Effects of exercise frequency and training volume on bone changes following a multi-component exercise intervention in middle aged and older men: Secondary analysis of an 18-month randomized controlled trial.

Progressive resistance training (PRT) combined with weight-bearing impact exercise are recommended to optimize bone health, but the optimal frequency and dose of training remains uncertain. This study, which is a secondary analysis of an 18-month intervention in men aged 50-79 years, examined the association between exercise frequency and the volume of training with changes in DXA and QCT-derived femoral neck (FN) and lumbar spine (LS) bone outcomes, respectively. Men were allocated to either thrice-weekly PRT plus impact exercise training (n = 87) or a non-exercising (n = 85) group. Average weekly exercise frequency (ExFreq) and training volume per session [PRT volume (weight lifted, kg), number of weight-bearing impacts (jumps completed) and total training volume] over the 18-months were calculated from the participants' exercise cards. Regression analysis showed that average weekly ExFreq and training volume per session were positively associated with the 18-month changes in FN BMD and LS trabecular volumetric BMD. Men completing on average 1 to <2 and ≥2 sessions/week had a 1.6 to 2.2% greater net gain in FN BMD relative to non-exercising men, while those completing ≥2 sessions/week had 3.9 to 5.2% net gain in LS trabecular vBMD compared to non-exercising men and those completing <1 session/week. Further analysis showed that the average number of impact loads per session, but not the average PRT weight-lifted, was positively associated with changes in BMD. Every 10 impact loads per session over 18 months was associated with a 0.3% and 1.3% increase in FN BMD and LS trabecular vBMD, respectively. In conclusion, this study indicates that exercise frequency and training volume were predictors of the changes in hip and spine BMD following a multi-component exercise program, and that the number of impact loads rather than PRT weight lifted per session was more important for eliciting positive skeletal responses in middle-aged and older men.

Effects of a multi-modal resistance exercise program and calcium-vitamin D3 fortified milk on blood pressure and blood lipids in middle-aged and older men: secondary analysis of an 18-month factorial design randomised controlled trial.

PURPOSE: Physical activity and dietary interventions are recommended as front-line therapy for prevention and management of cardiovascular disease. This study investigated the independent and combined effects of low-fat, calcium-vitamin D3 fortified milk and multi-modal exercise training on blood pressure (BP) and blood lipids in middle-aged and older men. METHODS: This was a pre-planned secondary analysis of an 18-month, randomised controlled trial. Community-dwelling men aged 50-79 years (n = 180) were randomised into (i) exercise + fortified milk; (ii) fortified milk; (iii) exercise; or (iv) control. The low-fat milk (400 mL/day) was fortified with 1,000 mg/day calcium and 800 IU/day of vitamin-D3, whilst the exercise intervention consisted of three sessions/week of resistance- and weight-bearing impact exercises. Resting BP and fasting lipids were assessed at baseline, 6 (lipids only), 12 and 18 months. RESULTS: Mean ± SD serum 25(OH)D and calcium intake for the entire cohort at baseline was 86 ± 36 nmol/L and 1002 ± 397 mg/day, respectively, with 10% classified as vitamin-D insufficient and 58% reporting a calcium intake below 1000 mg/day. There were no exercise-by-fortified milk interactions, nor any main-group effects for exercise or milk on BP or lipids at any time. However, there were significant reductions from baseline to 18 months in systolic (mean change, 5-8 mmHg) and diastolic (4-6 mmHg) BP in the exercise, fortified milk and control groups. All results remained largely unchanged after adjusting for use of anti-hypertensive or lipid lowering medication, weight or fat mass, or only including men with hypertension (n = 89) or dyslipidemia (n = 130) at baseline. CONCLUSION: Supplementation with low-fat, calcium + vitamin D3 fortified milk and a multi-modal exercise program, alone or in combination, was not effective for improving BP or blood lipids in community-dwelling middle-aged and older men.

Effects of a multicomponent exercise program combined with calcium-vitamin D3-enriched milk on health-related quality of life and depressive symptoms in older men: secondary analysis of a randomized controlled trial.

