Biomedical subjects

E R Monsen

Publications and source records attributed to E R Monsen.

At least 37 records · Page 2Linked to original sources

PubMed1988

Research methods in nutrition and dietetics: design, data analysis, and presentation.

Most problems in practice may be addressed through research. To show the applicability of research to all areas of nutrition and dietetics, seven types of research designs are discussed in this article: qualitative research; case series and surveys--both categorized as descriptive research; and experimental design, quasiexperimental design, cohort (follow-up) studies, and case-control studies--the four of which are categorized as analytical research because each design tests hypotheses of causal relationships. Sample size, subject selection, and statistical analysis and interpretation are discussed as appropriate to each research design. Numerous examples are presented, along with the basic research designs. Each section and subsection is numbered so that the article can serve easily as a reference and its component parts can be accessed readily. Research provides answers to questions and, generally, raises further questions that future research can address. Among the benefits of well-designed research are answers to clearly stated research questions, useful comparisons between options, information to guide evaluations of protocols, and data to document and support one's professional activities and one's staff.

Clinical Trials as Topic↗

PubMed1988

Iron nutrition and absorption: dietary factors which impact iron bioavailability.

Iron deficiency is widely observed worldwide, yet, paradoxically, iron is the most plentiful heavy metal in the earth's crust. Although absorption of iron from the gastrointestinal tract is strictly controlled, excretion is limited to iron lost from exfoliation of skin and gastrointestinal cells, customary and abnormal blood loss, and menses. Individuals highly vulnerable to iron deficiency have high iron needs, as during growth or pregnancy; high iron loss, as during marked hemorrhage or excessive and/or frequent menstrual losses; or diets with low iron content or bioavailability. Food iron is classified as heme or nonheme. Approximately half of the iron in meat, fish, and poultry is heme iron. Depending on an individual's iron stores, 15% to 35% of heme iron is absorbed. Food contains more nonheme iron and, thus, it makes the larger contribution to the body's iron pool despite its lower absorption rate of 2% to 20%. Absorption of nonheme iron is markedly influenced by the levels of iron stores and by concomitantly consumed dietary components. Enhancing factors, such as ascorbic acid and meat/fish/poultry, may increase nonheme iron bioavailability fourfold.

Ascorbic Acid↗

PubMed1985

Iron fortification of infant foods. A decade of change.

A survey of iron-fortified commercial foods commonly marketed for consumption by infants was conducted in 1972 and again in 1982. Positive changes had occurred in infant formulas and cereals during that decade, in availability of fortifying iron, level of fortification, and label information. Miscellaneous iron-containing products, cookies, and crackers were unreliable sources of dietary iron in both 1972 and 1982. Availability of fortifying iron in regular cereals had improved by 1982, though 10 percent lacked the label information. Fortified infant formulas and cereals contribute iron of high bioavailability to the typical infant diet in amounts equal to the USRDA. Food manufacturers need to continue to apply knowledge gained through research to sustain the lessened but still highly prevalent incidence of anemia in 1-2-year old children.

Biological Availability↗

PubMed1982

Iron status of elderly Americans.

Studies of iron nutriture in the elderly are limited and very few include observations on individuals over the age of 75. The two Health and Nutrition Examination Surveys carried out by the United States Department of Health, Education and Welfare demonstrate that the mean iron intake of Americans is adequate until the age of 75. However, with changes in the major food sources there is a decrease in iron derived from meat and a concomitant rise in the proportion supplied by breakfast cereals. Alterations in dietary iron bioavailability++ that may result from this have not been studied. Physiological data suggest that the elderly do not represent a target population for iron deficiency since iron requirements are no greater than those of adult men and lower than those of children and menstruating women. Furthermore, there is little direct evidence of a high prevalence of iron deficiency in the elderly, but the laboratory measurements that have proved useful in defining iron status in younger people have not been standardized for or extensively used in older people. Anemia is still the most important known consequence of significant iron deficiency. However, the application of Hb or hematocrit standards used in younger people to the elderly as well as the assumption that anemia can be equated with iron deficiency invalidates the conclusions of many surveys. Hb and hematocrit measurements are not suitable screening tests for iron deficiency in the elderly and there is an urgent need for a clearer understanding of the physiological and nutritional factors responsible for lower Hb values in older people, particularly older Blacks.

