Nutritional disturbance in acid-base balance and osteoporosis: a hypothesis that disregards the essential homeostatic role of the kidney

Association between dietary acid load and risk of osteoporotic fractures in adults: a systematic review and meta-analysis of observational studies

AIM

We aimed to systematically review and conduct a meta-analysis of the available evidence about the association between dietary acid load (DAL) and fractures in adults.

METHOD

Relevant studies were searched through Web of Science, Scopus, PubMed, and Google Scholar until October 2024. The random-effect model was used to calculate the pooled Odd ratios (OR) and 95% confidence intervals (CIs). Publication bias was evaluated by statistical test of Egger. Subgroup analyses were conducted by study confounders. Moreover, the quality of studies was asessed using the Newcastle Ottawa Scale which is designed for observational studies.

RESULTS

Six studies were included in this review. According to the methodological heterogeneity between studies and their different charactristics, we performed the analysis based on random-effect model that indicated a marginally significant association between DAL and risk of fracture (N event = 5275, Pooled OR: 1.10; 95% CI: 0.99-1.21, P = 0.073) (I2 = 12.9%; P = 0.321). According to subgroup analysis, there was no significant association between DAL and risk of fracture in the cross-sectional effect sizes (N event = 337, OR:0.69; 95%CI:0.47-1.00). There was a significant association between DAL and a greater risk of fracture in cohort studies (N event = 4938, OR:1.12; 95%CI:1.03-1.22, P = 0.006). Also, high-quality studies (OR:1.12; 95%CI:1.03-1.22; P = 0.006) showed a significant association between DAL and fracture risk.

CONCLUSION

DAL was marginally related to a higher risk of fracture. This finding is a trigger for bone health management with a healthy balanced dietary intake.

Exploring high-protein diets in the context of cardiac rehabilitation

The review aims to explore the potential benefit and risk of high-protein diets (HPD) regarding the comorbidity of sarcopoenia and CVD in the setting of cardiac rehabilitation (CR). CR is standard care for individuals who have experienced a cardiac event, but the current practice of predominantly aerobic exercise, a lower-fat diet and weight loss poorly addresses the issue of sarcopoenia. HPD, especially when combined with resistance exercise (RE), may be valuable adjuncts to current CR practice and benefit both muscle and cardiovascular health. Meta-analyses and randomised controlled trials of HPD and CVD risk show beneficial but variable effects regarding weight loss, the lipid profile, insulin resistance and lean body mass in those living with or high risk of CVD. Meta-analyses of prospective cohort studies on hard CVD endpoints favour lower- and plant-protein diets over higher animal protein, but the evidence is inconsistent. HPD augment the strength and muscle gaining benefits of RE in older populations, but there are no published data in those living with CVD providing promising opportunities for CR research. HPD raise concern regarding renal and bone health, the microbiome, branched chain amino acids and environmental sustainability and findings suggest that plant-based HPD may confer ecological and overall health advantages compared to animal-based HPD. However, incorporating RE with HPD might alleviate certain health risks. In conclusion, a largely plant-based HPD is deemed favourable for CR when combined with RE, but further research regarding efficacy and safety in CR populations is needed.

Dietary acidity and bone mass in minority children and adolescents: a cross-sectional analysis from the MetA-Bone trial

Dietary acid load could be associated with bone mass, but there are limited and conflicting results. This secondary cross-sectional analysis evaluated these associations among 123 children/adolescents, mostly Hispanics. Dietary acid load seems to be associated with bone mass in boys, but these results should be confirmed through long-term studies.

BACKGROUND

Childhood/adolescence is key for developing strong bones. With the continuing rise in osteoporosis rates in Western societies, attention has turned to the possible impact of diets that create high levels of acid in the body. Some studies have shown an association between dietary acid load and bone mass, but there are limited studies in children/adolescents and none in Hispanics.

OBJECTIVE

This study aimed to evaluate the associations between dietary acid load (assessed as dietary potential renal acid load, PRAL, and protein to potassium ratio) and whole-body bone mineral content (BMC) and density (BMD) in a sample of 123 children and adolescents of predominantly Hispanic ethnicity.

DESIGN

This study is a secondary cross-sectional analysis.

RESULTS

Dietary PRAL was positively associated with BMC and BMD overall (p < 0.05) and with BMC in boys (p < 0.05) when adjusted for energy misreporting only. The vegetable protein to potassium ratio was inversely associated with BMC (p = 0.004) in boys only, after adjusting for important factors.

CONCLUSIONS

Dietary acid load seems to be associated with BMC in boys in this sample of primarily Hispanic children. Long-term studies are needed to confirm these results and to understand the importance of protein intake in relation to other key nutrients in bone mass acquisition among Hispanic boys.

Association of dietary acid load with inflammatory markers, oxidative stress, and clinical features in patients with knee osteoarthritis

Knee osteoarthritis (KOA) is a prevalent chronic condition characterized by inflammation and oxidative stress, particularly in individuals over 40. Dietary factors, specifically dietary acid load (DAL), may influence these pathological processes. However, the relationship between DAL and inflammatory markers, oxidative stress, and clinical features in patients with KOA remains unexplored. This cross-sectional study involved 147 participants aged 40 and above diagnosed with moderate to severe bilateral primary KOA. Dietary intake was assessed using a validated food frequency questionnaire, and DAL was quantified using Potential Renal Acid Load (PRAL) and Net Endogenous Acid Production (NEAP) indices. Clinical symptoms were evaluated using the WOMAC Index. Biochemical markers of oxidative stress and inflammation were measured from serum samples. Higher PRAL and NEAP scores were associated with increased levels of thiobarbituric acid reactive substances (TBARS) and total oxidant status (TOS), indicating elevated oxidative stress. Additionally, serum levels of inflammatory markers, including TNF-α and hs-CRP, positively correlated with higher DAL scores. Clinical assessments revealed that increased PRAL scores were related to greater severity of symptoms as measured by the WOMAC Index. This study demonstrates a significant association between dietary acid load and markers of inflammation and oxidative stress in KOA patients. These findings suggest that dietary modifications aimed at reducing acid load may serve as a beneficial adjunctive strategy in managing KOA and improving patient outcomes.