PURPOSE: Osteoporosis is associated with both lower health-related quality of life and depression in older people. We examined the independent and combined effects of a multi-component exercise program and calcium-vitamin D3 fortified milk on health-related quality of life (HR-QoL) and depression in older men. METHODS: In this 12-month, factorial design randomized controlled trial, 180 healthy community-dwelling men aged 50-79 years with normal to below average bone mineral density were allocated into one of four groups: exercise + fortified milk; exercise; fortified milk; or controls. Exercise consisted of high-intensity resistance training with weight-bearing exercise (3 days per week; 60-75 min per session). Men assigned to fortified milk consumed 400 ml/day of low-fat milk containing 1000 mg/day calcium and 800IU/day vitamin D3. Questionnaires were used to assess HR-QoL (SF-36) and depressive symptoms (Center for Epidemiologic Studies Depression Scale) at baseline, and 6 and 12 months. A linear mixed model analysis was used to test whether there was a synergistic interaction between exercise and calcium-vitamin D3. If no significant interactions were detected, the main effects of exercise and fortified milk were examined. RESULTS: Mean adherence to the exercise program and fortified milk was 67% (95% CI 61, 73%) and 90% (95% CI 86, 93%), respectively. There were no exercise-by-fortified milk interactions nor main effects of exercise or calcium-vitamin D for any of the HR-QoL measures or depressive symptoms. CONCLUSION: In healthy community-dwelling older men, exercise training and/or calcium-vitamin D fortified milk did not improve HR-QoL or depressive symptoms.

In vivo endogenous proteolysis yielding beta-casein derived bioactive beta-casomorphin peptides in human breast milk for infant nutrition.

Objective Beta-casein is a major protein in breast milk and an important source for several bioactive peptides that are encrypted within the sequence. Beta-casomorphins (BCMs) are short-chain proteolytic peptides that are derived from the beta-casein protein and have opioid effects in newborns. Human milk is known to contain naturally occurring milk-protein-derived bioactive peptides but the identification of naturally occurring beta-casein-derived BCMs in human breast milk has been limited due to difficulties in the detection of BCM peptides, which are small and circulate in low concentrations. Methods The present study aimed to identify the naturally occurring BCM peptides from beta-casein in human breast milk using liquid chromatography-tandem mass spectrometry. The BCM peptides identified in the breast milk were analysed to predict the milk proteases responsible for the cleavage patterns using a computational tool EnzymePredictor. Results In-depth peptidomics analysis of breast milk samples that were collected at different lactation stages during human lactation revealed the presence of BCMs including BCM-8, -9, -10, and -11 as well as precursors and truncated forms of the original peptide, which suggests that milk protease activity in the mammary gland generates biologically relevant BCMs. Conclusions To our knowledge, this is the first report to describe the presence of naturally occurring human BCM-10 and -11 in breast milk. Our study provides evidence of beta-casein-derived BCM peptides in human milk before infant digestion. Proteases that are present in milk are likely specific in their proteolysis of beta-casein. The identified bioactive BCM-8, -9, -10, and -11 as well as the precursor peptides meet the structural requirements to elicit opioid, immunomodulatory, antioxidative, and satiety functions in newborns.

Circulating Levels of Inflammation and the Effect on Exercise-Related Changes in Bone Mass, Structure and Strength in Middle-Aged and Older Men.

Chronic, low-grade systematic inflammation has been associated with bone loss and increased fracture risk. We previously reported that exercise improved femoral neck bone mineral density (BMD), geometry and strength and lumbar spine trabecular BMD in middle-aged and older men, but had no effect on markers of inflammation. The aim of this study was to examine the association between basal inflammatory status and the adaptive skeletal responses to exercise. Secondary analysis was completed on 91 men aged 50-79 years who participated in an 18-month program of progressive resistance training plus weight-bearing impact exercise (3 day/week) with and without additional calcium-vitamin D3. Markers of inflammation (serum hs-CRP, TNF-α and IL-6) and DXA and QCT-derived BMD, bone structure and strength at the lumbar spine and proximal femur were measured at baseline and 18 months. Multiple regression was used to assess associations between skeletal changes and both baseline levels of individual inflammatory markers and a composite inflammatory index derived from the number of markers categorized into the highest tertile. Baseline serum hs-CRP, TNFα and IL-6 and the composite inflammatory index score were not associated with skeletal changes at any site after adjusting for age, change in lean mass, disease(s)/medication use and adherence to the exercise intervention. In conclusion, this study indicates that basal inflammatory status does not influence the osteogenic response to exercise training in healthy middle-aged and older men.

Dietary Cows' Milk Protein A1 Beta-Casein Increases the Incidence of T1D in NOD Mice.

