Benefits and safety of dietary protein for bone health-an expert consensus paper endorsed by the European Society for Clinical and Economical Aspects of Osteopororosis, Osteoarthritis, and Musculoskeletal Diseases and by the International Osteoporosis Foundation.

A summary of systematic reviews and meta-analyses addressing the benefits and risks of dietary protein intakes for bone health in adults suggests that dietary protein levels even above the current RDA may be beneficial in reducing bone loss and hip fracture risk, provided calcium intakes are adequate. Several systematic reviews and meta-analyses have addressed the benefits and risks of dietary protein intakes for bone health in adults. This narrative review of the literature summarizes and synthesizes recent systematic reviews and meta-analyses and highlights key messages. Adequate supplies of dietary protein are required for optimal bone growth and maintenance of healthy bone. Variation in protein intakes within the "normal" range accounts for 2-4% of BMD variance in adults. In older people with osteoporosis, higher protein intake (≥ 0.8-g/kg body weight/day, i.e., above the current RDA) is associated with higher BMD, a slower rate of bone loss, and reduced risk of hip fracture, provided that dietary calcium intakes are adequate. Intervention with dietary protein supplements attenuate age-related BMD decrease and reduce bone turnover marker levels, together with an increase in IGF-I and a decrease in PTH. There is no evidence that diet-derived acid load is deleterious for bone health. Thus, insufficient dietary protein intakes may be a more severe problem than protein excess in the elderly. Long-term, well-controlled randomized trials are required to further assess the influence of dietary protein intakes on fracture risk.

Diet diversity, growth and adiposity in healthy breastfed infants fed homemade complementary foods.

BACKGROUND/OBJECTIVES: Infant complementary feeding is important for establishing food preferences. Few studies exist on the effects of infant complementary feeding choices (food preparation methods) on dietary intake, growth or adiposity. We examined whether provision of homemade complementary food is associated with the development of dietary diversity, nutrient intakes and quality of infant growth. SUBJECTS/METHODS: Secondary analysis of feeding practices from a randomized trial of vitamin D supplementation in 132 healthy breastfed 1-month-old infants from Montréal, Canada. This longitudinal study used diet records, anthropometric and body composition data (dual-energy X-ray absorptiometry) from assessments that occurred when infants were 6, 9, 12 and 36 months of age. Infants were grouped into three categories of food preparation method on the basis of whether or not they had consumed homemade or commercial meat or fruit and vegetable by 9 months (homemade, commercial and both). Multivariable regression controlled for family income, maternal education and infant sex. RESULTS: Dietary data were available for 65 infants. By 9 months, 22% of infants had exclusively received homemade (n=14), 14 infants had exclusively received commercial and 37 infants had received both. The development of dietary diversity (number of World Health Organization-recommended food groups) was higher (0.76 (95% confidence interval (CI): 0.14, 1.38); P<0.05) in the homemade group versus commercial. Energy and nutrient intakes did not differ by group over time. The homemade group had 773 g (-1364, -182; P<0.01) lower whole-body fat mass and 7.1% (-12.6, -1.6; P<0.05) lower % body fat at 12 months compared with the reference group (both homemade and commercial). Reduced whole-body fat mass in the homemade group persisted at 36 months (-696 g (95% CI: -1341, -52); P<0.05). There were no differences between groups for changes in growth Z-scores (length-for-age, weight-for-age and body mass index-for-age). CONCLUSIONS: Provision of homemade complementary food is associated with increased dietary diversity during the first year of life and reduced adiposity.

Vitamin D supplementation trial in infancy: body composition effects at 3 years of age in a prospective follow-up study from Montréal.