Exploring Opportunities to Better Characterize the Effects of Dietary Protein on Health across the Lifespan

Remarkable advances have been made over the last 30 y in understanding the role of dietary protein in optimizing muscle health across the lifespan. That is, acute (<24 h) stable isotope-derived measures of muscle protein synthesis have led to established recommendations for protein quantity, quality, source, and timing of protein ingestion to support muscle health at rest, post exercise, and to overcome age-related anabolic resistance in older adults. Although muscle health is undoubtedly important, moving from muscle to other associated or disease-specific outcomes is a critical next step for the field, given the mounting evidence documenting the effects of dietary protein on measures of chronic disease and age-related decline (for example, cardiovascular disease, type 2 diabetes mellitus, obesity, frailty, and osteoporosis). In this narrative review, we posit that future studies evaluating the potential role of dietary protein build off of the existing knowledge base generated from decades of past research and focus their efforts on closing unanswered knowledge gaps pertaining to dietary protein and health across the lifespan. Throughout this review, we highlight potential methodologies and novel outcome measures that researchers may consider as starting points to facilitate the next 30 y of advances in the field of dietary protein and health.

The association between bone density of lumbar spines and different daily protein intake in different renal function

BACKGROUND

Low protein intake (LPI) has been suggested as a treatment for chronic kidney disease (CKD). However, protein intake is essential for bone health.

METHODS

We studied the database of the National Health and Nutrition Examination Survey, 2005-2010. Basic variables, metabolic diseases, and bone density of different femoral areas were stratified into four subgroups according to different protein intake (DPI) (that is, <0.8, 0.8-1.0, 1.0-1.2, and >1.2 g/kg/day).

RESULTS

Significant differences were found among all lumbar area bone mineral density (BMD) and T-scores (p < 0.0001). There was an apparent trend between a decreasing BMD in the CKD groups with increasing DPI in all single lumbar spines (L1, L2, L3, and L4) and all L spines (L1-L4). Compared with DPI (0.8-1.0 g/day/kg), higher risks of osteoporosis were noticed in the subgroup of >1.2 g/day/kg over L2 (relative risk (RR)=1.326, 95% confidence interval (CI)=1.062-1.656), subgroup >1.2 g/day/kg over L3 (RR = 1.31, 95%CI = 1.057-1.622), subgroup <0.8 g/day/kg over L4 (RR = 1.276, 95%CI = 1.015-1.605), subgroup <0.8 g/day/kg over all L spines (RR = 11.275, 95%CI = 1.051-1.548), and subgroup >1.2 g/day/kg over all L spines (RR = 0.333, 95%CI = 1.098-1.618). However, a higher risk of osteoporosis was observed only in the non-CKD group. There was an apparent trend of higher DPI coexisting with lower BMD and T scores in patients with CKD. For osteoporosis (reference:0.8-1.0 g/day/kg), lower (<0.8 g/day/kg) or higher DPI (>1.2 g/day/kg) was associated with higher risks in the non-CKD group, but not in the CKD group.

CONCLUSIONS

In the CKD group, LPI for renal protection was safe without threatening L spine bone density and without causing a higher risk of osteoporosis.

Nutritional therapy bridges the critical cut-off point for the closed-loop role of type 2 diabetes and bone homeostasis: A narrative review

Currently, osteoporosis-related fractures become the most cutting-edge problem of diabetes-related complications. Rational diet is not only the basis of glycemic management in type 2 diabetes patients, but also the direction of diabetic bone health. This review highlights the importance of micronutrient supplementation (including calcium, magnesium, zinc, vitamin D, vitamin K, and vitamin C) for patients with T2DM, as well as describing the constructive intermediary role of gut flora between T2DM and bone through nutrients predominantly high in dietary fiber. In addition, it is recommended to combine the Mediterranean dietary pattern with other diversified management approaches to prevent OP. Therefore, this provides a theoretical basis for the potential role of islet β-cells in promoting bone health.

Novel Near-Infrared-II In Vivo Visualization Revealed Rapid Calcium Intestine Turnover in Daphnia magna with Delayed Impact by Cadmium and Acidification

Calcium is a highly demanded metal, and its transport across the intestine of Daphnia magna remains a significant unresolved question. Due to technical constraints, the visualization of the kinetic process of Ca passage through D. magna has been challenging. Here, we developed the second near-infrared Ca sensor (NIR-II Ca) and conducted real-time in vivo imaging of Ca in daphnids with a high signal-to-noise ratio, deep tissue penetration, and minimal damage. Through the utilization of the NIR-II Ca sensor, we for the first time visualized and quantified the kinetic process of Ca passage in the intestine in real time. The results revealed that trophically available Ca passed through the intestines in 24 h, whereas waterborne Ca required only 35 min. This rapid "flushing through" mechanism established waterborne Ca as the primary source of Ca absorption. However, environmental stressors such as water acidification and cadmium significantly delayed the Ca passage and absorption. The development of NIR imaging and sensors allows for real-time dynamic visualization of contaminants/nutrients in organisms and holds great potential as a powerful tool for future studies into material kinetic processes in living animals.