The contribution of cows' milk containing beta-casein protein A1 variant to the development of type 1 diabetes (T1D) has been controversial for decades. Despite epidemiological data demonstrating a relationship between A1 beta-casein consumption and T1D incidence, direct evidence is limited. We demonstrate that early life exposure to A1 beta-casein through the diet can modify progression to diabetes in non-obese diabetic (NOD) mice, with the effect apparent in later generations. Adult NOD mice from the F0 generation and all subsequent generations (F1 to F4) were fed either A1 or A2 beta-casein supplemented diets. Diabetes incidence in F0⁻F2 generations was similar in both cohorts of mice. However, diabetes incidence doubled in the F3 generation NOD mice fed an A1 beta-casein supplemented diet. In F4 NOD mice, subclinical insulitis and altered glucose handling was evident as early as 10 weeks of age in A1 fed mice only. A significant decrease in the proportion of non-conventional regulatory T cell subset defined as CD4⁺CD25-FoxP3⁺ was evident in the F4 generation of A1 fed mice. This feeding intervention study demonstrates that dietary A1 beta-casein may affect glucose homeostasis and T1D progression, although this effect takes generations to manifest.

Milk Intolerance, Beta-Casein and Lactose.

True lactose intolerance (symptoms stemming from lactose malabsorption) is less common than is widely perceived, and should be viewed as just one potential cause of cows' milk intolerance. There is increasing evidence that A1 beta-casein, a protein produced by a major proportion of European-origin cattle but not purebred Asian or African cattle, is also associated with cows' milk intolerance. In humans, digestion of bovine A1 beta-casein, but not the alternative A2 beta-casein, releases beta-casomorphin-7, which activates µ-opioid receptors expressed throughout the gastrointestinal tract and body. Studies in rodents show that milk containing A1 beta-casein significantly increases gastrointestinal transit time, production of dipeptidyl peptidase-4 and the inflammatory marker myeloperoxidase compared with milk containing A2 beta-casein. Co-administration of the opioid receptor antagonist naloxone blocks the myeloperoxidase and gastrointestinal motility effects, indicating opioid signaling pathway involvement. In humans, a double-blind, randomized cross-over study showed that participants consuming A1 beta-casein type cows' milk experienced statistically significantly higher Bristol stool values compared with those receiving A2 beta-casein milk. Additionally, a statistically significant positive association between abdominal pain and stool consistency was observed when participants consumed the A1 but not the A2 diet. Further studies of the role of A1 beta-casein in milk intolerance are needed.

(1)H-NMR analysis of the human urinary metabolome in response to an 18-month multi-component exercise program and calcium-vitamin-D3 supplementation in older men.

The musculoskeletal benefits of calcium and vitamin-D3 supplementation and exercise have been extensively studied, but the effect on metabolism remains contentious. Urine samples were analyzed by (1)H-NMR spectroscopy from participants recruited for an 18-month, randomized controlled trial of a multi-component exercise program and calcium and vitamin-D3 fortified milk consumption. It was shown previously that no increase in musculoskeletal composition was observed for participants assigned to the calcium and vitamin-D3 intervention, but exercise resulted in increased bone mineral density, total lean body mass, and muscle strength. Retrospective metabolomics analysis of urine samples from patients involved in this study revealed no distinct changes in the urinary metabolome in response to the calcium and vitamin-D3 intervention, but significant changes followed the exercise intervention, notably a reduction in creatinine and an increase in choline, guanidinoacetate, and hypoxanthine (p < 0.001, fold change > 1.5). These metabolites are intrinsically involved in anaerobic ATP synthesis, intracellular buffering, and methyl-balance regulation. The exercise intervention had a marked effect on the urine metabolome and markers of muscle turnover but none of these metabolites were obvious markers of bone turnover. Measurement of specific urinary exercise biomarkers may provide a basis for monitoring performance and metabolic response to exercise regimes.

Energy deficiency, menstrual disturbances, and low bone mass: what do exercising Australian women know about the female athlete triad?

