Introduction

The occurrence of overweight and obesity has increased remarkably in the U.S. since the late 1970's, for both children and adults.  Although obesity research is only a part of the comprehensive food-based Human Nutrition Research Program in ARS, within the past year several obesity-related activities occurred at the ARS Human Nutrition Research Centers and locations.  Some of these activities are presented below.

The forty-five-member National Agricultural Research Extension, Education and Economics (NAREEE) Advisory Board visited the Agricultural Research Service’s (ARS) Beltsville Human Nutrition Research Center (BHNRC), Beltsville, MD on October 27, 2003, as part of their meeting and new member orientation.  The Board had an opportunity to see the BHNRC’s new Human Study Facility, meet its’ management team, and learn about its’ multi-disciplinary research program that offers strengths in both applied and basic nutrition research for assessing the impact of diet and physical activity on human health.  Factors influencing obesity were discussed, including what people eat in the U.S., the influence of the community and environment, and the importance of understanding energy balance, energy in and energy out.  The discussion brought out a valuable exchange of ideas on how the issues of obesity prevention could be studied and what it will take to solve the problem.

A joint meeting was held at the ARS, BHNRC by USDA Mission Area Representatives from Research, Education and Economics (REE) and the Food Nutrition Consumer Service (FNCS) on October 30, 2003 to discuss obesity prevention.  USDA Agencies represented included Agricultural Research Service (ARS), Economic Research Service (ERS), Cooperative State Research Education and Extension Service (CSREES), Center for Nutrition Policy and Promotion (CNPP), and Food and Nutrition Consumer Services (FNCS).  The charge given by Under Secretaries Joseph Jen and Eric Bost was to examine the issue of obesity prevention and what the USDA Agencies can do together to affect this challenge for a healthier U.S. population.  Presentations were made by representatives of each Agency, focusing on work being done on obesity prevention.  Discussions centered on opportunities for collaborative studies.  The Under Secretaries left the attendees with the charge to discuss and formulate a plan for working together in the area of obesity prevention.

On June 18, 2003 the ARS Human Nutrition Research Center on Aging (HNRCA) in Boston, MA hosted a symposium entitled “Understanding Methods in Obesity Research” sponsored by The Boston Obesity Nutrition Research Center (BONRC).  BONRC is a National Institutes of Health (NIH) funded obesity nutrition research center representing a collaboration of most Boston area institutions that conduct obesity and nutrition research including the HNRCA, The Tufts School of Medicine, Boston Medical Center, the Beth Israel Deaconess Medical Center, the Joslin Diabetes Center, Children’s Hospital, and the Massachusetts General Hospital.  The symposium was designed to introduce students and junior investigators to methods used in obesity research, and to help clinicians better understand the growing body of obesity literature in medical journals. The conference was focused on providing a basic understanding of methods, as this is frequently overlooked in lieu of presenting research findings.  The faculty was drawn from all the participating BONRC institutions.  Topics included measurement of energy expenditure, body composition, insulin sensitivity, use of dietary surveys and questionnaires, an introduction to the role of genetic testing in clinical research, and assessment of compliance with dietary interventions.  More than 150 people attended the symposium.  Because of very positive feedback on the value of the symposium, the BONRC will offer this symposium on a yearly basis.  Other institutions, including the Massachusetts Medical Society, have expressed interest in helping to support this highly successful event in the future.

Exploring the suggested link between socioeconomic status, diet quality, food intake behavior, and obesity in the U.S. was the topic of a workshop hosted by the Western Human Nutrition Research Center in Davis, CA on April 30, 2003.  The workshop was designed to bring together experts from academia and government to discuss the obesity epidemic in the U.S. and to examine, from multiple perspectives, the apparent link between food insecurity and obesity.  Presentations on the effects of economic, sensory, psychological, life-course, and early developmental factors on food intake and eating behavior provided provocative ideas and insight into the complex relationship between obesity and food insecurity.  Moderators for panel discussions, held after the series of scientific presentations, included: Eric Bost, USDA Under Secretary for Food Nutrition Consumer Services; Rodney Brown, Deputy Under Secretary for Research, Education and Economics; William Dietz, Director, Division Nutrition and Physical Activity, Centers for Disease Control and Prevention; and Susan Forester, California Department of Health Services.