BACKGROUND: The impact of vitamin D status on body composition is not well understood. OBJECTIVES: Evaluate how vitamin D supplementation in infancy affects body composition at 3 years of age. METHODS: Double-blind randomized trial of 132, 1-month-old healthy, breastfed infants randomly assigned to receive oral vitamin D3 supplements of 400, 800, 1200 or 1600 IU d-1 for 11 months. In the present analysis, 87 (66%) returned at 3 years of age. Body composition was measured using dual-energy x-ray absorptiometry and plasma 25-hydroxyvitamin D [25(OH)D] concentrations by liquid chromatography tandem mass spectrometry. RESULTS: Anthropometry, body composition, diet, activity and demographics were similar across dosage groups at 3 years. Mean 25(OH)D concentration from 1 month to 3 years was higher (P < 0.001) in the 1200 IU group than 800 and 400 IU groups. Children with 25(OH)D concentrations above 75 nmol L-1 had lower fat mass (~450 g; P = 0.049). In multiple linear regression, mean 25(OH)D was associated with lean mass percent (ß = 0.06; CI: 0.00, 0.12; P = 0.042), fat mass (ß = -11.29; CI: -22.06, -0.52; P = 0.048) and body fat percent (ß = -0.06; CI: -0.12, -0.01; P = 0.045). CONCLUSIONS: Higher vitamin D status from infancy through to 3 years of age associates with leaner body composition.

Vitamin D supplementation in breastfed infants from Montréal, Canada: 25-hydroxyvitamin D and bone health effects from a follow-up study at 3 years of age.

UNLABELLED: Whether infant vitamin D supplementation may have long-term bone benefits is unclear. In this study, breastfed infants who received vitamin dosages greater than 400 IU/day did not have higher bone mineralization at 3 years. This study provides important data to inform pediatric public health recommendations for vitamin D. INTRODUCTION: North American health agencies recommend breastfed infants should be supplemented with 400 IU of vitamin D/day to support bone health. Few studies examined the long-term benefits of early life vitamin D supplementation on bone mineralization. The objective of this study was to determine if a dose-response relationship exists between infant vitamin D supplementation, vitamin D status, and bone outcomes at 3 years of age. METHODS: This was a double-blind randomized trial of 132, 1-month-old healthy, breastfed infants from Montréal, Canada, between 2007 and 2010. In this longitudinal analysis, 87 infants (66 %) returned for follow-up at 3 years of age, between 2010 and 2013. At 1 month of age, participants were randomly assigned to receive oral cholecalciferol (vitamin D3) supplements of 400, 800, 1200, or 1600 IU/day until 12 months of age. Lumbar spine vertebrae 1-4 (LS) bone mineral density (BMD), LS and whole body bone mineral content (BMC), and mineral accretion were measured by dual-energy x-ray absorptiometry at 3 years. RESULTS: At follow-up, the treatment groups were similar in terms of diet, sun exposure, and demographics. There were no significant differences among the groups in LS or whole body BMC, BMD, or accretion. Although, 25(OH)D concentrations were not different among the groups, higher doses (1200 and 1600 IU/day) achieved higher 25(OH)D area under the curve from 1 to 36 months vs. 400 IU/day. CONCLUSIONS: This is the first longitudinal follow-up of an infant vitamin D dose-response study which examines bone mineralization at 3 years of age. Dosages higher than 400 IU/day do not appear to provide additional benefits to the bone at follow-up. Larger studies with more ethnically diverse groups are needed to confirm these results.

Toxicological assessment of kretek cigarettes Part 5: mechanistic investigations, inhalation toxicity.

The biological effects of mainstream smoke (MS) from Indonesian-blended cigarettes with and without added cloves, cloves extracted with hot ethanol, and extracted cloves replenished with eugenol or clove oil were assessed in a 90-day inhalation study in rats. A separate 35-day inhalation study in rats was performed with MS from American-blended cigarettes with 0%, 2.5%, 5% or 10% added eugenol. Effects commonly seen in inhalation studies with MS were observed. These included histopathological changes indicative of irritation in the entire respiratory tract and inflammatory responses in the lung. Adding cloves to American- or Indonesian-blended cigarettes reduced the inflammatory response in the lung but with no difference between the two blend types. When the clove oil was extracted (∼ 75% reduction of eugenol achieved) from cloves, the inflammatory response in the lung was still reduced similarly to whole cloves but the severity of histopathological changes in the upper respiratory tract was less reduced. Add back of clove oil or pure eugenol reduced this response to a level similar to what was seen with whole cloves. When eugenol was added to American-blended cigarettes, similar findings of reduced lung inflammation and severity of histopathological changes in respiratory the tract was confirmed. These studies demonstrate a clear effect of cloves, and in particular eugenol, in explaining these findings.

