Maintaining a constant state of cellular zinc nutrition, or homeostasis, is essential for normal function. In animals and humans, adjustments in zinc absorption and endogenous intestinal excretion are the primary means of maintaining zinc homeostasis. The adjustments in gastrointestinal zinc absorption and endogenous excretion are synergistic. Shifts in endogenous excretion appear to occur quickly with changes in intake just above or below optimal intake. The absorption of zinc responds more slowly, but it has the capacity to cope with large fluctuations in intake. With extremely low zinc intakes or with prolonged marginal intakes, secondary homeostatic adjustments may augment the gastrointestinal changes. These secondary adjustments include changes in urinary zinc excretion, a shift in plasma zinc turnover rates and, possibly, an avid retention of zinc released from selected tissues, such as bone, in other tissues to maintain function.

ObjectiveTo determine whether adding mindfulness‐based eating and stress management practices to a diet‐exercise program improves weight loss and metabolic syndrome components.MethodsIn this study 194 adults with obesity were randomized to a 5.5‐month program with or without mindfulness training and identical diet‐exercise guidelines. Intention‐to‐treat analyses with multiple imputation were used for missing data. The primary outcome was 18‐month weight change.ResultsEstimated effects comparing the mindfulness to control arm favored the mindfulness arm in (a) weight loss at 12 months, −1.9 kg (95% CI: −4.5, 0.8; P = 0.17), and 18 months, −1.7 kg (95% CI: −4.7, 1.2; P = 0.24), though not statistically significant; (b) changes in fasting glucose at 12 months, −3.1 mg/dl (95% CI: −6.3, 0.1; P = 0.06), and 18 months, −4.1 mg/dl (95% CI: −7.3, −0.9; P = 0.01); and (c) changes in triglyceride/HDL ratio at 12 months, −0.57 (95% CI: −0.95, −0.18; P = 0.004), and 18 months, −0.36 (95% CI: −0.74, 0.03; P = 0.07). Estimates for other metabolic risk factors were not statistically significant, including waist circumference, blood pressure, and C‐reactive protein.ConclusionsMindfulness enhancements to a diet‐exercise program did not show substantial weight loss benefit but may promote long‐term improvement in some aspects of metabolic health in obesity that requires further study.

Cutaneous cholecalciferol synthesis has not been considered in making recommendations for vitamin D intake. Our objective was to model the effects of sun exposure, vitamin D intake, and skin reflectance (pigmentation) on serum 25-hydroxyvitamin D (25[OH]D) in young adults with a wide range of skin reflectance and sun exposure. Four cohorts of participants (n = 72 total) were studied for 7-8 wk in the fall, winter, spring, and summer in Davis, CA [38.5 degrees N, 121.7 degrees W, Elev. 49 ft (15 m)]. Skin reflectance was measured using a spectrophotometer, vitamin D intake using food records, and sun exposure using polysulfone dosimeter badges. A multiple regression model (R(2) = 0.55; P < 0.0001) was developed and used to predict the serum 25(OH)D concentration for participants with low [median for African ancestry (AA)] and high [median for European ancestry (EA)] skin reflectance and with low [20th percentile, approximately 20 min/d, approximately 18% body surface area (BSA) exposed] and high (80th percentile, approximately 90 min/d, approximately 35% BSA exposed) sun exposure, assuming an intake of 200 iu/d (5 ug/d). Predicted serum 25(OH)D concentrations for AA individuals with low and high sun exposure in the winter were 24 and 42 nmol/L and in the summer were 40 and 60 nmol/L. Corresponding values for EA individuals were 35 and 60 nmol/L in the winter and in the summer were 58 and 85 nmol/L. To achieve 25(OH)D > or =75 nmol/L, we estimate that EA individuals with high sun exposure need 1300 iu/d vitamin D intake in the winter and AA individuals with low sun exposure need 2100-3100 iu/d year-round.

Zinc is essential for normal fetal growth and development and for milk production during lactation. The metabolic adjustments made in zinc utilization to meet these needs have not been described. The purpose of this study was to determine whether fractional zinc absorption (FZA) is altered during pregnancy and lactation and, if so, to determine whether the change is related to maternal zinc status, specifically, concentrations of zinc in plasma, erythrocytes, urine, and breast milk and dietary zinc intake. Thirteen women were studied at five time points: once preconception; at 8-10, 24-26, and 34-36 wk gestation; and once while they were lactating 7-9 wk postpartum. Zinc intake increased by 35 mumol/d (2.3 mg/d) from preconception to 34-36 wk (P = 0.04); it tended to decrease (P > 0.05) during lactation but did not return to the preconception level. The amount of zinc in breast milk averaged 2.0 mg/d at the lactation time point. FZA measured from urinary enrichments of two stable isotopes of zinc increased from 14% preconception to 25% during lactation (P = 0.023) but the increase to 19% at 34-36 wk gestation was not significant. No increase in FZA occurred in four women who took iron supplements during lactation. FZA was negatively correlated with plasma zinc concentration at 34-36 wk gestation and with urinary zinc excretion at all time points. The nearly twofold increase in zinc absorption during lactation was presumably in response to the demand for zinc to synthesize breast milk.