Nutritional strategies to optimise musculoskeletal health for fall and fracture prevention: Looking beyond calcium, vitamin D and protein

Falls and osteoporotic fractures are a major public health problem, particularly among older adults. A third of individuals aged 65 years and over fall at least once each year, with up to 20 % of these resulting in serious injury, including fracture. In conjunction with regular exercise, the importance of diet for musculoskeletal health has largely focused upon calcium, vitamin D, and protein, particularly in the context of preventing falls and fractures. Whilst there is evidence for the benefits of these nutrients for musculoskeletal health, other aspects of the diet remain largely underexplored. For example, vegetables are rich sources of macro- and micronutrients that are essential for muscle function and bone health, which are key factors in the prevention of falls and fractures. Recent work has highlighted the importance of nutrients such as vegetable-derived nitrate and vitamin K1 in optimising muscle strength, physical function, and bone quality. In the context of dietary patterns, vegan/plant-based diets have recently gained popularity due to perceived health benefits, animal welfare, or to tackle climate change. The elimination and/or substitution of animal-based products for plant foods (without careful planning and/or expert dietary guidance) could, however, have long-term negative musculoskeletal consequences; a trend uncovered by recent evidence. Within the overarching theme of nutrition for fall and fracture prevention in older populations, the aim of this review is to (i) summarise the current evidence for calcium, vitamin D and protein; (ii) describe the importance of vegetables and selected nutrients, such as nitrate and vitamin K1, for muscle function and bone structural integrity; and (iii) highlight current evidence around different dietary patterns (e.g., plant-based, diet quality, data driven approaches) and their impact on musculoskeletal health.

Exploring the use of alternative diets in people living with cancer

There is significant use of alternative diets by people living with cancer, with data suggesting this has continued to increase since the 1980s. Commonly used alternative diets include the ketogenic diet, Gerson therapy, alkaline diets and fasting diets. This article explains the latest trends in relation to alternative diets, discusses the reasons why people may want to use these and examines their hypothesised mechanisms of action. The author outlines and critically reviews the evidence underpinning the use of such diets in those living with cancer, and suggests that this remains weak. The article also explores the challenges that nurses may experience when a person living with cancer wishes to adopt an alternative diet, and provides practical advice and recommendations on nutrition.

Modifiable risk factors for bone health & fragility fractures

Osteoporosis is an ageing disorder characterised by poor microstructural architecture of the bone and an increase in the risk of fragility fractures, which often leads to hospitalisation and eventually a loss of mobility and independence. By 2050, it is estimated that more than 30 million people in Europe will be affected by bone diseases, and European hospitalisation alone can approximately cost up to 3.5 billion euros each year [1]. Although inherited variation in bone mineral density (BMD) is pre-determined by up to 85% [2], there is a window of opportunity to optimise BMD and reduce fracture risk through key modifiable lifestyle factors during the life course. An optimal diet rich in micronutrients, such as calcium, vitamin D, and potassium, has long been considered an important modifiable component of bone health, which is attributed to their direct roles within bone metabolism. Recently, there has been emerging evidence to suggest that protein and even an adequate intake of fruit and vegetables may also play an important role in improving BMD [3,4]. Maintaining a physically active lifestyle is not only protective from non-communicable diseases such as cardiovascular disease but it also has been shown to lessen the risk of fractures later in life, thereby making it an imperative modifiable factor for bone health, particularly as it also supports peak bone mass attainment during childhood/adolescence and can facilitate the maintenance of bone mass throughout adulthood [5]. Other key lifestyle factors that could be potentially modified to reduce the risk of osteoporosis or osteoporotic fractures later in life include smoking status, alcohol intake, and body composition [6]. Therefore, the principle aim of this review is to highlight the recent evidence pertaining to modifiable lifestyle factors that contribute to optimal bone health and the prevention of fragility fractures in later life.

Dietary Acid Load and Bone Health: A Systematic Review and Meta-Analysis of Observational Studies

Findings on the association between dietary acid load (DAL) and bone health are conflicting. This study aimed to summarize available studies on the association between DAL and risk of fractures or bone mineral density (BMD) in adults. Online databases including PubMed, Scopus, and Embase were searched for relevant studies published up to June 2021, using pertinent keywords. We identified observational studies (cohort, case-control, and cross-sectional) investigating the association between DAL and risk of fractures or BMD, then selected studies following these reported criteria: RRs with corresponding 95% CIs for the relationship between DAL and fracture risk; correlation coefficients for the association between DAL and BMD; and mean ± SD of BMD values across the categories of DAL. Overall, 17 studies with 80545 individuals were included. There was no significant relationship between the PRAL and fracture risk (Pooled RR: 1.18; 95% confidence interval 0.98 to 1.41, I² = 60.6%). Moreover, a similar association was observed between the NEAP and fracture risk (Pooled RR: 1.41, 95% CI: 0.79 to 2.52, I² = 54.1%). The results of five studies from four publications revealed no significant association between dietary PRAL score and femoral and spinal BMD (WMD femoral = −0.01, 95% confidence interval: −0.02 to 0.01, I² = 76.5%; WMD spinal = −0.01, 95% CI: −0.03 to 0.01, I² = 56.7%). However, being in the highest category of NEAP was significantly associated with a lower femoral and spinal BMD (WMD femoral = −0.01, 95% CI: −0.02 to −0.00, I² = 82.1%; WMD spinal = −0.02, 95% CI: −0.03 to −0.01, I² = 93%). It was showed that adopting diets high in acidity was not associated with risk of fractures. We also found a significant negative relationship between NEAP and BMD. However, DAL based on PRAL was not associated with BMD.

Milk proteins and their derived peptides on bone health: Biological functions, mechanisms, and prospects

Bone is a dynamic organ under constant metabolism (or remodeling), where a delicate balance between bone resorption and bone formation is maintained. Disruption of this coordinated bone remodeling results in bone diseases, such as osteoporosis, the most common bone disorder characterized by decreased bone mineral density and microarchitectural deterioration. Epidemiological and clinical evidence support that consumption of dairy products is beneficial for bone health; this benefit is often attributed to the presence of calcium, the physiological contributions of milk proteins on bone metabolism, however, are underestimated. Emerging evidence highlighted that not only milk proteins (including individual milk proteins) but also their derived peptides positively regulate bone remodeling and attenuate bone loss, via the regulation of cellular markers and signaling of osteoblasts and osteoclasts. This article aims to review current knowledge about the roles of milk proteins, with an emphasis on individual milk proteins, bioactive peptides derived from milk proteins, and effect of milk processing in particular fermentation, on bone metabolism, to highlight the potential uses of milk proteins in the prevention and treatment of osteoporosis, and, to discuss the knowledge gap and to recommend future research directions.