Nutrient Requirements

Doubly deficient diet causes loss of natural resistance to viral infection.   Scientists at the Beltsville Human Nutrition Research Center (BHNRC) in Beltsville, MD have shown that mice, known to resist infection with a heart-damaging coxsackievirus, become susceptible to the virus when fed a diet deficient in the antioxidant micronutrients, vitamin E and selenium, or when conditions of iron overload are applied to a mouse that is vitamin E deficient.  These results demonstrate the powerful influence of low antioxidant nutritional status on the course of viral infection in the host.

Selenium plays a two-fold role in proper heart function.  It is known that poor selenium status can increase the virulence of viruses known to attack heart muscle (Coxsackie viruses).  Now, ARS researchers at the BHNRC in Beltsville, MD, in collaboration with scientists at the University of Buenos Aires in Argentina, have found that heart muscle contracts less forcefully in mice fed a selenium-deficient diet.  Selenium deficiency appears to put the heart in double jeopardy, first by decreasing the ability of the organ to contract forcefully, and second by increasing the virulence of a pathogen known to attack heart muscle.

Copper deficiency increases the risk for heart disease.  Studies conducted by researchers at the Grand Forks Human Nutrition Research Center (GFHNRC) in Grand Forks, ND found that the hearts of copper-deficient mice exhibited reduced maximum contractile pressure, diminished excitation by adrenaline, increased pressure during relaxation, and elevated collagen deposits. All of these factors are signs of heart failure.  This research suggests that dietary copper deficiency may be a risk factor for heart disease and subsequent cardiac failure in humans.

Boron may improve insulin function.  Dietary boron, found notably in fruits, vegetables, nuts and legumes, might help reduce the amount of insulin needed to maintain normal blood glucose levels.  Studies with rats by scientists at the GFHNRC in Grand Forks, ND demonstrated that a diet supplemented with boron reduced blood insulin levels without affecting blood glucose concentration. This suggests that dietary boron may protect insulin-secreting cells from exhaustion and thereby help to prevent diabetes mellitus.

B vitamins may reduce the risk for congestive heart failure.   High blood homocysteine is a known risk factor for atherosclerotic disease.  Now ARS scientists at the Human Nutrition Research Center on Aging (HNRCA) in Boston, MA have found a direct association between elevated blood homocysteine and congestive heart failure.  Increasing folic acid and other B vitamins in the diet reduces blood homocysteine.  Congestive heart failure could in part be prevented by proper vitamin nutrition.

Vitamin D requirements may increase with age.  The blood level of 25-hydroxyvitamin D is the best measure of vitamin D status but there is no consensus on its optimal level for bone health. Scientists at the HNRCA in Boston, MA examined the relationship between 25-hydroxyvitamin D blood levels and hip bone mineral density in Caucasian, Hispanic, and African American men and women, aged 20 to 90, who participated in the National Health and Nutrition Examination Survey (NHANES) III survey.  Bone mineral density increased as 25-hydroxyvitamin D levels increased in all ethnic groups.  However, in Caucasian men and women between the ages of 20 to 50 years, bone mineral density increased as 25-hydroxyvitamin D levels rose 50% above the upper end of the recommended reference intake range. These findings suggest that for optimal bone health, intakes of vitamin D above those usually recommended may be needed.

Early developmental affects of fatty acids on brain structure is critical.

