Legacy of Wilbur O. Atwater: human nutrition research expansion at the USDA--interagency development of food composition research.

The systematic chemical analysis of foods for human consumption in the United States had its origin with Wilbur O. Atwater. This activity began in the 1860s while Atwater was a student at Yale University and continued through his tenures at Wesleyan University and the Storrs (Connecticut) Experiment Station. These activities moved with Atwater to the USDA in Washington, DC and ultimately to the Henry D. Wallace Beltsville Agricultural Research Center in Beltsville, MD early in the 1900s. During the first half of the 20th century, food composition activities were guided by the discovery of new essential nutrients and the need to measure and tabulate their levels in foods. Later in the century, the association between diet and chronic diseases was recognized. As a result, collaborations were established between other food- and health-related government agencies, the food industry, and many universities. At the same time, computer and communication technology greatly advanced, which became integral to laboratory instrumentation and allowed data in the National Nutrient Databank System to be available electronically. Simultaneously, accuracy of analytical data came under scrutiny and a new paradigm was established in collaboration with governmental metrology units worldwide. Advances in computer technology and the increased focus on accuracy of analytical data subsequently led to the development of quality indicators for all food composition data. Recently, increased consumption of dietary supplements resulted in the broadening of food composition efforts and development of new collaborations with government agencies, several industries, and universities.

Concentrations of anthocyanins in common foods in the United States and estimation of normal consumption.

Anthocyanins (ACNs) are water-soluble plant pigments that have important functions in plant physiology as well as possible health effects. Over 100 common foods were screened for ACNs, and 24 of them were found to contain ACNs. Concentrations of total ACNs varied considerably from 0.7 to 1480 mg/100 g of fresh weight in gooseberry ('Careless' variety) and chokeberry, respectively. Not only does the concentration vary, but the specific anthocyanins present in foods are also quite different. Only six common aglycones, delphinidin, cyanidin, petunidin, pelargonidin, peonidin, and malvidin, were found in all of these foods. However, their sugar moieties and acylation patterns varied from food to food. Results from this study will add to the available data for the USDA Nutrient Database of flavonoids. On the basis of the concentration data and updated food intake data from NHANES 2001-2002, the daily intake of ACNs is estimated to be 12.5 mg/day/person in the United States. Of the different aglycones, cyanidin, delphinidin, and malvidin were estimated to contribute 45, 21, and 15%, respectively, of the total ACN intake. Nonacylated contributed 77% compared to 23% from acylated ACNs.

Flavonoid content of U.S. fruits, vegetables, and nuts.

Analytical data are reported for 20 flavonoids (as aglycones) determined for more than 60 fresh fruits, vegetables, and nuts collected from four regions across the United States at two times of the year. Sample collection was designed and implemented by the Nutrient Data Laboratory (USDA). Analyses of eight flavan-3-ols (catechin, catechin gallate, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, gallocatechin, and gallocatechin gallate), six anthocyanins (cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin), two flavanones (hesperetin and naringenin), two flavones (apigenin and luteolin), and two flavonols (myricetin and quercetin) were performed by the Food Composition Laboratory (USDA) using a hydrolysis method for the anthocyanidins, flavones, and flavonols and a direct extraction method for the flavan-3-ols and flavanones. Experimental results compare favorably (few statistically significant differences) to literature values in the flavonoid and proanthocyanidin database previously compiled by the Nutrient Data Laboratory. The results of this study showed a seasonal variation only for blueberries. This study also showed that the variation in the flavonoid content of foods, as purchased by the U.S. consumer, is very large. The relative standard deviation, averaged for each flavonoid in each food, was 168%.

A method for the analysis of natural and synthetic folate in foods.

The essentiality of dietary folates for human beings has been known for many years. Over the shorter term, biological activities associated with several human maladies and the attenuation of biomarkers for several chronic diseases also have been assigned to folates. In the United States, these observations have led to the addition of folic acid to several foods and food ingredients (food fortification) and to dietary recommendations that assign biological activity to each of the forms of folate in the food supply. There currently is unavailable a robust, instrumental procedure that will distinguish between naturally occurring food folates and synthetic folic acid as part of the routine analysis of foods. The procedure proposed in this publication is unique in that it uses "off-the-shelf" supplies and instrumentation, to the extent possible, and was developed with "normal" corporate work schedules in mind. This method takes advantage of the tri-enzyme food digestion and folate deconjugation steps but was optimized with a commercially available rat plasma as the source of conjugase. A high-capacity styrene-divinylbenzene-based solid-phase extraction column was identified, and conditions were developed for quantitative recovery of 5-methyltetrahydrofolate and folic acid (FA) with it. The various forms of food folates are separated on a C-18 high-performance liquid chromatography (HPLC) column which is resistant to degradation at low pH. As a result, the mobile phase was simplified to a gradient of low-pH phosphate buffer (pH 2.2) and acetonitrile. Although FA does not exhibit fluorescence, a UV-induced photolysis system was added, which is controlled by the HPLC system, so that an appropriate segment of the HPLC column effluent is subjected to photolytic conditions and, thereby, FA can be measured as a fluorescent product. The application of the system was verified by analyzing several certified reference materials and foods and comparing results with certified values and/or total folate values as determined by microbiological assay.