Associations between age-related changes in bone microstructure and strength and dietary acid load in a cohort of community-dwelling, healthy men and postmenopausal women

BACKGROUND

The importance of dietary acid load (DAL) in the pathogenesis of osteoporosis is still debated. Age-related changes in bone microstructure and strength in relation to DAL remain largely unexplored.

OBJECTIVES

We investigated the associations between changes in areal and volumetric bone mineral density (BMD), bone microstructure and strength, fracture risk, and DAL in a prospective cohort of 65-y-old healthy men and postmenopausal women.

METHODS

Potential renal acid load (PRAL; mEq/d) was calculated as a DAL proxy to characterize participants' diet as alkaline (Alk-D; PRAL < -5), neutral (Neut-D; -5 ≤ PRAL ≤ 5), or acidic (Acid-D; PRAL >5). We measured areal BMD (aBMD) by DXA, and distal radius and tibia bone microstructure using high-resolution peripheral quantitative computed tomography, at baseline (n = 853) and after 6.1 ± 1.4 y (n = 708). Bone strength was estimated using finite element analyses at baseline and after 3.0 ± 0.5 y (n = 613). Prevalent and incident fractures were recorded.

RESULTS

The majority of the participants (59%) had an Alk-D, while 23% had a Neut-D, and 18% an Acid-D. Baseline aBMD and bone microstructure and strength did differ or were slightly better in women or men with an Acid-D versus those consuming an Alk-D or Neut-D. Indeed, women with an Acid-D had higher trabecular number (P = 0.010 vs. Alk-D; P = 0.001 vs. Neut-D), while men had higher hip and radius aBMD (P = 0.008 and 0.024 vs. Neut-D, respectively) and radius strength (P = 0.026 vs. Neut-D). Over the follow-up, women in the Acid-D group experienced lower cortical and endocortical bone loss at the radius than did the Alk-D and Neut-D groups (cortical thickness, P = 0.008 and < 0.001; trabecular area, P = 0.001 and < 0.001, respectively). No association between fractures and PRAL was observed.

CONCLUSIONS

These null or favourable associations between baseline values or changes in aBMD, bone microstructure and strength, and DAL in this cohort of 65-y-old healthy individuals do not support adverse DAL-mediated effects on bone. This trial was registered at http://www.isrctn.com as ISRCTN11865958.

Nutrients and Dietary Patterns Related to Osteoporosis

Osteoporosis is a common chronic disease characterized by a decrease in bone mineral density, impaired bone strength, and an increased risk of fragility fractures. Fragility fractures are associated with significant morbidity, mortality and disability and are a major public health problem worldwide. The influence of nutritional factors on the development and progression of this disease can be significant and is not yet well established. Calcium intake and vitamin D status are considered to be essential for bone metabolism homeostasis. However, some recent studies have questioned the usefulness of calcium and vitamin D supplements in decreasing the risk of fractures. The adequate intake of protein, vegetables and other nutrients is also of interest, and recommendations have been established by expert consensus and clinical practice guidelines. It is important to understand the influence of nutrients not only in isolation but also in the context of a dietary pattern, which is a complex mixture of nutrients. In this review, we evaluate the available scientific evidence for the effects of the main dietary patterns on bone health. Although some dietary patterns seem to have beneficial effects, more studies are needed to fully elucidate the true influence of diet on bone fragility.

Role of Citrate in Pathophysiology and Medical Management of Bone Diseases

Citrate is an intermediate in the "Tricarboxylic Acid Cycle" and is used by all aerobic organisms to produce usable chemical energy. It is a derivative of citric acid, a weak organic acid which can be introduced with diet since it naturally exists in a variety of fruits and vegetables, and can be consumed as a dietary supplement. The close association between this compound and bone was pointed out for the first time by Dickens in 1941, who showed that approximately 90% of the citrate bulk of the human body resides in mineralised tissues. Since then, the number of published articles has increased exponentially, and considerable progress in understanding how citrate is involved in bone metabolism has been made. This review summarises current knowledge regarding the role of citrate in the pathophysiology and medical management of bone disorders.

Protein and bone health across the lifespan

Bone health is determined by the rate of accrual in early life, followed by the rate of age-associated bone loss. Dietary protein intake might have a role in bone health across both of these phases via pleiotropic mechanistic pathways. Herein we summarise the pathways through which protein may exert either a positive or negative influence on bone. In the introduction, we describe the acid-ash hypothesis, which states that a high-protein intake may lead to an acidic residue that must be neutralised through the leaching of calcium and other minerals from the bone, subsequently leading to demineralisation and bone weakening. Conversely, and as described in the 'Against: mechanisms through which protein may negatively impact bone' section, protein intake may act to strengthen the bone by stimulating the activity of various anabolic hormones and growth factors, or by optimising muscle mass and functionality, which itself has an osteogenic influence. The net effect of these contrasting pathways is described in the 'For: mechanisms through which protein may positively impact bone' section, where a number of meta-analyses have demonstrated that higher protein intakes have a small positive impact on bone mass and fracture risk. Sometimes higher than recommended protein intakes are advised, e.g. during the earlier and later phases of the lifespan or during reduced energy availability. We conclude that protein is an essential nutrient for bone health, although further research is required to clarify the mechanistic pathways through which it exerts its influence, along with the clarification of the quantities, food sources and timing to allow for the optimisation of this protective influence and ultimately a reduction in fracture risk.

Mineral bone disorders in chronic kidney disease

As the GFR loss aggravates, the disturbed mineral metabolism worsens the bone microstructure and remodelling - scenario, which is known as CKD-mineral bone disease (MBD). CKD-MBD is characterized by : (i) abnormal metabolism of calcium, phosphorus, parathyroid hormone (PTH), or vitamin D; (ii) abnormalities in bone turnover, mineralization, volume linear growth or strength; (iii) soft-tissue calcifications, either vascular or extra-osseous. Uremic vascular calcification and osteoporosis are the most common complications related to CKD-MBD. Disregulated bone turnover by uremic toxin or secondary hyperparathyroidism disturbed bone mineralization and makes it difficult for calcium and inorganic phosphate to enter into bone, resulting in increased serum calcium and inorganic phosphate. Vascular calcification worsens by hyperphosphatemia and systemic inflammation. Since vitamin D deficiency plays an important role in renal osteodystrophy, supplement of nutritional vitamin D is important in treating uremic osteoporosis and vascular calcification at the same time. Its pleotropic effect improves the bone remodeling initiated by osteoblast and alleviates the risk factors for vascular calcification with less hypercalcemia than vitamin D receptor analogs. Therefore, nutritional vitamin D should be considered in managing CKDMBD.

