Jamie L Westcott

Iron absorption and iron status are reduced after Roux-en-Y gastric bypass

BACKGROUND Iron deficiency and iron deficiency anemia are common in patients who undergo gastric bypass. The magnitude of change in iron absorption is not well known. OBJECTIVE The objective was to evaluate the effects of Roux-en-Y gastric bypass (RYGBP) on iron status and iron absorption at different stages after surgery. We hypothesized that iron absorption would be markedly impaired immediately after surgery and would not improve after such a procedure. DESIGN Anthropometric, body-composition, dietary, hematologic, and iron-absorption measures were determined in 67 severe and morbidly obese women [mean age: 36.9 +/- 9.8 y; weight: 115.1 +/- 15.6 kg, body mass index (BMI: in kg/m(2)); 45.2 +/- 4.7] who underwent RYGBP. The Roux-en-Y loop length was 125-150 cm. Determinations were carried out before and 6, 12, and 18 mo after surgery. Fifty-one individuals completed all 4 evaluations. RESULTS The hemoglobin concentration decreased significantly throughout the study (repeated-measures analysis of variance). The percentage of anemic subjects changed from 1.5% at the beginning of the study to 38.8% at 18 mo. The proportion of patients with low serum ferritin increased from 7.5% to 37.3%. The prevalence of iron deficiency anemia was 23.9% at the end of the experimental period. Iron absorption from both a standard diet and from a standard dose of ferrous ascorbate decreased significantly after 6 mo of RYGBP to 32.7% and 40.3% of their initial values, respectively. No further significant modifications were noted. CONCLUSION Iron absorption is markedly reduced after RYGBP with no further modifications, at least until 18 mo after surgery.

Absorption of calcium from tortilla meals prepared from low-phytate maize

BACKGROUND Calcium fortification of maize has been achieved for millennia in Central America by the process of nixtamalization. Bioavailability of calcium is, however, compromised by phytate, which is present in large quantities in maize kernels and is only modestly reduced by nixtamalization. OBJECTIVE The objective was to compare the absorption of calcium from tortilla meals prepared from low-phytate maize with that from meals prepared from maize with typical phytate content. DESIGN At 1-mo intervals, 5 healthy adult women were fed 2 test meals of approximately 140 g tortillas in lieu of breakfast. On one occasion, the tortillas were prepared from maize with approximately 60% phytate reduction, and, on the other occasion, they were prepared from the matching isohybrid wild-type maize. Beginning midway through the test meal, (44)Ca (0.3 mg/kg body wt) was administered in water as an extrinsic label; (42)Ca (0.06 mg/kg body wt) was administered intravenously immediately after the test meal. Isotope ratios of (42)Ca to (43)Ca and of (44)Ca to (43)Ca were measured by inductively coupled plasma mass spectrometry in urine collected as an 8-h pool from the period 16-24 h after intravenous tracer administration and prepared by the oxalate precipitation method. Fractional absorption of calcium was determined by using a dual-isotope ratio technique. RESULTS Mean fractional absorption of calcium from tortillas prepared from the low-phytate maize (0.50 +/- 0.03) was significantly (P = 0.003) greater than that from tortillas prepared from the control maize (0.35 +/- 0.07). CONCLUSION The increase in the quantity of calcium absorbed could be of practical importance for calcium nutriture when the intake of dairy products is limited.

Zinc absorption and zinc status are reduced after Roux-en-Y gastric bypass: a randomized study using 2 supplements