Scientists at the Children's Nutrition Research Center in Houston, TX, with collaboration from the Hermann Eye Center, University of Texas Health Science Center at Houston, and the Meyer Center for Developmental Pediatrics, Texas Children's Hospital, conducted studies to determine if the intake of a specific fatty acid during early infancy affects visual and neurodevelopmental outcome.  These brain functions are crucial for development of motor skills.  By increasing the maternal fatty acid supplementation of the mothers' milk, there remained no difference in the visual perception between groups at 4 or 8 months of age, and there were no differences between groups in any of several neurodevelopmental indices at 12 or 18 months of age.  However, at 30 months of age, children whose mothers received the maternal fatty acid supplementation 4 months before birth were higher than that of children whose mother received a placebo. This finding suggests that fatty acid availability during the first 4 months of life has undefined immediate effects on brain structure and/or function that are important for subsequent motor development.

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

Eating out is a major predictor of obesity for adults.  ARS researchers at the HNRCA in Boston, MA, in collaboration with Framingham Heart Study investigators, found that the frequency of eating out and dietary variety are the two strongest predictors of excess body fat in healthy adults.  These findings help emphasize the central role of diet in the development of body weight problems and suggest specific strategies for obesity prevention.

Eating without hunger is a behavioral predictor of childhood obesity in some Hispanic Americans.  Preliminary results from a study conducted by scientists at the Children’s Nutrition Research Center (CNRC) in Houston, TX revealed that eating in the absence of hunger is a major factor underlying childhood obesity in the Texas Hispanic population. On average, nearly 20% of these children’s total daily energy intake came from eating foods when not hungry and those with high eating without hunger scores were twice as likely to be overweight. Understanding eating behavior is essential to reducing the incidence of childhood obesity.

Women dieting on their own exhibit increased stress and diminished mental performance.  ARS scientists at the WHNRC in Davis, CA, in collaboration with researchers at Aston University in the United Kingdom, have shown that overweight women dieting on their own have more mental stress, as measured by salivary cortisol, and a poorer ability to concentrate than women receiving support from a structured weight loss program. This underscores the importance of devising appropriate weight loss strategies without functional consequences.

Dietary conjugated linoleic acid (CLA) controls synthesis of hormones important for body weight regulation.   Investigators at the WHNRC in Davis, CA, working with mice showed that certain forms of CLA cause a several fold reduction in messenger RNA levels for the two hormones, leptin and adiponectin. These hormones are important in the regulation of body fat and carbohydrate metabolism.  This research suggests a possible mechanism by which CLA helps reduce body fat and may have implications for obesity prevention.

Risk for atherosclerosis due to diet-gene interactions more prevalent in African- and Hispanic Americans, and other minority groups.  Researchers at the HNRCA in Boston, MA, in collaboration with Framingham Heart Study scientists, studied a gene (LIPC) involved with removal of excess cholesterol from the body by regulation of the protective good cholesterol (HDL).  People carrying the CC form of this gene reacted to high fat diets by increasing their blood HDL levels (desirable response), whereas those with the TT form showed decreased blood HDL levels (undesirable response).  Although the TT form is common in Caucasians it is more prevalent in African and Hispanic Americans and other minority groups.  This information helps to identify segments of the population particularly susceptible to diet-induced atherosclerosis.

The selenium-containing enzyme thioredoxin reductase may help control oxidative stress.  Selenium is a component of several antioxidant enzymes some of which may have cancer-protective effects. At the GFHNRC in Grand Forks, ND, reporter gene constructs of the selenium-containing enzyme thioredoxin reductase were inserted into human liver cells and incubated with oxidative stress protective compounds. Reporter genes were activated in a manner that suggests the presence of a regulatory gene sequence called the antioxidant responsive element (ARE); mutation and gel shift analysis confirmed the presence of this sequence. This study demonstrates the selenium-containing enzyme thioredoxin reductase is part of a large family of genes that are coordinately regulated in conditions of oxidative stress by the ARE.  Thus, thioredoxin reductase may help decrease oxidative damage-induced carcinogenesis.