Potassium Citrate Supplementation Decreases the Biochemical Markers of Bone Loss in a Group of Osteopenic Women: The Results of a Randomized, Double-Blind, Placebo-Controlled Pilot Study

The relationship involving acid-base imbalance, mineral metabolism and bone health status has previously been reported but the efficacy of the alkalizing supplementation in targeting acid overload and preventing bone loss has not yet been fully elucidated. In this randomized, double-blind, placebo-controlled study, the hypothesis that potassium citrate (K citrate) modifies bone turnover in women with postmenopausal osteopenia was tested. Three hundred and ten women were screened; 40 women met the inclusion criteria and were randomly assigned to the treatment or the placebo group. They were treated with K citrate (30 mEq day⁻¹) or a placebo in addition to calcium carbonate (500 mg day⁻¹) and vitamin D (400 IU day⁻¹). At baseline and time points of 3 and 6 months, serum indicators of renal function, electrolytes, calciotropic hormones, serum bone turnover markers (BTMs) (tartrate-resistant acid phosphatase 5b (TRACP5b), carboxy-terminal telopeptide of type I collagen (CTX), bone alkaline phosphatase (BAP), procollagen type 1 N terminal propeptide (PINP)), and urine pH, electrolytes, and citrate were measured. The follow-up was completed by 17/20 patients in the “K citrate” group and 18/20 patients in the “placebo” group. At baseline, 90% of the patients exhibited low potassium excretion in 24 h urine samples, and 85% of cases had at least one urine parameter associated with low-grade acidosis (low pH, low citrate excretion). After treatment, CTX and BAP decreased significantly in both groups, but subjects with evidence of low-grade acidosis gained significant benefits from the treatment compared to the placebo. In patients with low 24h-citrate excretion at baseline, a 30% mean decrease in BAP and CTX was observed at 6 months. A significant reduction was also evident when low citrate (BAP: −25%; CTX: −35%) and a low pH (BAP: −25%; CTX: −30%) were found in fasting-morning urine. In conclusion, our results suggested that K citrate supplementation improved the beneficial effects of calcium and vitamin D in osteopenic women with a documented potassium and citrate deficit, and a metabolic profile consistent with low-grade acidosis.

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.

Prediction of Renal Acid Load in Adult Patients on Parenteral Nutrition

Metabolic acidosis and metabolic bone disease are frequent complications in patients on parenteral nutrition (PN). A common contributor to these complications could be a daily high renal acid load. This study aims to find a method for predicting the potential total acid load (PTAL) and the pH of the compounded parenteral nutrition mixtures. The pH and titratable acidity (TA) of fifty compounded mixtures were measured. The potential metabolic acid load (PMAL) was calculated by considering the amount of nutrients that are acid producers and consumers. The PTAL of the TPN mixtures was calculated by adding TA to PMAL. Multiple linear regression analyses were used to develop a predictive model for the TA and pH of the compounded mixtures. The predicted TA and pH values of the analyzed mixtures agreed with those measured (Passing-Bablok analysis). The PTAL was >50 mmol/day for 82% of the mixtures, >75 mmol/day for 40% of the mixtures, and >100 mmol/day for 22% of the mixtures. The prediction of the renal acid load in patients on long-term PN could allow more appropriate acid-base balancing. Moreover, predicting the pH of such mixtures could be useful to pharmacists to assess the stability and compatibility of the components in the compounded mixtures.

Animal versus plant protein and adult bone health: A systematic review and meta-analysis from the National Osteoporosis Foundation

Background

Protein may have both beneficial and detrimental effects on bone health depending on a variety of factors, including protein source.

Objective

The aim was to conduct a systematic review and meta-analysis evaluating the effects of animal versus plant protein intake on bone mineral density (BMD), bone mineral content (BMC) and select bone biomarkers in healthy adults.

Methods

Searches across five databases were conducted through 10/31/16 for randomized controlled trials (RCTs) and prospective cohort studies in healthy adults that examined the effects of animal versus plant protein intake on 1) total body (TB), total hip (TH), lumbar spine (LS) or femoral neck (FN) BMD or TB BMC for at least one year, or 2) select bone formation and resorption biomarkers for at least six months. Strength of evidence (SOE) was assessed and random effect meta-analyses were performed.

Results

Seven RCTs examining animal vs. isoflavone-rich soy (Soy+) protein intake in 633 healthy peri-menopausal (n = 1) and post-menopausal (n = 6) women were included. Overall risk of bias was medium. Limited SOE suggests no significant difference between Soy+ vs. animal protein on LS, TH, FN and TB BMD, TB BMC, and bone turnover markers BSAP and NTX. Meta-analysis results showed on average, the differences between Soy+ and animal protein groups were close to zero and not significant for BMD outcomes (LS: n = 4, pooled net % change: 0.24%, 95% CI: -0.80%, 1.28%; TB: n = 3, -0.24%, 95% CI: -0.81%, 0.33%; FN: n = 3, 0.13%, 95% CI: -0.94%, 1.21%). All meta-analyses had no statistical heterogeneity.

Conclusions

These results do not support soy protein consumption as more advantageous than animal protein, or vice versa. Future studies are needed examining the effects of different protein sources in different populations on BMD, BMC, and fracture.

[Dietary acid load: A novel target for the nephrologist?]