PURPOSE: Prevention of the female athlete triad is essential to protect female athletes' health. The aim of this study was to investigate the knowledge, attitudes, and behaviors of regularly exercising adult women in Australia toward eating patterns, menstrual cycles, and bone health. METHODS: A total of 191 female exercisers, age 18-40 yr, engaging in ≥2 hr/wk of strenuous activity, completed a survey. After 11 surveys were excluded (due to incomplete answers), the 180 participants were categorized into lean-build sports (n = 82; running/athletics, triathlon, swimming, cycling, dancing, rowing), non-lean-build sports (n = 94; basketball, netball, soccer, hockey, volleyball, tennis, trampoline, squash, Australian football), or gym/fitness activities (n = 4). RESULTS: Mean (± SD) training volume was 9.0 ± 5.5 hr/wk, with participants competing from local up to international level. Only 10% of respondents could name the 3 components of the female athlete triad. Regardless of reported history of stress fracture, 45% of the respondents did not think that amenorrhea (absence of menses for ≥3 months) could affect bone health, and 22% of those involved in lean-build sports would do nothing if experiencing amenorrhea (vs. 3.2% in non-lean-build sports, p = .005). Lean-build sports, history of amenorrhea, and history of stress fracture were all significantly associated with not taking action in the presence of amenorrhea (all p < .005). CONCLUSIONS: Few active Australian women are aware of the detrimental effects of menstrual dysfunction on bone health. Education programs are needed to prevent the female athlete triad and ensure that appropriate actions are taken by athletes when experiencing amenorrhea.

Energy deficiency, menstrual disturbances and low bone mass: What do Australian exercising females know about the female athlete triad?

PURPOSE: Prevention of the female athlete triad is essential to protect female athletes' health. The aim of this study was to investigate the knowledge, attitudes and behaviours of regularly exercising adult females towards eating patterns, menstrual cycles and bone health. METHODS: A total of 191 female exercisers, aged 18-40 y, engaging in ≥2 hr/wk of strenuous activity, completed a survey. After excluding 11 surveys (due to incomplete answers), the 180 participants were categorised into lean-build sports (n=82; running/athletics, triathlon, swimming, cycling, dancing, rowing), non lean-build sports (n=94; basketball, netball, soccer, hockey, volleyball, tennis, trampoline, squash, Australian football) or gym/fitness activities (n=4). RESULTS: Mean (±SD) training volume was 9.0±5.5 hr/wk, with participants competing from local up to international level. Only 10% of respondents could name the 3 components of the female athlete triad. Regardless of the reported history of stress fracture, 45% of the respondents did not think that amenorrhoea (absence of menses for ≥ three months) could affect bone health, and 22% of those involved in lean-build sports would do nothing if experiencing amenorrhoea (vs. 3.2% in non lean-build sports, p=0.005). Lean-build sports, history of amenorrhoea and history of stress fracture were all significantly associated with not taking action in the presence of amenorrhoea (all p<0.005). CONCLUSIONS: Few active Australian women are aware of the detrimental effects of menstrual dysfunction on bone health. Education programs are needed to prevent the female athlete triad and ensure appropriate actions are taken by athletes when experiencing amenorrhoea.

Obstacles in the optimization of bone health outcomes in the female athlete triad.

Maintaining low body weight for the sake of performance and aesthetic purposes is a common feature among young girls and women who exercise on a regular basis, including elite, college and high-school athletes, members of fitness centres, and recreational exercisers. High energy expenditure without adequate compensation in energy intake leads to an energy deficiency, which may ultimately affect reproductive function and bone health. The combination of low energy availability, menstrual disturbances and low bone mineral density is referred to as the 'female athlete triad'. Not all athletes seek medical assistance in response to the absence of menstruation for 3 or more months as some believe that long-term amenorrhoea is not harmful. Indeed, many women may not seek medical attention until they sustain a stress fracture. This review investigates current issues, controversies and strategies in the clinical management of bone health concerns related to the female athlete triad. Current recommendations focus on either increasing energy intake or decreasing energy expenditure, as this approach remains the most efficient strategy to prevent further bone health complications. However, convincing the athlete to increase energy availability can be extremely challenging. Oral contraceptive therapy seems to be a common strategy chosen by many physicians to address bone health issues in young women with amenorrhoea, although there is little evidence that this strategy improves bone mineral density in this population. Assessment of bone health itself is difficult due to the limitations of dual-energy X-ray absorptiometry (DXA) to estimate bone strength. Understanding how bone strength is affected by low energy availability, weight gain and resumption of menses requires further investigations using 3-dimensional bone imaging techniques in order to improve the clinical management of the female athlete triad.

Inflammatory cytokine responses to progressive resistance training and supplementation with fortified milk in men aged 50+ years: an 18-month randomized controlled trial.