Cancer-protective effects of soy proteins demonstrated in animal studies.  Scientists at the Arkansas Children’s Nutrition Center (ACNC) in Little Rock, AR, found that feeding soy protein isolate to rat dams during pregnancy and lactation provided protection against the development of colon tumor precursor lesions in the offspring. Dietary soy protein isolate stimulated the expression of 48 and inhibited the expression of 81 rat colon genes.  Further, it was found that consumption of soy protein isolate during development inhibits metabolic activation of common procarcinogens in rat liver and mammary gland.  Soy protein isolate inhibited the expression and induction of cytochrome P450 enzymes in the CYP1A and 1B families.  These enzymes are known to activate carcinogens to mutagenic metabolites and reduce DNA adduct formation in target tissues. These results suggest mechanisms by which soy consumption may be protective against certain forms of cancer.

Resistance strength training improves diabetes control. Researchers at the HNRCA in Boston, MA, found that 16 weeks of progressive resistance training resulted in skeletal muscle hypertrophy of both type I and type II muscle fibers in older individuals with poorly controlled diabetes. Supervised and safe resistance training improved performance-based physical function and muscle strength and improved glycemic and metabolic control. This provides the first direct demonstration of a relationship between muscle fiber morphology, insulin-stimulated glucose uptake, and resistance training in skeletal muscle of untrained older adults with poorly controlled diabetes. With the high prevalence of diabetes in the elderly, searching for effective ways to improve metabolic control is crucial to reduce their burden of disease.

Elderly are more susceptible to morbidity and mortality from viral infections.  When the non-virulent Coxsackie virus B3 is passed through an antioxidant-deficient host it mutates to a virulent form known to attack the heart muscle.  Investigators at the HNRCA in Boston, MD, have shown that passing this virus through an older host can also result in permanent, adverse mutations, making the virus more deadly to future hosts.  This may in part explain why the elderly have a higher incidence of severe viral infections.

Detecting and localizing genetic factors that influence childhood obesity.. Scientists at the Children's Nutrition Research Center in Houston, TX, initiated a 5-year study, with the primary goal to detect and localize traits that impact childhood obesity using a genomic scan of Hispanic children. Phenotyping children includes human body measurements and body composition, as well as factors associated with the development of obesity: energy partitioning during growth, energy expenditure, physical fitness and activity, hormones, metabolites and neurotransmitters; phenotyping has been completed on 227 Hispanic families, including 448 parents and 725 children. Childhood obesity is clearly a familial disease, and since families share not only genes, but also diet, cultural background and many aspects of lifestyle, this study will enhance our ability to detect traits associated with obesity and allow us to divide this familial trait into its genetic and environmental components.

Nutrition Monitoring

“What We Eat in America Survey”.  Dietary methodology validation study completed.  Researchers at the BHNRC in Beltsville, MD, have completed the data collection phase of an extensive, biomarker based, validation study of the new USDA Automated Multiple-Pass Method (AMPM), the quantitative food intake method used in the national survey.  Results will provide a scientific assessment to ensure the AMPM method collects complete and accurate 24-hour dietary recalls.   In this era of escalating obesity in the U.S., accurate food consumption information is key to understanding dietary behaviors contributing to the obesity epidemic.

Potential adverse effects of folic acid fortification require further study.  In 1997 - 98, the FDA instituted folic acid fortification of cereal grain products in the U.S. to reduce the incidence of neural tube birth defects. Scientists at the HNRCA in Boston, MA, and investigators from the Framingham Heart Study assessed the impact of folic acid fortification on the dietary intakes of U.S. adults. They found that on average folic acid intakes are nearly double that which had been projected to occur with food supply fortification.  Further, they observed that folic acid intakes for adults are now more frequently exceeding the Upper Limit (UL) of recommended intakes. Given limited evidence on adverse health consequences of high folic acid intakes, this work suggests a need for further research to determine if detrimental health effects accompany elevated folic acid intake levels.