The acid production of endogenous origin depends mainly on the metabolism of the food and varies with the nature of these. Of the order of 1mEq/kg/day for contemporary food in industrialized countries, it is reduced by more than one third among vegetarians and close to neutrality among vegans. The dietary acid load is eliminated by the normal kidneys, thus maintaining the acid-base equilibrium. In the setting of CKD, it will overflow the capacities of the nephrons, generating a retention of H+ ions, promoting subclinical acidosis. This tissue retention of H+ ions was confirmed by direct techniques in animal models and indirect techniques in humans. The systemic retention of H+ ions and the accompanying compensatory mechanisms have negative consequences on bone tissue, skeletal muscle, cardiovascular risk and renal function. In the animal, the substitution of casein (acid) by soy (alkaline) prevents metabolic acidosis and slows the progression of renal insufficiency. In man, various prospective studies have confirmed that the risk of renal insufficiency was positively correlated with the dietary acid load. Conversely, bicarbonate supplementation and/or a diet enriched with fruits and vegetables, have a favorable effect on renal insufficiency, including in subjects with normal bicarbonate. These results lead to reconsider the K/DOQI recommendations to correct acidosis when the bicarbonate level falls below 22mEq/L, since tissue retention of H+ ions and its negative consequences appear at higher or even normal levels of bicarbonates.

Western diets are not responsible for chronic acid retention: a critical analysis of organic acid and phosphate contribution

According to usual literature, the diet-dependent endogenous production of titratable acidity (TA) is contributed by sulphuric and phosphoric acids (NA) and by metabolizable acids (MAs), representing 'net-endogenous acid production' (NEAP). NEAP is mainly neutralised by diet-dependent [Formula: see text] salts of inorganic cations ([Formula: see text]), estimated in foods, faeces and urine from inorganic cation-anion difference (NB). It is claimed that urinary loss of organic acids' anions, '[Formula: see text]', induces metabolizable H⁺ ions' retention. Since '[Formula: see text]' is normally lost in urine as '[Formula: see text]' or '[Formula: see text]', no MA retention takes place. Therefore, in our approach, net acid production (NAP) reduces to endogenous sulphuric acidity only. Since in western diets (WDs) alkaline cations exceed inorganic anions (NB excess), acid excess from phosphorus is neutralized. Moreover, the renal reabsorption of ultra-filtered Pi takes place at [Formula: see text] ratios greater than '4/1', which means that the kidney operates as a dietary Pi-dependent NB generator ([Formula: see text] or [Formula: see text]). Since, in standard WDs, H₂SO₄ generation is less than '[Formula: see text]' production, the sulphuric acidity escaping the intestinal [Formula: see text] absorption is neutralized by [Formula: see text] and excreted as diet-dependent [Formula: see text], without interfering in normal A/B status. Only when extreme acidifying diets are ingested, sulphuric acidity may exceed '[Formula: see text]'. In this case, the excess of sulphuric acidity production is neutralised by the intervention of urinary [Formula: see text] excretion, whose employment is normally restricted to prevent loss of ultra-filtered NB. Finally, the whole body NA balance (NAb(W)) is calculated from the difference 'NA_abs - NA(u)', where abs = intestinal absorption and u = urinary excretion. Being 'NA_abs ≈ NA(u)', NAb(W) approximates zero, confirming WDs as non-acidifying foods.

Dietary acid load, trabecular bone integrity, and mineral density in an ageing population: the Rotterdam study

We studied the relation between a diet that is high in acid-forming nutrients (e.g. proteins) and low in base-forming nutrients (e.g. potassium) and bone structure. We showed a negative relation, which was more prominent if proteins were of animal rather than of vegetable origin and if intake of dietary fibre was high.

INTRODUCTION

Studies on dietary acid load (DAL) and fractures have shown inconsistent results. Associations between DAL, bone mineral density (BMD) and trabecular bone integrity might play a role in these inconsistencies and might be influenced by renal function and dietary fibre intake. Therefore, our aim was to study (1) associations of DAL with BMD and with the trabecular bone score (TBS) and (2) the potential influence of renal function and dietary fibre in these associations.

METHODS

Dutch individuals aged 45 years and over (n = 4672) participating in the prospective cohort of the Rotterdam study were included. Based on food frequency questionnaires, three indices of DAL were calculated: the net endogenous acid production (NEAP) and the ratios of vegetable or animal protein and potassium (VegPro/K and AnPro/K). Data on lumbar spinal TBS and BMD were derived from dual-energy X-ray absorptiometry measurements.

RESULTS

Independent of confounders, NEAP and AnPro/K, but not VegPro/K, were associated with low TBS (standardized β (95%) = -0.04 (-0.07, -0.01) and -0.08 (-0.11, -0.04)) but not with BMD. Associations of AnPro/K and VegPro/K with TBS were non-linear and differently shaped. Unfavourable associations between NEAP, BMD and TBS were mainly present in subgroups with high fibre intake.

CONCLUSIONS

High NEAP was associated with low TBS. Associations of AnPro/K and VegPro/K and TBS were non-linear and differently shaped. No significant associations of DAL with BMD were observed, nor was there any significant interaction between DAL and renal function. Mainly in participants with high intake of dietary fibre, DAL might be detrimental to bone.