Lipophilic and hydrophilic antioxidant capacities of common foods in the United States.

Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORAC(FL)) assay with fluorescein as the fluorescent probe and 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin-Ciocalteu reagent. Hydrophilic ORAC(FL) values (H-ORAC(FL)) ranged from 0.87 to 2641 micromol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORAC(FL) values (L-ORAC(FL)) ranged from 0.07 to 1611 micromol of TE/g. Generally, L-ORAC(FL) values were <10% of the H-ORAC(FL) values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORAC(FL) and H-ORAC(FL). Differences of ORAC(FL) values in fruits and vegetables from different seasons and regions were relatively large for some foods but could not be analyzed in detail because of the sampling scheme. Two different processing methods, cooking and peeling, were used on selected foods to evaluate the impact of processing on ORAC(FL). The data demonstrated that processing can have significant effects on ORAC(FL). Considering all of the foods analyzed, the relationship between TP and H-ORAC(FL) showed a very weak correlation. Total hydrophilic and lipophilic antioxidant capacity intakes were calculated to be 5558 and 166 micromol of TE/day, respectively, on the basis of data from the USDA Continuing Survey of Food Intakes by Individuals (1994-1996).

Overview of dietary flavonoids: nomenclature, occurrence and intake.

Flavonoids and their polymers constitute a large class of food constituents, many of which alter metabolic processes and have a positive impact on health. Flavonoids are a subclass of polyphenols. They generally consist of two aromatic rings, each containing at least one hydroxyl, which are connected through a three-carbon "bridge" and become part of a six-member heterocyclic ring. The flavonoids are further divided into subclasses based on the connection of an aromatic ring to the heterocyclic ring, as well as the oxidation state and functional groups of the heterocyclic ring. Within each subclass, individual compounds are characterized by specific hydroxylation and conjugation patterns. Many flavonoids in foods also occur as large molecules (tannins). These include condensed tannins (proanthocyanidins), derived tannins and hydrolysable tannins. For proanthocyanidins, three subclasses (15 characterized) have been identified in foods. Monomers are connected through specific carbon-carbon and ether linkages to form polymers. Derived tannins are formed during food handling and processing, and found primarily in black and oolong teas. Flavonoids are widely distributed in nature, albeit not uniformly. As a result, specific groups of foods are often rich sources of one or more subclasses of these polyphenols. The polyphenolic structure of flavonoids and tannins renders them quite sensitive to oxidative enzymes and cooking conditions. Scientists in several countries have estimated intakes of a few subclasses of flavonoids from limited food composition databases. These observations suggest large differences in consumption, due in part to cultural and food preferences among populations of each country.

Nutrient content of five commonly consumed Jamaican foods

There is a dearth of food composition data for the foods and dishes most frequently consumed in Jamaica. Samples of five foods in their forms most commonly consumed by the Jamaican population (brown stewed chicken, rice and peas, boiled and roasted breadfruit, and steamed callaloo) were collected and analysed for proximates, dietary fiber, and minerals. Also determined were the cholesterol level of brown stewed chicken and the carotenoid content of steamed callaloo. National samples of mixed dishes were collected from 10 representative households while samples of single foods were purchased from 10 Jamaican markets and roadside vendors nationwide. Primary samples of each food were pooled to form composites from which analytical samples were drawn. Analytical results of brown stewed chicken and rice and peas revealed substantive amounts of protein, total fat, and several of the minerals. Steamed callaloo and boiled and roasted breadfruit were most noted for their potential contribution to dietary fiber and the minerals calcium, potassium, magnesium, and phosphorus. This is the first report on nutrient composition data for commonly consumed Jamaican foods.

Nutrient content of five commonly consumed Jamaican foods

There is a dearth of food composition data for the foods and dishes most frequently consumed in Jamaica. Samples of five foods in their forms most commonly consumed by the Jamaican population (brown stewed chicken, rice and peas, boiled and roasted breadfruit, and steamed callaloo) were collected and analysed for proximates, dietary fiber, and minerals. Also determined were the cholesterol level of brown stewed chicken and the carotenoid content of steamed callaloo. National samples of mixed dishes were collected from 10 representative households while samples of single foods were purchased from 10 Jamaican markets and roadside vendors nationwide. Primary samples of each food were pooled to form composites from which analytical samples were drawn. Analytical results of brown stewed chicken and rice and peas revealed substantive amounts of protein, total fat, and several of the minerals. Steamed callaloo and boiled and roasted breadfruit were most noted for their potential contribution to dietary fiber and the minerals calcium, potassium, magnesium, and phosphorus. This is the first report on nutrient composition data for commonly consumed Jamaican foods.(Au)