Adolescent↗

PubMed1982

Calculating dietary iron bioavailability: refinement and computerization.

Previous laboratory studies have shown that dietary iron during digestion forms two pools: heme and nonheme. Even though human beings absorb heme iron at a higher rate than nonheme iron, the major portion of food iron is nonheme (all grain and vegetable iron plus approximately 60 percent of the iron in meat, fish, and poultry). The absorption rate of nonheme iron can be increased markedly by concomitant consumption of ascorbic acid and/or meat/fish/poultry. These concepts have been incorporated into a model for estimating the quantity of bioavailable iron, the first trace mineral to be thus considered. This model has now been revised for easier and more refined application.

Ascorbic Acid↗

PubMed1979

Food iron absorption in human subjects. V. Effects of the major dietary constituents of semisynthetic meal.

Studies were performed in adult volunteer subjects to determine the effect on nonheme iron absorption of protein, carbohydrate, and fat. These constituents were administered as egg albumin, dextrimaltose, and corn oil, respectively, in a semisynthetic meal containing 700 kcal and 4.1 mg iron. Because any one of these ingredients are unpalatable when administered alone, their effect was determined by serially deleting or doubling their content in the basal semisynthetic meal. With both approaches, carbohydrate and fat had little influence whereas egg albumin had a significant inhibitory effect on the absorption of nonheme iron.

Absorption↗

PubMed1979

Priorities of nutritional concepts assigned by health professionals and students.

Medical faculty, practicing physicians, medical students, and dietitians/nutritionists rated nutritional concepts as to their importance for inclusion in the medical school curricula and indicated the best method of accomplishing this. Ten concepts were rated "essential." They related to biochemical and physiological aspects of nutrition; nutrition in pregnancy, lactation, growth, development, maturity, and old age; nutritional management in disease; drug and diet interrelationships; and critiques of popular dietary regimens. Ranked as "important" were eight concepts regarding sources of nutrition information; evaluation of nutritional status; recommended dietary allowances; and food additives, naturally occurring food toxins, and nutrient composition of foods. Based on results of this study, the authors make recommendations regarding nutritional concepts that should be included in medical school curricula and how these concepts should be incorporated.

Attitude of Health Personnel↗

PubMed1978

Estimation of available dietary iron.

Dietary iron requirements are dependent on the amount and availability of food iron ingested. On the basis of recent studies of food iron absorption employing extrinsic tag techniques, the availability of heme iron has been defined and estimates of the availability of nonheme iron based on the amounts of enhancing substances appear possible. A model has been developed whereby the availability of iron in a given meal may be estimated. Calculations are made on a meal basis of 1) the amount of heme iron and its availability, and 2) the amount of nonheme iron and its availability as influenced by the meal's content of enhancing factors. Examples of these calculations are provided.

Absorption↗

PubMed1977

Vitamin C, the common cold, and iron absorption.

A sizable segment of the population was found to be taking large quantities of vitamin C to reduce the number or severity of upper respiratory infections. To determine the affect of this supplementation on iron balance, multiple radioiron absorption tests were performed in 63 male subjects. The increase in iron absorption from a semisynthetic meal was directly proportional to the amount of ascorbic acid added over a range of 25 to 1,000 mg. The ratio of iron absorption with/without ascorbic acid at these two extremes was 1.65 and 9.57, respectively. The relative increase was substantially less when the test meal contained meat. A large dose of vitamin C taken with breakfast did not effect iron absorption from the noon or evening meal. A telephone survey of 100 individuals revealed that 67 were taking supplemental ascorbic acid in doses ranging as high as 2 g daily. The average intake of supplemental ascrobic acid in this population was 280 mg daily. If taken only with breakfast, this level of supplementation would produce a nearly 2-fold increase in the amount of iron absorbed daily. If taken in divided doses with each mean, the increase in iron absorption would be more than 3-fold.

