Journal of Nutrition Nutrient Requirements and Optimal Nutrition

A High Mixed Protein Diet Reduces Body Fat without Altering the Mechanical Properties of Bone in Female Rats [Nutrient Requirements and Optimal Nutrition]

Tue, 20 Oct 2009 10:01:51 PDT

Long-term consumption of high-protein (HP) diets at 35% of energy is postulated to negatively influence bone health. Previous studies have not comprehensively examined the biochemical, physical, and biomechanical properties of bone required to arrive at this conclusion. Our objective in this study was to examine the long-term effect of a HP diet on bone metabolism, mass, and strength in rats. Adult female Sprague-Dawley rats (n = 80) were randomized to receive for 4, 8, 12, or 17 mo a normal-protein (NP) control diet (15% of energy) or a HP diet (35% of energy). Diets were balanced for calcium because the protein sources were rich in calcium. At each time point, measurements included weight, body composition, and bone mass using dual-energy X-ray absorptiometry, mechanical strength at the mid-diaphysis of femur and tibia, microarchitecture of femurs using microcomputerized tomography and serum osteocalcin, carboxy-terminal crosslinks of type I collagen (CTX), insulin-like growth factor-1 (IGF-1), leptin, and adiponectin. Effects of diet, time, and their interaction were tested using factorial ANOVA. The HP diet resulted in lower body weight, total body, and abdominal fat and higher lean mass. Serum leptin and adiponectin were greater in HP-fed than in NP-fed rats, but IGF-1 did not differ between the groups. Whereas the HP diet resulted in higher relative bone mineral content (g/kg) in the femur, tibia, and vertebrae, serum osteocalcin and CTX and bone internal architecture and biomechanical strength were unaffected. In conclusion, HP diets at 35% of energy lower body fat content without hindering the mechanical and weight-bearing properties of bone.

Linear and Ponderal Growth Trajectories in Well-Nourished, Iron-Sufficient Infants Are Unimpaired by Iron Supplementation [Nutrient Requirements and Optimal Nutrition]

Gahagan, S., Yu, S., Kaciroti, N., Castillo, M., Lozoff, B. — Tue, 20 Oct 2009 10:01:51 PDT

Iron deficiency remains the most common nutritional deficiency worldwide and supplementation is recommended during periods of high risk, including infancy. However, questions have been raised about possible adverse effects of iron on growth in iron-sufficient (IS) infants and the advisability of across-the-board iron supplementation. This study examined whether short- or long-term growth was impaired in IS infants who received iron supplementation. From a longitudinal study of healthy, breast-fed, low- to middle-income Chilean infants randomly assigned to iron supplementation or usual nutrition at 6 or 12 mo, we retrospectively identified infants meeting criteria for iron sufficiency at the time of random assignment (n = 273). Using multilevel analysis, ponderal and linear growth were modeled before, during, and after iron supplementation up to 10 y in 3 comparisons: 1) iron supplementation compared with usual nutrition from 6 to 12 mo; 2) iron supplementation compared with usual nutrition from 12 to 18 mo; and 3) 15 mg/d of iron as drops compared with iron-fortified formula (12 mg/L). Growth trajectories did not differ during or after supplementation indicating no adverse effect of iron in any comparison. These results suggest that, at least in some environments, iron does not impair growth in IS infants.

The Quantity of Zinc Absorbed from Wheat in Adult Women Is Enhanced by Biofortification [Nutrient Requirements and Optimal Nutrition]