Composition of Foods

USDA’s food composition database is now available for personal digital assistants, personal computers and web-based applications.  Scientists at the BHNRC in Beltsville, MD, released USDA’s National Nutrient Database for Standard Reference in several new formats to increase access and utilization of this valuable national resource by both the scientific community and general public.  This significant technology transfer advance was made possible through a Cooperative Research and Development Agreement between the USDA, Nutrient Data Laboratory (NDL), Beltsville, MD and HealtheTech Inc., Golden, CO.  The new software products contain USDA’s food composition data for more than 6200 foods and 30 to 80 nutrients and/or food components.  In June 2003, the Office of the Secretary of Agriculture recognized the importance of this advancement through presentation of a USDA Superior Service Award.

The software releases can be obtained at the NDL website at www.nal.usda.gov/fnic/foodcomp. 

Flavonoid content of fruits, vegetables and nuts.  Fruits, vegetables, and nuts contain numerous flavonoid compounds believed to reduce the risk of cancer and cardiovascular disease.  Researchers at the BHNRC in Beltsville, MD, in collaboration with the Produce for Better Health Foundation measured 27 flavonoids in 50 commonly consumed fresh fruits, vegetables, and nuts.  This is the first systematic compilation of quantitative data for flavonoids in these foods and will be publicly released as a provisional database.

Proanthocyanins determined in infant foods, fruits, and vegetables.  Scientists at the ACNC in Little Rock, AR, and at the BHNRC in Beltsville, MD, developed new methods to determine the content of proanthocyanidins in fruits, vegetables, and infant foods.  This is the first report on the concentration of these compounds in a comprehensive group of foods and will become part of the USDA’s National Nutrient Database.  Epidemiologists and other researchers can now study relationships between these antioxidant components and health outcomes in children and adults. 

 Genetic diversity of legume seeds.  Although they are an important source of protein, energy and mineral nutrients, little is known about the genetic diversity for these nutritional components in many food legumes. Scientists at the Children's Nutrition Research Center in Houston, TX, in collaboration with the USDA/ARS Western Regional Plant Introduction Station, have characterized seed mineral and protein concentrations in 485 genotypes of pea and have entered all data into the Germplasm Resources Information Network (GRIN). They demonstrated that mineral concentrations varied as much as 10-fold across the various pea types, and protein concentration varied over two-fold. This pea genetic diversity information will be an important resource for plant breeders, plant physiologists, human nutritionists, and food scientists, and will ultimately contribute towards an improved food supply for U.S. consumers.

Health Promoting Intervention Strategies for Targeted Populations

Food insecurity is a cause of depression in Northern Plains Indians.  By building  relationships between regional American Indian communities and the USDA, scientists at the GFHNRC in Grand Forks, ND, developed and evaluated culturally appropriate research methods and used the new methodology to characterize relationships between health, nutrition and social factors in the Northern Plains Indians.  Research data was collected using a mobile research laboratory at powwows and health fairs.  It was found that depression in this population group is strongly related to food insecurity.  Associations also existed between depression and low exercise, high body mass index, and poor physical health and diet, all moderated by gender.  Future studies are planned to further evaluate the impact of diet and physical activity on health issues endemic to American Indian communities.  The overall goal is to formulate and implement effective and culturally appropriate interventions to improve health and quality of life in the American Indian population.

Community input is essential to formulating effective dietary interventions.  Scientists with the Lower Mississippi Delta Nutrition Intervention Research Initiative (Delta NIRI), Little Rock, AR, collaborated with several community research groups in each of three Lower Mississippi Delta communities (Marvell AR, Hollandale MS, and Franklin Parish LA) to identify the top three food and nutrition related problems in each community.  Comprehensive Participatory Planning and Evaluation (CPPE) was the process employed.  Results will guide the development of culturally appropriate nutrition intervention studies for the Mississippi Delta region.  This underscores the importance of empowering community people by involving them in all planning and evaluation aspects of the intervention research process.