Adolescent↗

PubMed1976

Food iron absorption in human subjects. IV. The effects of calcium and phosphate salts on the absorption of nonheme iron.

The influence of physiological levels of calcium and phosphorus on the absorption of nonheme iron from a semisynthetic meal was evaluated. Each of the 34 participating subjects received two to four test meals. In three studies where both calcium and phosphate were added, absorption of nonheme iron was reduced to 27 to 47% of that absorbed when no salts were added. However, with the single addition of either calcium or phosphate to the test meals no significantly inhibiting effect was observed. As the absorption of nonheme iron was significantly reduced only with the combined addition of calcium and phosphate, it is suggested that a calcium-phosphate-iron complex forms which inhibits iron absorption.

Absorption↗

PubMed1976

Food iron absorption in man II. The effect of EDTA on absorption of dietary non-heme iron.

One hundred and eighty iron absorption tests were performed in 45 normal men to determine the effect of EDTA on the absorption of dietary non-heme iron. The addition of 50 mg EDTA to test meals containing 4.1 mg iron reduced absorption by approximately one-half from meals of both high (standard meal) and low (semisynthetic meal) iron availability. Studies employing dual radioiron labels demonstrated complete isotopic exchange of ferric EDTA with dietary non-heme iron. Further studies were carried out to determine the decrease in food iron absorption at varying levels of EDTA. At a 1:1 molar ratio of EDTA to iron, absorption of non-heme iron was reduced to 72% and at a 2:1 molar ratio, to 50% of absorption without EDTA. These levels of EDTA are within the range believed to be present in the United States diet.

Adolescent↗

PubMed1976

Food iron absorption in human subjects. III. Comparison of the effect of animal proteins on nonheme iron absorption.

The ability of various animal proteins to enhance the absorption of dietary nonheme iron was evaluated by performing multiple radioiron absorption measurements in 70 volunteer subjects. Protein equivalent substitutions of nine animal foods were made in two basic test meals. The first was a standard meal of high iron availability (mean absorption, 8.3%) containing beef muscle as the animal protein. The second was a semisynthetic meal of low iron availability (mean absorption, 1.4%) containing ovalbumin as the protein source. Two categories of animal protein were defined. Substitution of beef, lamb, pork, liver, fish, and chicken for the egg ovalbumin in the sannisynthetic meal resulted in a significant, 2-fold to 4-fold increase in iron absorption whereas no increase was observed with milk, cheese, or egg. Reciprocal findings were obtained when these foods were substituted for the beef contained in the standard meal. All sources of animal proteins are not equivalent in their effect on nonheme iron absorption.

Absorption↗

PubMed1975

Food iron absorption. I. Use of semisynthetic diet to study absorption of nonheme iron.

Recent studies have established the validity of employing an extrinsic radioiron tag to measure the absorption of nonheme iron from a complex meal. In the present study, extrinsic tagging was used to measure absorption of nonheme iron from a standard meal chosen as representative of a typical American meal, and from a semisynthetic meal having the same total chemical composition. The latter was designed so that the major dietary components could be systematically altered to determine their separate effects on food iron absorption. Absorption from the standard meal in 32 healthy women averaged 10.0% as compared with a mean absorption of 1.8% from semisynthetic meal. Most but not all of this fivefold difference in absorption could be explained by the enhancing effect of meat in the standard meal. The low availability of iron from the semisynthetic meal will be of particular value in studying factors which enhance food iron absorption, whereas the standard meal is suitable for studying factors which reduce availability of food iron.

Absorption↗

PubMed1974