Fri, 18 Sep 2009 10:01:30 PDT

Biofortification of crops that provide major food staples to large, poor rural populations offers an appealing strategy for diminishing public health problems attributable to micronutrient deficiencies. The objective of this first-stage human study was to determine the increase in quantity of zinc (Zn) absorbed achieved by biofortifying wheat with Zn. Secondary objectives included evaluating the magnitude of the measured increases in Zn absorption as a function of dietary Zn and phytate. The biofortified and control wheats were extracted at high (95%) and moderate (80%) levels and Zn and phytate concentrations measured. Adult women with habitual diets high in phytate consumed 300 g of 95 or 80% extracted wheat as tortillas for 2 consecutive days using either biofortified (41 mg Zn/g) or control (24 mg Zn/g) wheat. All meals for the 2-d experiment were extrinsically labeled with Zn stable isotopes and fractional absorption of Zn determined by a dual isotope tracer ratio technique. Zn intake from the biofortified wheat diet was 5.7 mg/d (72%) higher at 95% extraction (P < 0.001) and 2.7 mg/d (68%) higher at 80% extraction compared with the corresponding control wheat (P = 0.007). Zn absorption from biofortified wheat meals was (mean ± SD) 2.1 ± 0.7 and 2.0 ± 0.4 mg/d for 95 and 80% extraction, respectively, both of which were 0.5 mg/d higher than for the corresponding control wheat (P < 0.05). Results were consistent with those predicted by a trivariate model of Zn absorption as a function of dietary Zn and phytate. Potentially valuable increases in Zn absorption can be achieved from biofortification of wheat with Zn.

Prolonged Intake of Coenzyme Q10 Impairs Cognitive Functions in Mice [Nutrient Requirements and Optimal Nutrition]

Sumien, N., Heinrich, K. R., Shetty, R. A., Sohal, R. S., Forster, M. J. — Fri, 18 Sep 2009 10:01:30 PDT

Coenzyme Q₁₀ (CoQ₁₀) is widely consumed as a dietary supplement to enhance bioenergetic capacity and to ameliorate the debilitative effects of the aging process or certain pathological conditions. Our main purpose in this study was to determine whether CoQ₁₀ intake does indeed attenuate the age-associated losses in motor, sensory, and cognitive functions or decrease the rate of mortality in mice. Mice were fed a control nonpurified diet or that diet containing 0.68 mg/g (low dosage) or 2.6 mg/g (high dosage) CoQ₁₀, starting at 4 mo of age, and were tested for sensory, motor, and cognitive function at 7, 15, and 25 mo of age. Amounts of the ubiquinols CoQ₉H₂ and CoQ₁₀H₂ measured in a parallel study were augmented in the cerebral cortex but not in any other region of the brain. Intake of the low-CoQ₁₀ diet did not affect age-associated decrements in muscle strength, balance, coordinated running, or learning/memory, whereas intake at the higher amount increased spontaneous activity, worsened the age-related losses in acuity to auditory and shock stimuli, and impaired the spatial learning/memory of old mice. The CoQ₁₀ diets did not affect survivorship of mice through 25 mo of age. Our results suggest that prolonged intake of CoQ₁₀ in low amounts has no discernable impact on cognitive and motor functions whereas intake at higher amounts exacerbates cognitive and sensory impairments encountered in old mice. These findings do not support the notion that CoQ₁₀ is a fitness-enhancing or an "antiaging" substance under normal physiological conditions.

To Meet Nutrient Recommendations, Most French Adults Need to Expand Their Habitual Food Repertoire [Nutrient Requirements and Optimal Nutrition]

Thu, 20 Aug 2009 10:02:30 PDT

Simultaneous dietary achievement of a comprehensive set of nutrient recommendations is difficult. Our objective was to assess the feasibility of achieving a set of 30 nutrient recommendations at the individual level and characterize factors associated with feasibility. Seven-day food records collected from adults participating in the French national food consumption survey (n = 1171) were modified using an individualized diet optimization approach. For each individual, departure from his/her recorded diet was minimized, using only foods reported in his/her weekly diet record to fulfill a set of nutritional constraints. These constraints aimed to achieve or exceed the French Estimated Average Requirements and varied depending on the individual's gender, age, and observed nutrient intake levels. Acceptability constraints ensured realistic food portion sizes and food patterns. Model feasibility (i.e. percentage of feasible optimized diets) was calculated for all diets and by tertiles of dietary variety (i.e. the number of foods in the weekly food repertoire). Among the 1171 modeled diets, only 22% were mathematically feasible, showing that 78% of French adults would need to expand their weekly food repertoire to fulfill nutrient recommendations. Model feasibility increased from 6.6 to 50.3% and from 2.7 to 42.9% in tertiles 1 and 3 of dietary variety for men and women, respectively. The vitamin D constraint was the most difficult to fulfill (feasibility doubled after its removal), followed by sodium (maximum), magnesium (minimum), and SFA (maximum). The new approach developed in this study provides a method for identifying nutrient levels to carefully evaluate when establishing recommendations.