We examined the effects of progressive resistance training (PRT) and supplementation with calcium-vitamin D(3) fortified milk on markers of systemic inflammation, and the relationship between inflammation and changes in muscle mass, size and strength. Healthy men aged 50-79 years (n = 180) participated in this 18-month randomized controlled trial that comprised a factorial 2 × 2 design. Participants were randomized to (1) PRT + fortified milk supplement, (2) PRT, (3) fortified milk supplement, or (4) a control group. Participants assigned to PRT trained 3 days per week, while those in the supplement groups consumed 400 ml day(-1) of milk containing 1,000 mg calcium plus 800 IU vitamin D(3). We collected venous blood samples at baseline, 12 and 18 months to measure the serum concentrations of IL-6, TNF-α and hs-CRP. There were no exercise × supplement interactions, but serum IL-6 was 29% lower (95% CI, -62, 0) in the PRT group compared with the control group after 12 months. Conversely, IL-6 was 31% higher (95% CI, -2, 65) in the supplement group compared with the non-supplemented groups after 12 and 18 months. These between-group differences did not persist after adjusting for changes in fat mass. In the PRT group, mid-tibia muscle cross-sectional area increased less in men with higher pre-training inflammation compared with those men with lower inflammation (net difference ~2.5%, p < 0.05). In conclusion, serum IL-6 concentration decreased following PRT, whereas it increased after supplementation with fortified milk concomitant with changes in fat mass. Furthermore, low-grade inflammation at baseline restricted muscle hypertrophy following PRT.

Independent and combined effects of calcium-vitamin D3 and exercise on bone structure and strength in older men: an 18-month factorial design randomized controlled trial.

CONTEXT: Exercise and calcium-vitamin D are independently recognized as important strategies to prevent osteoporosis, but their combined effects on bone strength and its determinants remain uncertain. OBJECTIVE: To assess whether calcium-vitamin D(3) fortified milk could enhance the effects of exercise on bone strength, structure, and mineral density in middle-aged and older men. DESIGN, SETTING, PARTICIPANTS: An 18-month factorial design randomized controlled trial in which 180 men aged 50-79 years were randomized to the following: exercise + fortified milk; exercise; fortified milk; or controls. Exercise consisted of progressive resistance training with weight-bearing impact activities performed 3 d/week. Men assigned to fortified milk consumed 400 ml/d of 1% fat milk containing 1000 mg/d calcium and 800 IU/d vitamin D(3). MAIN OUTCOME MEASURES: Changes in bone mineral density (BMD), bone structure, and strength at the lumbar spine (LS), proximal femur, mid-femur, and mid-tibia measured by dual energy x-ray absorptiometry and/or quantitative computed tomography. RESULTS: There were no exercise-by-fortified milk interactions at any skeletal site. Main effect analysis showed that exercise led to a 2.1% (95% confidence interval, 0.5-3.6) net gain in femoral neck section modulus, which was associated with an approximately 1.9% gain in areal BMD and cross-sectional area. Exercise also improved LS trabecular BMD [net gain 2.2% (95% confidence interval, 0.2-4.1)], but had no effect on mid-femur or mid-tibia BMD, structure, or strength. There were no main effects of the fortified milk at any skeletal site. CONCLUSION: A community-based multi-component exercise program successfully improved LS and femoral neck BMD and strength in healthy older men, but providing additional calcium-vitamin D(3) to these replete men did not enhance the osteogenic response.

Effects of lifetime loading history on cortical bone density and its distribution in middle-aged and older men.

We have reported previously that long-term participation of weight-bearing exercise is associated with increased QCT-derived cortical bone size and strength in middle-aged and older men, but not whole bone cortical volumetric BMD. However, since bone remodeling and the distribution of loading-induced strains within cortical bone are non-uniform, the aim of this study was to examine the effects of lifetime loading history on cortical bone mass distribution and bone shape in healthy community dwelling middle-aged and older men. We used QCT to assess mid-femur and mid-tibia angular bone mass distribution around its center (polar distribution), the bone density distribution through the cortex (radial distribution), and the ratio between the maximum and minimum moments of inertia (I(max)/I(min) ratio) in 281 men aged 50 to 79 years. Current (>50 years) and past (13-50 years) sport and leisure time activity was assessed by questionnaire to calculate an osteogenic index (OI) during adolescence and adulthood. All men were then categorized into a high (H) or low/non impact (L) group according to their OI scores in each period. Three contrasting groups were then formed to reflect weight-bearing impact categories during adolescence and then adulthood: H-H, H-L and L-L. For polar bone mass distribution, bone deposition in the anterolateral, medial and posterior cortices were 6-10% greater at the mid-femur and 9-24% greater at mid-tibia in men in the highest compared to lowest tertile of lifetime loading (p<0.01-<0.001). When comparing the influence of contrasting loading history during adolescence and adulthood, there was a graded response between the groups in the distribution of bone mass at the anterior-lateral and posterior regions of the mid-tibia (H-H>H-L>L-L). For radial bone density distribution, there were no statistically significant effects of loading at the mid-femur, but a greater lifetime OI was associated with a non-significant 10-15% greater bone density near the endocortical region of the mid-tibia. In conclusion, a greater lifetime loading history was associated with region-specific adaptations in cortical bone density.

