Donald Oberleas

Mechanism of zinc homeostasis.

Homeostatic equilibrium of a nutrient is characteristic of a healthy body. For zinc, phytate has been shown to alter that equilibrium in several monogastric species including man. The pancreas is an important organ in the maintenance of zinc homeostasis. Elevated calcium has been shown to be a synergistic agent in affecting the rate of onset and rate of homeostatic change. In the studies described, rats were depleted of zinc to differing extents, zinc was injected intraperitoneally to label the endogenous zinc pool. Phytate- and nonphytate-containing protein diets were fed and feces were collected. Feces were counted for radioactivity. The ratios of radioactivity (phytate:nonphytate) indicated that the major effect of phytate was on the endogenous secreted pool. Evidence is included to indicate that two, pancreatic labile pools of zinc are secreted, one is stable complexes not affected by phytate and two, a labile pool of zinc readily available for complexation. A mathematical model is included that fits all nutritional models for zinc homeostasis.

The rate of chromium transit through the gastrointestinal tract

Abstract The rate of movement of chromium (III) chloride through the gastrointestinal tract of rats was investigated. In the first experiment 85% of rats intubated with 51 CrCl 3 had more than 1% of the administered 51 Cr below the cecum after four hours. In the second study, most 51 Cr recovered in the small intestine reached the ileum one hour after initiation of feeding 2 g diet containing 51 CrCl 3 . In the third experiment, the intestine was ligated in situ; ligation blocked 51 Cr transit. 51 Chromium appeared to be associated with the fluid portion of the ingesta which may negate the use of CrCl 3 as a marker for rate of passage of dietary components.

Treatment of zinc deficiency without zinc fortification

Zinc (Zn) deficiency in animals became of interest until the 1950s. In this paper, progresses in researches on physiology of Zn deficiency in animals, phytate effect on bioavailability of Zn, and role of phytase in healing Zn deficiency of animals were reviewed. Several studies demonstrated that Zn is recycled via the pancreas; the problem of Zn deficiency was controlled by Zn homeostasis. The endogenous secretion of Zn is considered as an important factor influencing Zn deficiency, and the critical molar ratio is 10. Phytate (inositol hexaphosphate) constituted up to 90% of the organically bound phosphorus in seeds. Great improvement has been made in recent years on isolating and measuring phytate, and its structure is clear. Phytate is considered to reduce Zn bioavailability in animal. Phytase is the enzyme that hydrolyzes phytate and is present in yeast, rye bran, wheat bran, barley, triticale, and many bacteria and fungi. Zinc nutrition and bioavailability can be enhanced by addition of phytase to animal feeds. Therefore, using phytase as supplements, the most prevalent Zn deficiency in animals may be effectively corrected without the mining and smelting of several tons of zinc daily needed to correct this deficiency by fortification worldwide.

The Influence of Iron and Zinc Supplementation on the Bioavailability of Provitamin A Carotenoids from Papaya Following Consumption of a Vitamin A-Deficient Diet

Iron deficiency anemia, zinc and vitamin A deficiencies are serious public health problems in Cameroon, as in many developing countries. Local vegetables which are sources of provitamin A carotenoids (PACs) can be used to improve vitamin A intakes. However, traditional meals are often unable to cover zinc and iron needs. The aim of this study was to determine the bioavailability of 3 PACs (α-carotene, β-carotene, and β-cryptoxanthin) in young men, who were fed with a vitamin A-free diet and received iron and zinc supplementation. Twelve healthy participants were divided into three groups and were supplemented with elemental iron (20 mg of iron fumarate), 20 mg of zinc sulfate or iron+zinc (20 mg of iron in the morning and 20 mg of zinc in the evening) for 11 d. They were given a vitamin A- and PAC-free diet from the 6th to the 11th day, followed by a test meal containing 0.55 kg of freshly peeled papaya as a source of PACs. Blood samples were collected four times successively on the 11th day (the test meal day), at T0 (just after the test meal), after 2 h (T2), after 4 h (T4) and after 7 h (T7). Ultracentrifugation was used to isolate serum chylomicrons. Retinol appearance and PAC postprandial concentrations were determined. The supplementation with zinc, iron and iron+zinc influenced the chylomicron appearance of retinol and PACs differently as reflected by retention times and maximum absorption peaks. Iron led to highest retinol levels in the chylomicron. Zinc and iron+zinc supplements were best for optimal intact appearance of α-carotene, β-carotene and β-cryptoxanthin respectively. Supplementation with iron led to the greatest bioavailability of PACs from papaya and its conversion to retinol.

Trace elements in foods of children from Cameroon: A focus on zinc and phytate content

In developing countries, complementary foods are based on local cereal porridges. These foods are poor in trace elements, with a high risk of inducing micronutrient deficiencies-the primary cause of mortality in children under the age of five. Inappropriate feeding of complementary foods is the major factor creating malnutrition and micronutrients deficiencies in Cameroon children, as well as in other developing countries. This study determined the zinc and phytate content of 30 complementary foods that were based on maize or Irish potatoes. The foods were blended or treated by dehusking, fermentation and germination. Zinc was measured by flame atomic absorption spectrophotometry and phytates by high pressure-liquid chromatography; then phytates/zinc molar ratios were calculated. Concentrations (mg/100g dry matter) ranged, respectively, from 0.20 to 2.58 (0.12 ± 0.67) for zinc and from 0.00 to 6.04 (1.87 ± 1.7) for phytates. The phytate/zinc ratio varied from 0.00 to 51.62 (11.12 ± 11.53). It appears that germination and fermentation reduced the level of phytates: however, zinc levels in the samples did not change significantly. The traditional, local complementary foods were not only poor in zinc, but contained very high levels of phytates. These phytates have the potential to considerately reduce the acid extraction of zinc, and could impair its bioavailability.