Dietary supplementation with long chain polyunsaturated fatty acids in pregnant guinea pigs has sex-dependent effects on growth and bone outcomes in offspring.

Long chain PUFA enhance bone mass in non-pregnant mammals. We examined the effects of arachidonic (AA; 20:4n-6) and docosahexaenoic (DHA; 22:6n-3) acid on bone mass of mothers and neonates. Guinea pig sows (n=15) were fed control, DHA or AA+DHA diets from mating to weaning. Measurements included: osteocalcin (OC), deoxypyridinoline (DPD), areal bone mineral density (aBMD) in sows and neonates; and volumetric density (vBMD) in neonates. Only vertebral aBMD and OC:DPD ratio declined during reproduction and only DHA reduced OC:DPD. Male pup weight was reduced by DHA and female weight elevated by AA+DHA. Whole body and femur aBMD were reduced by DHA and AA+DHA; whereas tibia vBMD was reduced by DHA in males. Female whole body, tibia and vertebrae aBMD plus tibia vBMD were elevated by AA+DHA; and DHA elevated whole body, tibia and vertebrae aBMD. Dietary AA+DHA and DHA elicit sex-dependent effects on neonatal bone, with minimal impact on mothers.

Long-chain polyunsaturated fatty acids: selected mechanisms of action on bone.

Evidence presented over the past 20 years has shown that long-chain polyunsaturated fatty acids (LCPUFAs), especially the n-3 fatty acids such as eicospentaenoic acid (EPA) and docosahexaenoic acid (DHA) are beneficial for bone health. Some studies in humans indicate that LCPUFAs can increase bone formation, affect peak bone mass in adolescents and reduce bone loss as measured using bone mineral densitometry. The cellular mechanisms of action of the LCPUFAs, however, are complex and involve modulation of fatty acid metabolites such as prostaglandins, resolvins and protectins, several signalling pathways, cytokines and growth factors. LCPUFAs affect receptor activator of nuclear factor κß (RANK), a receptor found on the osteoclast, the cell causing bone resorption, which controls osteoclast formation. Lipoxygenase (LOX) generated lipid mediators (resolvins, lipoxins, protectins and docosanoids) have both anti-inflammatory and pro-resolving activities. Both resolvins and lipoxins inhibit inflammation-induced bone resorption. Arachidonic acid significantly upregulates inducible NO synthase (iNOS) mRNA expression in human osteoblast-like cells, thereby possibly enhancing osteoclastic activity. The protective effect of EPA on osteoblastogenesis could be mediated by the biphasic cross-talk between PGE(2) and NO production involving COX-2 and iNOS pathways. Other mediators of osteoblast maturation include PPARα ligands such as linoleic acid and possibly DHA in association with bone morphogenic proteins. Since DHA is a weaker ligand for PPARγ, more uncommitted mesenchymal stem cells are thought to differentiate into osteoblasts rather than adipocytes. This review addresses selected cellular mechanisms that may explain the beneficial effects of the LCPUFAs on bone.

Feeding flaxseed oil but not secoisolariciresinol diglucoside results in higher bone mass in healthy rats and rats with kidney disease.

Flaxseed's oil and lignan, secoisolariciresinol diglucoside (SDG), are implicated in attainment of health and treatment of renal injury and osteoporosis. To test for these benefits, weanling Han:SPRD-cy rats (n=171) with or without kidney disease were randomized to diets made with either corn oil or flaxseed oil and with or without SDG for 12 weeks. In females, weight was lower with the SDG diet. In males fed flaxseed oil, lean mass was higher and fat % was lower. In both sexes, fat % was lower in diseased rats. Bone mineral content (BMC) and density were higher in rats fed flaxseed oil and lower in diseased rats, additionally; BMC was lower in SDG-supplemented females. The benefit of flaxseed oil on body composition is sex specific but the effect on bone mass is not. Lastly, reduced weight due to early rat kidney disease is not due to loss of lean body mass.