Potassium citrate prevents increased osteoclastogenesis resulting from acidic conditions: Implication for the treatment of postmenopausal bone loss

The extracellular acidic milieu in bones results in activation of osteoclasts (OC) and inhibition of osteoblasts (OB) causing a net loss of calcium from the skeleton and the deterioration of bone microarchitecture. Alkalinization through supplementation with potassium citrate (K citrate) has been proposed to limit the osteopenia progression, even though its pharmacological activity in bone microenvironment is not well defined. We evaluated if K citrate was able to prevent the adverse effects that acidic milieu induces on bone cells. OC and OB were maintained in neutral (pH 7.4) versus acidic (pH 6.9) culture medium, and treated with different K citrate concentrations. We evaluated the OC differentiation at seven days, by counting of multinucleated cells expressing tartrate-resistant acid phosphatase, and the activity of mature OC at 14 days, by quantifying of collagen degradation. To evaluate the effects on OB, we analyzed proliferation, mineralization, and expression of bone-related genes. We found that the low pH increased OC differentiation and activity and decreased OB function. The osteoclastogenesis was also promoted by RANKL concentrations ineffective at pH 7.4. Non-cytotoxic K citrate concentrations were not sufficient to steadily neutralize the acidic medium, but a) inhibited the osteoclastogenesis, the collagen degradation, and the expression of genes involved in RANKL-mediated OC differentiation, b) enhanced OB proliferation and alkaline phosphatase expression, whereas it did not affect the in vitro mineralization, and c) were effective also in OC cultures resistant to alendronate, i.e. the positive control of osteoclastogenesis inhibition. In conclusion, K citrate prevents the increase in OC activity induced by the acidic microenvironment, and the effect does not depend exclusively on its alkalizing capacity. These data provide the biological basis for the use of K citrate in preventing the osteopenia progression resulting from low-grade acidosis.

Nutrition and osteoporosis prevention for the orthopaedic surgeon: A wholefoods approach

Osteoporosis is a prevalent and debilitating condition with no signs of subsiding. Rising numbers of people consuming nutrient-poor diets coupled with ageing populations and sedentary lifestyles appear to be the main drivers behind this.

While the nutrients calcium and vitamin D have received most attention, there is growing evidence that wholefoods and other micronutrients have roles to play in primary and potentially secondary osteoporosis prevention.

Until recently, calcium and vitamin D were regarded as the main nutrients essential to bone health but now there are emerging roles for iron, copper and selenium, among others.

Fruit and vegetables are still not being eaten in adequate amounts and yet contain micronutrients and phytochemicals useful for bone remodelling (bone formation and resorption) and are essential for reducing inflammation and oxidative stress.

There is emerging evidence that dried fruits, such as prunes, provide significant amounts of vitamin K, manganese, boron, copper and potassium which could help to support bone health.

Just 50 g of prunes daily have been found to reduce bone resorption after six months when eaten by osteopaenic, postmenopausal women.

Dairy foods have an important role in bone health. Carbonated drinks should not replace milk in the diet.

A balanced diet containing food groups and nutrients needed for bone health across the whole lifecycle may help to prevent osteoporosis.

Greater efforts are needed to employ preventative strategies which involve dietary and physical activity modifications, if the current situation is to improve.

Cite this article: EFORT Open Rev 2017;2:300-308. DOI: 10.1302/2058-5241.2.160079

The dietary protein, IGF-I, skeletal health axis

Dietary protein represents an important nutrient for bone health and thereby for the prevention of osteoporosis. Besides its role as a brick provider for building the organic matrix of skeletal tissues, dietary protein stimulates the production of the anabolic bone trophic factor IGF-I (insulin-like growth factor I). The liver is the main source of circulating IGF-I. During growth, protein undernutrition results in reduced bone mass and strength. Genetic defect impairing the production of IGF-I markedly reduces bone development in both length and width. The serum level of IGF-I markedly increases and then decreases during pubertal maturation in parallel with the change in bone growth and standing height velocity. The impact of physical activity on bone structure and strength is enhanced by increased dietary protein consumption. This synergism between these two important environmental factors can be observed in prepubertal boys, thus modifying the genetically determined bone growth trajectory. In anorexia nervosa, IGF-I is low as well as bone mineral mass. In selective protein undernutrition, there is a resistance to the exogenous bone anabolic effect of IGF-I. A series of animal experiments and human clinical trials underscore the positive effect of increased dietary intake of protein on calcium-phosphate economy and bone balance. On the contrary, the dietary protein-induced acidosis hypothesis of osteoporosis is not supported by several experimental and clinical studies. There is a direct effect of amino acids on the local production of IGF-I by osteoblastic cells. IGF-I is likely the main mediator of the positive effect of parathyroid hormone (PTH) on bone formation, thus explaining the reduction in fragility fractures as observed in PTH-treated postmenopausal women. In elderly women and men, relatively high protein intake protects against spinal and femoral bone loss. In hip fracture patients, isocaloric correction of the relatively low protein intake results in: increased IGF-I serum level, significant attenuation of postsurgical bone loss, improved muscle strength, better recovery, and shortened hospital stay. Thus, dietary protein contributes to bone health from early childhood to old age. An adequate intake of protein should be recommended in the prevention and treatment of osteoporosis.

Food fortification for bone health in adulthood: a scoping review

Food fortification can deliver essential micronutrients to large population segments without modifications in consumption pattern, suggesting that fortified foods may be formulated for populations at risk for fragility fractures. This scoping review determined the extent to which randomized controlled studies have been carried out to test the impact of fortified foods on bone outcomes, searching PubMed for all studies using the terms 'fortified AND bone', and 'fortification AND bone'. Studies were restricted to English language, published between 1996 and June 2015. From 360 articles, 24 studies met the following criteria: human study in adults ⩾18 years (excluding pregnancy or lactation); original study of a fortified food over time, with specific bone outcomes measured pre- and post intervention. Six studies involved adults <50 years; 18 involved adults ⩾50 years. Singly or in combination, 17 studies included calcium and 16 included vitamin D. There were 1 or 2 studies involving either vitamin K, magnesium, iron, zinc, B-vitamins, inulin or isoflavones. For adults <50 years, the four studies involving calcium or vitamin D showed a beneficial effect on bone remodeling. For adults ⩾50 years, n=14 provided calcium and/or vitamin D, and there was a significant bone turnover reduction. No consistent effects were reported in studies in which addition of vitamin K, folic acid or isoflavone was assessed. Results from this scoping review indicate that up to now most studies of fortification with bone health have evaluated calcium and/or vitamin D and that these nutrients show beneficial effects on bone remodeling.

