Phyllis E. Johnson

Dietary calcium and manganese effects on menstrual cycle symptoms.

OBJECTIVE This exploratory study was designed to determine whether dietary calcium and manganese affect menstrual symptoms in healthy women. STUDY DESIGN Ten women with normal menstrual cycles completed the Menstrual Distress Questionnaire each cycle during a 169-day, live-in metabolic study of calcium and manganese nutrition. Women were assigned in a double-blind, Latin-square manner to each of four 39-day dietary periods: 587 or 1336 mg calcium per day with 1.0 or 5.6 mg manganese per day. Responses were analyzed by repeated-measures analysis of variance. RESULTS Increasing calcium intake reduced mood, concentration, and behavior symptoms generally (p < or = 0.05), reduced pain during the menstrual phase of the cycle (p = 0.034), and reduced water retention during the premenstrual phase (p = 0.041). In spite of increasing calcium intake, lower dietary manganese increased mood and pain symptoms during the premenstrual phase (p < or = 0.05). CONCLUSION Dietary calcium and manganese may have a functional role in the manifestation of symptomatology typically associated with menstrual distress.

Effect of copper intake on balance, absorption, and status indices of copper in men

Indices of Cu status were measured in 8 men fed diets low in Cu (0.89±0.10 mg/day), for periods ranging from 105 to 120 days. One man showed Cu depletion signs of significantly decreased plasma Cu, 8.7 μmole/L, at the end of depletion, vs 12.1 μmole/L during equilibration and 11.0 μmole/L at the end of repletion, and decreased RBS superoxide dismutase (SOD), 705 U/g Hgb at the end of depletion vs 3619 U/g Hgb at the end of repletion. Two others exhibited similar trends. Copper absorption by the men was not affected by the amount of dietary Cu. However, endogenous excretion of Cu during depletion was 50% of that during the control period (1.00±0.20 vs 0.50±0.17 mg Cu/d, p<0.0002) for control and depletion periods, respectively. Intakes of below 0.9 mg/d apparently result in signs of Cu depletion in healthy adults. Sex differences need to be considered when determining the effect of Cu depletion on various indices of Cu status.

In vitro hepatic thyroid hormone deiodination in iron-deficient rats: Effect of dietary fat

The effects of different dietary fats on thyroid indices were studied in weanling iron-deficient rats. Rats were fed one of five different diets (safflower oil with a casein protein source, safflower oil with defatted beef as the protein source, prime rib, beef tallow with casein and stearate with casein). Both dietary fat and iron status (adequate, CN; deficient, ID; or iron-deficient replete, ID-replete) had significant effects on body weight and hemoglobin concentrations. The tallow-fed animals weighed the least relative to animals fed the other fats; ID rats were smaller than CN rats. The tallow- and stearate-fed animals had the highest hemoglobin concentrations. Type of dietary fat affected plasma thyroxine (T4), but not plasma triiodothyronine (T3) or rate of deiodination of reverse T3 (rT3). Iron deficiency decreased plasma concentrations of T3 and T4 and increased in vitro hepatic rT3 deiodination, suggesting that the ID animals tend to metabolize thyroid hormones via deactivating pathways. The alterations in thyroid hormone metabolism associated with iron deficiency are reversible with iron repletion.

Availability of iron to rats from spirulina, a blue-green alga

Abstract Both cultured Spirulina platensis (Nordst.) Geitl,a blue-green alga, and commercially available dried Spirulina contained high levels of iron, 300–400 ppm on a dry weight basis. Iron availability to rats from cultured S. platensis and from commercial Spirulina equaled that of FeSO 4 . Ingestion of the daily dose of Spirulina (10 g) recommended for human consumption by the commercial source would provide up to 1.5–2 mg absorbed iron. However, both cultured and commercial Spirulina contained approximately 9.5 ppm Hg, so that chronic use may lead to mercury intakes above prudent levels.

Effect of bile/pancreatic secretions on absorption of radioactive or stable zinc : in vivo and in vitro studies

Biliary/pancreatic (B/P) secretions are a major component of endogenous secretions, and endogenously secreted Zn is a primary means of Zn homeostasis. This study examined whether B/P fluid alters the absorption/reabsorption of Zn and, in doing so, whether this contributes to homeostatic control of Zn. Animal experiments utilized rats fed 10 or 300 μg Zn/kg diet. An open-ended gut perfusion study in which65Zn-labeled B/P fluid or67Zn-labeled and digested diet found significantly decreased Zn absorption from B/P fluid. Although Zn absorption from both sources was less in animals fed diets higher in Zn, there was no interaction of treatment and diet. Further studies utilizing cultured human colon carcinoma cells (CACO-2) as in vitro models of gut enterocytes found that the presence of B/P fluid significantly decreased Zn retention and/or transport and resulted in a redistribution of cellular Zn after 1200 min of incubation. These studies show that a substance in B/P fluid can decrease the absorption of Zn and also suggest that dietary Zn and Zn associated with B/P secretions are absorbed from distinct pools. However, the lack of an interactive effect with diet, and the amount of time required to see differences in CACO-2 cells, suggest that differences in absorption are not a major contributor to Zn homeostasis.