Effects of dietary supplementation with flax during prepuberty on fatty acid profile, mammogenesis, and bone resorption in gilts.

The possible role of dietary flax on pre-pubertal development of mammary glands and bone resorption was investigated in gilts. Fifty-seven gilts were fed 1 of 4 diets from 88 d of age until slaughter (d 212 +/- 1). Diets were control without flax (n = 14); 10% flaxseed supplementation (n = 13); 6.5% flaxseed meal supplementation (n = 15); and 3.5% flaxseed oil supplementation (n = 15). All diets were isonitrogenous and isocaloric. Jugular blood samples were obtained on d 78 and 210 to establish the fatty acid profile and to determine the concentrations of prolactin, estradiol, and cross-linked N-telopeptides of type I collagen. At slaughter, the mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and the composition of the parenchymal tissue (protein, fat, DM, and DNA) was determined. Histochemical analyses of the mammary parenchyma were performed, and fatty acid profiles in the extraparenchymal tissue were evaluated. Dietary flax increased (P < or = 0.001) the concentrations of PUFA and decreased those of SFA (P < 0.01) and MUFA (P < or = 0.001) in plasma and extraparenchymal tissues, which was largely due to the inclusion of 10% flaxseed or 3.5% flaxseed oil (P < or = 0.01) but not 6.5% flaxseed meal. Circulating concentrations of prolactin and estradiol were unaltered by treatments (P > 0.1), but concentrations of cross-linked N-telopeptides of type I collagen tended to be greater (P < 0.1) in flax-supplemented gilts. The DM content of parenchymal tissue was the only mammary compositional value affected, showing an increase with flax addition (P < 0.05). No change (P > or = 0.1) in the bromodeoxyuridine labeling index or estrogen receptor localization was observed with treatments. Dietary supplementation with flax as seed, meal, or oil, therefore, brought about the expected changes in the fatty acid profile but had no beneficial effects on mammary development or bone resorption.

The effect of prostaglandin E(2) (PGE(2)) and long-chain polyunsaturated fatty acids (LC PUFA) on bone formation in piglets: a model for bone growth in nutritional investigation.

This research investigates the effects of exogenous prostaglandin E(2) (PGE(2)) treatment and arachidonic acid supplementation on the rate of growth in modelling bone of piglets. The piglet is a good model for the study of infant nutrition and bone growth. PGE(2) and long-chain polyunsaturated fatty acid (LC PUFA) supplementation, alone and in combination, are shown to have little or no effect on cortical bone thickness. Though exogenous PGE(2) supplementation and LC PUFA supplementation may both be effective in promoting bone growth and mass in adults, they do not appear to have the same positive effect on bone growth in infancy over a short term. A dynamic model for bone growth in piglets is proposed here for the first time. This research adds to our knowledge of the relationship between the dynamic histology of bone, the rate of osteogenesis, and the link between nutrition and bone growth.

The effect of prostaglandin E2 and arachidonic acid on dentinogenesis in pigs.

The rate of dentinogenesis for the pig is quantified and the effects of dietary arachidonic acid supplementation and/or exogenous prostaglandin on dentine formation are defined. Thirty-six pigs were randomised to four groups, receiving either standard or supplemented formula and either prostaglandin E2 or placebo injections for fifteen days. Double tetracycline banding is used to measure rate of growth in the teeth. The average rate of dentinogenesis for all the study animals is 17.96 microm/day. Results show that the rate of dentinogenesis is not significantly affected by the interaction of hormone and dietary supplementation.

Dietary supplementation of arachidonic acid is associated with higher whole body weight and bone mineral density in growing pigs.