Effects of resistance exercise and fortified milk on skeletal muscle mass, muscle size, and functional performance in middle-aged and older men: an 18-mo randomized controlled trial.

Limited data have suggested that the consumption of fluid milk after resistance training (RT) may promote skeletal muscle hypertrophy. The aim of this study was to assess whether a milk-based nutritional supplement could enhance the effects of RT on muscle mass, size, strength, and function in middle-aged and older men. This was an 18-mo factorial design (randomized control trial) in which 180 healthy men aged 50-79 yr were allocated to the following groups: 1) exercise + fortified milk, 2) exercise, 3) fortified milk, or 4) control. Exercise consisted of progressive RT with weight-bearing impact exercise. Men assigned to the fortified milk consumed 400 ml/day of low-fat milk, providing an additional 836 kJ, 1000 mg calcium, 800 IU vitamin D(3), and 13.2 g protein per day. Total body lean mass (LM) and fat mass (FM) (dual-energy X-ray absorptiometry), midfemur muscle cross-sectional area (CSA) (quantitative computed tomography), muscle strength, and physical function were assessed. After 18 mo, there was no significant exercise by fortified milk interaction for total body LM, muscle CSA, or any functional measure. However, main effect analyses revealed that exercise significantly improved muscle strength ( approximately 20-52%, P < 0.001), LM (0.6 kg, P < 0.05), FM (-1.1 kg, P < 0.001), muscle CSA (1.8%, P < 0.001), and gait speed (11%, P < 0.05) relative to no exercise. There were no effects of the fortified milk on muscle size, strength, or function. In conclusion, the daily consumption of low-fat fortified milk does not enhance the effects of RT on skeletal muscle size, strength, or function in healthy middle-aged and older men with adequate energy and nutrient intakes.

Calcium- and vitamin D3-fortified milk reduces bone loss at clinically relevant skeletal sites in older men: a 2-year randomized controlled trial.

UNLABELLED: In this 2-year randomized controlled study of 167 men >50 years of age, supplementation with calcium-vitamin D3-fortified milk providing an additional 1000 mg of calcium and 800 IU of vitamin D3 per day was effective for suppressing PTH and stopping or slowing bone loss at several clinically important skeletal sites at risk for fracture. INTRODUCTION: Low dietary calcium and inadequate vitamin D stores have long been implicated in age-related bone loss and osteoporosis. The aim of this study was to assess the effects of calcium and vitamin D3 fortified milk on BMD in community living men >50 years of age. MATERIALS AND METHODS: This was a 2-year randomized controlled study in which 167 men (mean age +/- SD, 61.9 +/- 7.7 years) were assigned to receive either 400 ml/day of reduced fat ( approximately 1%) ultra-high temperature (UHT) milk containing 1000 mg of calcium plus 800 IU of vitamin D3 or to a control group receiving no additional milk. Primary endpoints were changes in BMD, serum 25(OH)D, and PTH. RESULTS: One hundred forty-nine men completed the study. Baseline characteristics between the groups were not different; mean dietary calcium and serum 25(OH)D levels were 941 +/- 387 mg/day and 77 +/- 23 nM, respectively. After 2 years, the mean percent change in BMD was 0.9-1.6% less in the milk supplementation compared with control group at the femoral neck, total hip, and ultradistal radius (range, p < 0.08 to p < 0.001 after adjusting for covariates). There was a greater increase in lumbar spine BMD in the milk supplementation group after 12 and 18 months (0.8-1.0%, p < or = 0.05), but the between-group difference was not significant after 2 years (0.7%; 95% CI, -0.3, 1.7). Serum 25(OH)D increased and PTH decreased in the milk supplementation relative to control group after the first year (31% and -18%, respectively; both p < 0.001), and these differences remained after 2 years. Body weight remained unchanged in both groups at the completion of the study. CONCLUSIONS: Supplementing the diet of men >50 years of age with reduced-fat calcium- and vitamin D3-enriched milk may represent a simple, nutritionally sound and cost-effective strategy to reduce age-related bone loss at several skeletal sites at risk for fracture in the elderly.