Factors that mediate food choices in low income, at-risk children in the Lower Mississippi Delta.  Scientists at The University of Southern Mississippi, a consortium partner of the Lower Mississippi Delta NIRI, developed and tested new instruments to measure and evaluate factors that mediate food choices in low income, at-risk children in Mississippi.  Evaluating behavioral constructs such as peer influences, self-efficacy to choose healthy foods, and behavioral capabilities, can lead to a better understanding of the adaptive changes children experience when adopting new and healthier food choices.  This research targets the role of food choices in the development of childhood obesity.

Eating patterns were associated with cardiovascular risk factors in young adults. Cardiovascular disease is the dominant killer in the United States. Scientists at the Children's Nutrition Research Center in Houston, TX, and the Bogalusa Research Team, analyzed whether eating patterns were associated with cardiovascular risk factors in young adults. A low-fat eating pattern was inversely associated with waist-to-hip ratio and positively associated with HDL-C; a high-fat, high sugar-eating pattern was positively associated with waist-to-hip ratio and negatively with HDL-C. Efforts to prevent cardiovascular disease among young adults should target low-fat eating practices and a person's waist to hip ratio.

A reference standard to accurately define obesity in children. Scientists at the Children's Nutrition Research Center in Houston, Texas, continue to update the CNRC contemporary reference standards for body composition (fat, bone, muscle, water) for European-, African-, and Mexican-American children. These data provide standards for defining obesity in infants and children, and we have demonstrated that the most commonly used anthropometric index, the body mass index, does not adequately identify many of the overweight and obese children.  A more accurate identification of children with high risk for adult obesity is possible, such that appropriate diet/physical activity interventions can be efficiently targeted.

Health Promoting Properties of Plant and Animal Foods

Tea drinking reduces blood lipids.  It is widely believed that tea protects against cardiovascular disease due to beneficial antioxidant compounds, but there has been little evidence to support this concept.  Scientists at the BHNRC in Beltsville, MD, with collaborators at Unilever Research Laboratory, Vlaardingen, The Netherlands, found that drinking black tea lowered blood levels of total and low-density lipoprotein (LDL) cholesterol but did not improve biomarkers of oxidative stress.  Inclusion of black tea in a moderately low fat diet is protective against cardiovascular disease but the mechanism is the reduction of blood lipids rather than the lessening of oxidative stress.

High dietary calcium intakes from dairy products reduces body fat in adults.  WHNRC scientists, Davis CA, in collaboration with investigators from the University of Tennessee, Purdue University, and Ohio State University conducted a 12-week randomized, placebo controlled, multi-center weight loss trial examining the effect of a high calcium intake from dairy products or supplements on the loss of body weight and body fat in overweight and obese adults.  A high calcium diet did not significantly reduce body weight or alter body composition compared to a low calcium diet.  However, the high dairy diet increased weight loss and nearly doubled fat loss in comparison to the high supplemental calcium diet.  Thus, dairy-rich diets appear to augment weight loss by targeting the body fat compartment during energy restriction.

Phytochemicals from blueberries are taken up by the brain.  Scientists at the HNRCA in Boston, MA, in collaboration with investigators from the University of Barcelona and Simmons College (Boston) found the number of polyphenolic antioxidant compounds (anthocyanins) entering the brain in old rats fed a blueberry diet was positively correlated with their memory performance on a water maze task. These findings suggest that blueberry flavonoids may deliver their antioxidant and signaling modifying capabilities to the brain and affect behavior in rats. 

Soy protein has only minimal cholesterol-lowering effects.  Scientists at the HNRCA in Boston, MA, examined the effect of soy protein and soy-derived isoflavones on blood lipids in men and women over the age of 50 years.  Soy isoflavones had no significant effect on plasma lipid levels either constituent to the soy protein or supplemental to animal protein.  Although potentially helpful when used to displace products containing animal fat from the diet, the regular intake of relatively high levels of soy protein (>50 g/day) had only a modest effect on blood cholesterol levels and only in subjects with elevated LDL cholesterol levels.

