. The sequencing of the cDNA of maltase-glucoamylase and its expression in mammalian cells to document the substrate specificities for maltase and starch were completed. A 3.5 month old infant with failure to digest starch oligomers, the specific substrate for maltase-glucoamylase was discovered. The infant has a point mutation C1673T which translates to S542L mutation 12 amino acids downstream from the N-terminal catalytic site. This mutation is present in genomic DNA from the child and mother. The functional nature of this mutations is now being tested. This may be the first case of congenital starch malabsorption to be studied at the molecular level.

Dietary supplementation is more effective in inhibiting low density lipoprotein (LDL) oxidation. Enrichment of LDL with beta-carotene by supplementation of the diet protected LDL from oxidation. However, enrichment with another major carotenoid in the diet (and in plasma), namely lycopene (achieved by ingestion of tomato juice), had no effect on cell-mediated oxidation of the LDL. By studying the impact of enriching lipoproteins with carotenoids by dietary supplementation and comparing this method with the in vitro enrichment methods previously developed, this study clearly showed that dietary supplementation is more effective in inhibiting LDL oxidation than is in vitro enrichment. These results show that in vitro supplementation methods are not appropriate for studying the impact of carotenoid content of lipoproteins on their oxidation.

Less toxicological risk from selenium found in broccoli. Broccoli may contain a unique and beneficial form of selenium but little is known about its metabolism. Rat studies showed that selenium from broccoli accumulated slower and did not increase selenoprotein enzyme activity as well as other forms of selenium. Because these studies indicated that the selenium from broccoli may not pose as much of a toxicological risk as other forms of selenium and may be a means of supplementing selenium, a study was conducted to determine how humans metabolize selenium from broccoli. Growing broccoli was loaded with a stable isotope of selenium and then fed to humans. Selenium from broccoli did not accumulate in the plasma as much as selenium from a salt, but less was excreted in the urine. These results indicated that selenium from broccoli may not pose much of a toxicological risk to humans because it does not accumulate in tissues to the extent that other forms of selenium do.

Antioxidant capacity of oats. The antioxidant capacity of oats and oat subfractions were determined in vitro through their protective potential against oxidative damage to human lipoproteins and a target protein molecule. The potency of this effect appears mediated through polar phenolic compounds in addition to the vitamin E content of oats. Phytochemical antioxidants may promote health and reduce the risk of several chronic diseases. Further study in animal models and humans is now warranted.

Blueberry supplementation beneficial to rats. Rats supplemented with blueberries showed the greatest reversal of age-effects on nearly all of the parameters examined and was especially effective in reversing motor behavioral deficits as compared to spinach or strawberry supplementation. The most common neuronal changes that occur in aging are expressed as correlative motor and cognitive behavioral deficits. Little is known about the mechanisms involved in these age-related declines in cognitive and motor behaviors and even less is known concerning the nutritional modulation that could be employed to retard or reverse these declines.

Factors in soy protein isolate may reduce the incidence of breast and colon cancer. Data from rat studies suggest that soy protein isolate, the sole protein source of most soy infant formulas, can reduce the incidence of breast cancer and colon cancer, and can improve metabolism. The rats have leaner body composition, greater metabolic capacity towards xenobiotics such as medications and carcinogens, 25% lower risk of developing chemically-induced breast cancer, and 80% lower risk of developing chemically-induced colon cancer. Similarly, a modified version of the common whey protein found in milk can provide even more protection against breast cancer and also protect against colon cancer.

Iron uptake by intestinal epithelial cells is enhance by factors in meat. A factor in fish that promotes iron absorption has been isolated. Complete identification of this so called 'meat factor' may lead to the development of improved dietary iron and contribute to improved nutritional health because of improved iron bioavailability. This is important because about 30% of the world's population is iron deficient and there are numerous adverse physiological consequences due to low iron status.

Iron stores are a primary determinant of the amount of manganese absorbed from a meal. Thirty human volunteers with low or high stores of iron were fed diets that supplied high or low amounts of manganese. This study demonstrated that iron stores are a primary determinant of the amount of manganese absorbed from a meal, but retention of manganese was regulated independently of absorption by means of variable excretion. These results show the need to consider the iron stores of a human when attempting to determine the optimal intake of manganese.

Physiological concentrations of zinc significantly reduced the transport rate of copper across the intestinal cell monolayer. The physiological concentrations of zinc, similar to those in the gut after a meal, was shown to significantly reduce the transport rate of copper across an intestinal cell monolayer, apparently by reducing the relative abundance of the product of a specific gene involved in copper transport. This finding will further advance the understanding of the mechanisms of absorption of the important nutrient copper, and what dietary factors affect this process.

Intestinal ferritin production may indicate how body adapts to adjust iron absorption. Fecal ferritin excretion was measured in iron supplemented and control subjects. The results provide new information on the variability of ferritin excretion in a free-living population and indicate that the intestine rapidly increases or decreases ferritin production in response to increased or decreased dietary iron, consistent with adaptation that was observed in nonheme, but not heme iron absorption. Fecal ferritin observations will help us understand the intestinal control of iron absorption, and differences in the control of heme and nonheme iron absorption.

Molybdenum is highly available from kale and less so from soy. Molybdenum is highly available when added to the diet, but nothing was known about bioavailability of molybdenum from foods. Soy and kale were labeled with stable isotopes of molybdenum for use in a human study. The study showed that molybdenum is highly available from kale, but less available from soy. These results indicate that the bioavailability of molybdenum must be taken into account when establishing dietary recommendations.

*Intervention is a cross-cutting area of research and several of the studies listed above could also be a part of this component.