BACKGROUND Micronutrient deficiencies are common in patients undergoing gastric bypass. The effect of this type of surgery on zinc absorption and zinc status is not well known. OBJECTIVE The objective was to evaluate the effects of Roux-en-Y gastric bypass (RYGBP) on zinc status and zinc absorption at different stages after surgery. We hypothesized that zinc status would be significantly impaired after surgery and that this impairment would be less severe in subjects receiving increased supplemental zinc. We also hypothesized that zinc absorption would be lower after surgery. DESIGN Anthropometric and body-composition variables and dietary and biochemical indexes of zinc status and zinc absorption were determined in 67 severe and morbidly obese women [mean (±SD) age: 36.9 ± 9.8 y; BMI (in kg/m(2)): 45.2 ± 4.7] who underwent RYGBP. The subjects were randomly assigned to 1 of 2 vitamin-mineral supplementation groups. Measurements were made before and 6, 12, and 18 mo after surgery. Fifty-six subjects completed the 18-mo follow-up. RESULTS Mean plasma zinc, erythrocyte membrane alkaline phosphatase activity, and the size of the rapidly exchangeable zinc pool decreased after RYGBP. Percentage zinc absorption decreased significantly from 32.3% to 13.6% at 6 mo after RYGBP and to 21% at 18 mo after surgery. No effect of supplement type was observed. CONCLUSIONS Zinc status is impaired after RYGBP, despite the finding that dietary plus supplemental zinc doubled recommended zinc intakes in healthy persons. Zinc absorption capacity is significantly reduced soon after RYGBP, with no major changes until 18 mo after surgery.

Relationships Among Plasma Zinc, Plasma Prolactin, Milk Transfer, and Milk Zinc in Lactating Women

The objective was to analyze interrelationships among plasma zinc (PZ), plasma prolactin (PRL), milk transfer, and milk zinc from a longitudinal study of lactating women with a range of zinc intakes. Sixteen of 26 women received a 15 mg/d zinc supplement, resulting in a significant increase in total zinc intake compared with nonsupplemented participants (P < .001). No significant differences in key variables were observed between the zinc-supplemented and non—zinc-supplemented women; data were thus combined. An inverse trend between PRL and PZ was observed at 0.5 (r = −.36, P = .08) and 7 months (r = −.38, P = .06). Correlations between PRL at 0.5 months and at 3, 5, and 7 months were significant (r > .50, P < .01). PRL concentrations and milk transfer were positively correlated at 5 (r = .67, P < .001) and 7 months (r = .53, P < .01), consistent with PRL role in lactation maintenance. Studies including zinc-deficient lactating women are required to clarify the interrelationships between zinc status and PRL secretion. J Hum Lact. 23(2): 179-183.

Bioavailability of zinc oxide added to corn tortilla is similar to that of zinc sulfate and is not affected by simultaneous addition of iron.

Background Corn tortilla is the staple food of Mexico and its fortification with zinc, iron, and other micronutrients is intended to reduce micronutrient deficiencies. However, no studies have been performed to determine the relative amount of zinc absorbed from the fortified product and whether zinc absorption is affected by the simultaneous addition of iron. Objective To compare zinc absorption from corn tortilla fortified with zinc oxide versus zinc sulfate and to determine the effect of simultaneous addition of two doses of iron on zinc bioavailability. Methods A randomized, double-blind, crossover design was carried out in two phases. In the first phase, 10 adult women received corn tortillas with either 20 mg/kg of zinc oxide added, 20 mg/kg of zinc sulfate added, or no zinc added. In the second phase, 10 adult women received corn tortilla with 20 mg/kg of zinc oxide added and either with no iron added or with iron added at one of two different levels. Zinc absorption was measured by the stable isotope method. Results The mean (± SEM) fractional zinc absorption from unfortified tortilla, tortilla fortified with zinc oxide, and tortilla fortified with zinc sulfate did not differ among treatments: 0.35 ± 0.07, 0.36 ± 0.05, and 0.37 ± 0.07, respectively. The three treatment groups with 0, 30, and 60 mg/kg of added iron had similar fractional zinc absorption (0.32 ± 0.04, 0.33 ± 0.02, and 0.32 ± 0.05, respectively) and similar amounts of zinc absorbed (4.8 ± 0.7, 4.5 ± 0.3, and 4.8 ± 0.7 mg/day, respectively). Conclusions Since zinc oxide is more stable and less expensive and was absorbed equally as well as zinc sulfate, we suggest its use for corn tortilla fortification. Simultaneous addition of zinc and iron to corn tortilla does not modify zinc bioavailability at iron doses of 30 and 60 mg/kg of corn flour.