Vitamin C enhances iron absorption in small children.  Preventing the causes of anemia in children is a growing national concern.  Researchers at the CNRC in Houston, TX carried out studies that confirmed the importance of Vitamin C containing juices to enhance iron absorption in children.

Bioavailability of Nutrients and Food Components

Type of carbohydrate consumed as part of a moderate-fat diet pattern alters lipid metabolism.  When dietary fat is consumed in moderate amounts, as recommended in the US Dietary Guidelines, carbohydrate provides the major source of dietary energy.  However, reducing fat consumption has not led to the anticipated reduction in chronic diseases like obesity, diabetes, and cardiovascular disease in the U.S.  Scientists at the WHNRC in Davis, CA, measured cardiovascular disease risk factors in overweight women consuming moderate fat diets containing carbohydrate-rich foods with a high glycemic index (refined grain products) or a low glycemic index (whole grain products).  Preliminary results show that meals containing low glycemic-index carbohydrates can reduce blood glucose, insulin and triglycerides as well as increase fat utilization for energy production.  The quality of carbohydrates consumed as part of a moderate-fat diet appears to alter lipid metabolism, and low glycemic-index carbohydrates result in a more favorable cardiovascular risk profile in women.

Glycerol and fatty acids optimize glucose synthesis in very low birth weight infants.  Infants in this at-risk group have high glucose requirements due to their brains accounting for a larger proportion of body weight than normal-weight infants.  Thus, new approaches to supplying sufficient glucose for these infants are needed.  Investigators at the Children’s Nutrition Research Center (CNRC) in Houston, TX, found that glycerol and fatty acids support glucose synthesis better than amino acids in the very low birth weight infants.  The information is important for designing optimum nutrition for this vulnerable group.

Total parenteral nutrition (TPN) likely diminishes intestinal function in neonates. 

Premature infants are lactase deficient and have been shown to poorly digest dietary lactose; premature infants also receive TPN, which suppresses intestinal growth and absorptive surface area.  Studies by scientists at the CNRC in Houston, TX, found that newborn piglets administered TPN for one week had diminished intestinal digestive and absorptive functions.  The findings suggest TPN administered to premature infants could impair their digestive capabilities.

Anthocyanins in fruits are absorbed intact based upon human studies.

Scientists at the ACNC in Little Rock, AR, have shown that anthocyanins, the components responsible for the dark colors of many fruits, are absorbed intact without metabolism.  This is different from other food flavonoid compounds that are metabolized prior to absorption. Scientists also identified several metabolites of anthocyanins that are apparently formed following absorption through methylation or conjugation processes.

Intestinal cell copper storage helps prevent copper toxicity.  Although excessive copper intake is toxic for humans, scientific data is currently inadequate to establish the upper safe limit for copper intake.  Scientists at the WHNRC in Davis, CA, supplemented young men consuming their usual diet with 7 mg/d of copper for 4.5 months (a high copper intake).  The copper content of intestinal cells increased significantly but did not enter systemic circulation.  This suggests a mechanism by which the human body adapts to a high dietary copper intake in order to prevent copper toxicity. 

Sequence of starch digestive enzyme glucoamylase.  Starch from grains and tubers contribute 60-80% of calories in the human diet, thus a greater understanding of starch digestion is needed. Scientists at the Children's Nutrition Research Center in Houston, TX, sequenced membrane-bound glucoamylase, the enzyme known to digest starch. A secreted glucoamylase, which binds to dietary starch granules in the small and large intestinal cavity, was discovered in the membrane-bound glucoamylase knockout mouse; the experiment revealed a redundancy in this digestive pathway that explains why the membrane-bound glucoamylase deficient mouse digested starch normally.