A mathematical model of zinc metabolism in six healthy women (average age: 30 +/- 11 y) was developed by using stable isotopes of zinc. After equilibration on a constant diet containing 7.0 mg Zn/d, an oral tracer highly enriched in 67Zn and an intravenous tracer highly enriched in 70Zn were administered simultaneously. Multiple plasma and 24-h urine samples were collected for the next 7 d with complete fecal collections for 11 d. Tracer-trace ratios in plasma, urine, and feces were calculated from isotope ratios of 67Zn to 66Zn and 70Zn to 66Zn measured by using inductively coupled plasma-mass spectrometry. An a priori identifiable model composed of seven compartments was developed to describe the kinetics of both tracers as well as that of naturally occurring zinc. The parameters of the model were fitted to the data by using the SAAM-CONSAM modeling software and were estimated with good precision. Several important, not directly measurable zinc variables were estimated (mean +/- SEM) from the model including the fractional absorption from the gastrointestinal tract (0.279 +/- 0.043), the rates of endogenous secretion (2.79 +/- 0.49 mg/d) and excretion (2.01 +/- 0.35 mg/d), the fractional turnover rate of the plasma pool (131 +/- 20/d), and the sizes (7.2 +/- 1.2 and 77.1 +/- 6.4 mg) and fractional turnover rates (22.3 +/- 7.1 and 1.49 +/- 0.18/d) of the fast and slow tissue pools equilibrating with the plasma, respectively.

Obesity is a strong risk factor for the development of CVD, hypertension and type 2 diabetes. The overall goal of the present pilot study was to feed strawberries, in the form of freeze-dried powder, to obese subjects to determine whether dietary strawberries beneficially altered lipid profiles and reduced blood markers of inflammation compared with a control intervention. A total of twenty healthy subjects (thirteen females and seven males) aged between 20 and 50 years with a BMI between 30 and 40 kg/m 2 completed the present 7-week double-blind, randomised, cross-over trial. Each subject received a prepared diet 7 d/week for 7 weeks consisting of approximately 35 % of energy from fat, 20 % protein, 45 % carbohydrate and 14 g fibre. Blood was collected on days 1 and 8 for baseline information. After the first week, subjects were randomly assigned to the strawberry powder (equivalent to four servings of frozen strawberries) or control (strawberry-flavoured) intervention for 3 weeks. For the remaining 3 weeks, subjects crossed over to the opposite intervention. Blood was collected again at the end of weeks 3, 4, 6 and 7. A comprehensive chemistry panel, lipid profile analyses and measurement of inflammatory mediators were performed for each blood draw. A 3-week dietary intervention with strawberry powder reduced plasma concentrations of cholesterol and small HDL-cholesterol particles, and increased LDL particle size in obese subjects (P, 0·05). Dietary strawberry powder reduced risk factors for CVD, stroke and diabetes in obese volunteers, suggesting a potential role for strawberries as a dietary means to decrease obesity-related disease.

Biofortification of cassava with the provitamin A carotenoid b-carotene is a potential mechanism for alleviating vitamin A deficiency. Cassava is a staple food in the African diet, but data regarding the human bioavailability of b-carotene from this food are scarce. The objective of the present study was to evaluate provitamin A-enhanced cassava as a source of b-carotene and vitamin A for healthy adult women. The study was a randomised, cross-over trial of ten American women. The subjects consumed three different porridges separated by 2 week washout periods. Treatment meals (containing 100 g cassava) included: biofortified cassava (2 mg b-carotene) porridge with added oil (15 ml peanut or rapeseed oil, 20 g total fat); biofortified cassava porridge without added oil (6 g total fat); unfortified white cassava porridge with a 0·3 mg retinyl palmitate reference dose and added oil (20 g total fat). Blood was collected six times from 2 0·5 to 9·5 h post-feeding. TAG-rich lipoprotein (TRL) plasma was separated by ultracentrifugation and analysed using HPLC with coulometric array electrochemical detection. The AUC for retinyl palmitate increased after the biofortified cassava meals were fed (P, 0·05). Vitamin A conversion was 4·2 (SD 3·1) and 4·5 (SD 3·1) mg b-carotene:1 mg retinol, with and without added oil, respectively. These results show that biofortified cassava increases b-carotene and retinyl palmitate TRL plasma concentrations in healthy well-nourished adult women, suggesting that it is a viable intervention food for preventing vitamin A deficiency.

The kinetic analysis with a compartmental model suggests that the profound decrease in plasma zinc concentrations after 5 wk of severe zinc depletion was mainly due to a decrease in the rate of zinc release from the most slowly turning over body zinc pool.