Essential fatty acids are fundamental to normal growth and development, but North American formulas do not contain arachidonic (AA) and docosahexaenoic acid (DHA). The main objective of the present study was to determine whether addition of AA and DHA to formula elevates growth and bone mineralization in piglets. A secondary objective was to establish whether liver fatty acid composition is related to that of bone. Twelve 10-d-old male piglets were randomized to receive either a standard formula with an n-6:n-3 fatty acid ratio of 4.9:1.0 or the same formula made with an equal amount of fat but containing AA (0.5% wt/wt total fat) and DHA (0.1% wt/wt total fat) for 14 d. Piglets in the supplemented group had significantly (p < 0.05) higher weight and greater bone mineral density of the whole body, lumbar spine, and femur. No differences were observed in whole body length, calcium absorption, or biochemical markers of bone metabolism. Feeding AA resulted in lower linoleic acid (p < 0.05) and higher (p < 0.05) AA in liver total lipid (% wt/wt) and bone FFA (% wt/wt) but no change to DHA. Liver AA (% wt/wt total lipid) was positively related (p < 0.05) to growth, free AA (% wt/wt) in bone, bone mineral content, bone mineral density, and urinary prostaglandin E2 but negatively related (p < 0.05) to free linoleic acid in bone. Inverse relationships were observed when liver linoleic acid was substituted for liver AA as the independent variable. These data indicate that feeding AA is associated with elevated weight and higher whole body and regional bone mineral density.

Longitudinal assessment of growth and bone mineral accretion in prematurely born infants treated for chronic lung disease with dexamethasone.

The objective of this study in premature infants was to assess the relationship between dexamethasone, growth and bone mineral accretion. Nine appropriate size for gestational age premature infants treated for chronic lung disease with tapering doses of dexamethasone (0.5-0.1 mg/kg/day over 37 +/- 7 days) were individually matched to a comparison infant by sex, gestational age, birth-weight, and type of feed. Infant growth and bone mineral accretion were measured at equivalent gestational ages from recruitment until 6 months corrected age. During hospitalization, mean rate of weight, length and head circumference growth and bone mineral accretion in the distal radius were significantly lower in the dexamethasone-treated infants in spite of similar nutrient intakes. Dexamethasone infants had significantly lower plasma phosphorus, and urinary calcium, pyridinoline and N-telopeptide excretion. Dexamethasone affected absolute length, but not weight, throughout the study. No significant differences were observed in body composition or absolute radial and whole body bone mineral content. The results indicate that dexamethasone therapy compromises growth and bone mineral accretion in small premature infants. 'Catch-up' linear growth was not evident at 6 months of age and reflects the importance of early nutrition interventions.

Effects of selenium deficiency on testicular morphology and function in rats.

For four generations rats were fed a low selenium diet (2-7 micrograms Se kg-1) or the same diet with 250 or 300 micrograms Se kg-1 added as selenite. In male rats of the first generation that had been fed the diets from the age of 20 days onwards, selenium depletion led to slightly delayed testis growth during pubertal development that was compensated for in the later stages of maturation. In adult rats fed the low selenium diet for nearly a year no changes in testicular mass and morphology were observed. The serum concentration of testosterone of 6-month-old, selenium-depleted animals was, however, slightly lower than that of adequately supplied controls, and the stimulation of testosterone secretion by administration of GnRH or LH resulted in a significantly less marked rise in the serum concentration of testosterone. From the second generation onwards the testis mass, expressed as a percentage of the body mass, decreased and in the fourth generation was less than 50% of that of the controls. The male gonads of fourth generation animals showed a severe bilateral atrophy, in which the seminiferous tubules were considerably reduced in diameter and almost entirely lined by Sertoli cells and a few stem cells. Differentiated spermatozoa could not be detected. The alterations were reversible and spermatogenesis was restored by feeding the selenium-adequate diet. The findings indicate that testicular morphology and functions are affected by severe selenium deficiency and that the element is necessary for testosterone biosynthesis and the formation and normal development of spermatozoa.