Effect of Food Processing and Preparation on Mineral Utilization

While effects of various nutrients and certain non-nutrient components of food on mineral utilization have been intensively studied, less is known about the effects of food processing and preparation procedures. Fermentation during the production of beer, wine, yogurt, and African tribal foods affects bioavailability of Zn and Fe. Baking affects the chemical form of Fe in fortified bread products and these changes can affect its bioavailability. Availability of Fe in milk-based infant formula depends on whether Fe is added before or after heat processing. Food packaging (e.g., tin cans) can alter food composition and thus potentially affects mineral bioavailability. Maillard browning has been reported to cause slight decreases in Zn availability both in vitro and in humans. However, we found that feeding of highly browned casein-glucose products to rats as 5% of diet produced no effect on Zn absorption (59.5 +/- 8.2% vs 54.1 +/- 7.3%) or Fe absorption (45.6 +/- 7.7% vs 46.9 +/- 12.6%) for browned vs control, respectively; nor did we find any of the adverse health effects reported by others. We found no effect on stable Zn or Cu absorption in seven men when browned foods were fed, compared to the same diets without browning. Zinc absorption was 34 +/- 13% (browned) vs 24 +/- 15% (unbrowned), and Cu absorption was 55 +/- 5% vs 55 +/- 8% (p greater than 0.05).

What can in vitro methods tell us about mineral availability

In vitro studies of mineral bioavailability are useful because they are faster and less expensive than in vivo studies and because they offer better control over experimental variables. Selection of conditions for in vitro assays of mineral availability is arbitrary. Conditions vary widely among laboratories and with the mineral of interest. Absorption takes place in vivo under conditions that allow ongoing influx and efflux of nutrients and digestive secretions. Conditions in the digestive tract respond to the bulk and nutrient composition of a meal. How does one reproduce these conditions in a closed in vitro system? Correlations between in vivo and in vitro assays may depend on choice of conditions for in vivo studies. Studies of mineral bioavailability from soils have developed to the point that mathematical models have been developed that predict the bioavailability of various minerals to plants under field conditions. Definition of such a model for mineral bioavailability to animals or humans will probably be more difficult to achieve. More information is needed on the nature of nonmineral components of foods and how they interact with minerals.

Determination, stable isotope enrichment and kinetics of direct-reacting copper in blood plasma

Abstract Direct-reacting Cu is defined as Cu2+ and other forms of Cu that readily exchange with Cu2+ in blood plasma. An analytical method was developed for 1) quantification of direct-reacting Cu by stable isotope dilution and 2) determination of 65Cu enrichment of direct-reacting Cu in plasma samples from in vivo tracer studies. The method involved addition of enriched 65Cu to plasma, extraction with sodium diethyldithiocarbamate in mineral oil, and analysis by inductively coupled plasma mass spectrometry. Optimum sodium diethyldithiocarbamate concentration for the extraction was 0.16 mM. Direct-reacting Cu (means ± SD) varied from 3.4 ± 0.5% of whole plasma Cu in dairy cows (n = 7) and 3.4 ± 0.3% in healthy men (n = 10) to 16.6 ± 3.7% in dogs (n = 3). After intravenous infusion of enriched 65Cu into two healthy men, biological half-lives of 8.7 and 12.3 min were determined for direct-reacting Cu.

Bioavailability of Copper to Rats from Various Foodstuffs and in the Presence of Different Carbohydrates

Abstract Copper bioavailability was studied in rats using an extrinsic 67Cu label. Copper absorption from sunflower seeds (46%), peanuts (41%), cooked shrimp (50%), and cooked beef (40%) was as good or better than copper sulfate (46%). Copper from plant foods (sunflower seeds, garbanzo beans, peanuts) was absorbed equally as well as copper from animal foods (beef, shrimp, chicken liver), 39 ± 7% vs 43 ± 7%, P > 0.05. There was no significant difference in percentage Cu absorption between intrinsically labeled chicken liver and extrinsically labeled chicken liver. In a second experiment, Cu absorption was measured in the presence of glucose, fructose, sucrose, or cornstarch. There were no significant differences in Cu absorption due to different carbohydrates in a single meal.

Absorption of zinc and iron by rats fed meals containing sorghum food products

Zinc and iron absorption from freeze-dried, traditionally prepared sorghum food products was studied in rats. Following a period of marginal zinc or iron depletion, groups of rats (n = 6 in each group) were fed nutrient-balanced test meals containing one of four sorghum food products (fermented aceda ; acidic to, cooked with tamarind extract; neutral to, cooked in water; alkaline to, cooked with wood ash), cooked maize gruel or an egg-white control diet, each of which was extrinsically labeled with either 65Zn or 59Fe before being added to the diets. Absorption was determined by whole-body retention of the initial radioisotope dose over a period of 19 days. Iron was highly available from all products tested (75–83%) with no significant difference in absorption between groups. Zinc from fermented aceda (97%) was more available than that from the other sorghum products (69–78%) or maize gruel (76%) (P