Draining and salting as responsible key steps in the generation of the acid-forming potential of cheese: Application to a soft blue-veined cheese

A disregarded nutritional feature of cheeses is their high acid-forming potential when ingested, which is associated with deleterious effects on consumers' health. This work aimed to characterize the acid-forming potential of a blue-veined cheese during manufacturing to identify the main steps of the process involved in this phenomenon. Sampling was performed on 3 batches at 10 steps of the cheese-making process: reception of raw milk, pasteurization, maturation of milk, coagulation, stirring, draining of the curds, and 4 ripening stages: 21, 28, 42, and 56d. The acid-forming potential of each sample was evaluated by (1) the calculation of the potential renal acid load (PRAL) index (considering protein, Cl, P, Na, K, Mg, and Ca contents), and (2) its organic anion content (lactate and citrate), considered as alkalinizing elements. Draining and salting were identified as the main steps responsible for generation of the acid-forming potential of cheese. The draining process induced an increase in the PRAL index from 1.2mEq/100g in milk to 10.4mEq/100g in drained curds due to the increase in dry matter and the loss of alkaline minerals into the whey. The increase in PRAL value (20.3mEq/100g at d 56) following salting resulted from an imbalance between the strong acidogenic elements (Cl, P, and proteins) and the main alkalinizing ones (Na and Ca). Particularly, Cl had a major effect on the PRAL value. Regarding organic anions, draining induced a loss of 93% of the citrate content in initial milk. The lactate content increased as fermentation occurred (1,297.9mg/100g in drained curds), and then decreased during ripening (519.3mg/100g at d 56). This lactate level probably helps moderate the acidifying potential of end products. Technological strategies aimed at limiting the acid-forming potential of cheeses are proposed and deserve further research to evaluate their nutritional relevance.

Effects of Dairy Products Consumption on Health: Benefits and Beliefs--A Commentary from the Belgian Bone Club and the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases

Dairy products provide a package of essential nutrients that is difficult to obtain in low-dairy or dairy-free diets, and for many people it is not possible to achieve recommended daily calcium intakes with a dairy-free diet. Despite the established benefits for bone health, some people avoid dairy in their diet due to beliefs that dairy may be detrimental to health, especially in those with weight management issues, lactose intolerance, osteoarthritis, rheumatoid arthritis, or trying to avoid cardiovascular disease. This review provides information for health professionals to enable them to help their patients make informed decisions about consuming dairy products as part of a balanced diet. There may be a weak association between dairy consumption and a possible small weight reduction, with decreases in fat mass and waist circumference and increases in lean body mass. Lactose intolerant individuals may not need to completely eliminate dairy products from their diet, as both yogurt and hard cheese are well tolerated. Among people with arthritis, there is no evidence for a benefit to avoid dairy consumption. Dairy products do not increase the risk of cardiovascular disease, particularly if low fat. Intake of up to three servings of dairy products per day appears to be safe and may confer a favourable benefit with regard to bone health.

Pre-Osteoarthritis: Definition and Diagnosis of an Elusive Clinical Entity

OBJECTIVE

An attempt to define pre-osteoarthritis (OA) versus early OA and definitive osteoarthritis.

METHODS

A group of specialists in the field of cartilage science and treatment was formed to consider the nature of OA onset and its possible diagnosis.

RESULTS

Late-stage OA, necessitating total joint replacement, is the end stage of a biological process, with many previous earlier stages. Early-stage OA has been defined and involves structural changes identified by arthroscopy or radiography. The group argued that before the "early-stage OA" there must exist a stage where cellular processes, due to the presence of risk factors, have kicked into action but have not yet resulted in structural changes. The group suggested that this stage could be called "pre-osteoarthritis" (pre-OA).

CONCLUSIONS

The group suggests that defining points of initiation for OA in the knee could be defined, for example, by traumatic episodes or surgical meniscectomy. Such events may set in motion metabolic processes that could be diagnosed by modern MRI protocols or arthroscopy including probing techniques before structural changes of early OA have developed. Preventive measures should preferably be applied at this pre-OA stage in order to stop the projected OA "epidemic."

A look behind the scenes: the risk and pathogenesis of primary osteoporosis

Osteoporosis is a common disorder, affecting hundreds of millions of people worldwide, and characterized by decreased bone mineral density and increased fracture risk. Known nonheritable risk factors for primary osteoporosis include advanced age, sex-steroid deficiency and increased oxidative stress. Age is a nonmodifiable risk factor, but the influence of a person's lifestyle (diet and physical activity) on their bone structure and density is modifiable to some extent. Heritable factors influencing bone fragility can be monogenic or polygenic. Osteogenesis imperfecta, juvenile osteoporosis and syndromes of decreased bone density are discussed as examples of monogenic disorders associated with bone fragility. So far, the factors associated with polygenic osteoporosis have been investigated mainly in genome-wide association studies. However, epigenetic mechanisms also contribute to the heritability of polygenic osteoporosis. Identification of these heritable and nonheritable risk factors has already led to the discovery of therapeutic targets for osteoporosis, which emphasizes the importance of research into the pathogenetic mechanisms of osteoporosis. Accordingly, this article discusses the many heritable and nonheritable factors that contribute to the pathogenesis of primary osteoporosis. Although osteoporosis can also develop secondary to many other diseases or their treatment, a discussion of the factors that contribute only to secondary osteoporosis is beyond the scope of this Review.

Dietary acid load, kidney function, osteoporosis, and risk of fractures in elderly men and women

SUMMARY

Because kidney dysfunction reduces the ability to excrete dietary acid excess, we hypothesized that underlying kidney function may have confounded the mixed studies linking dietary acid load with the risk of osteoporosis and fractures in the community. In a relatively large survey of elderly men and women, we report that dietary acid load did neither associate with DEXA-estimated bone mineral density nor with fracture risk. Underlying kidney function did not modify these null findings. Our results do not support the dietary acid-base hypothesis of bone loss.

INTRODUCTION

Impaired renal function reduces the ability to excrete dietary acid excess. We here investigate the association between dietary acid load and bone mineral density (BMD), osteoporosis, and fracture risk by renal function status.

METHODS

An observational study was conducted in 861 community-dwelling 70-year-old men and women (49% men) with complete dietary data from the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS). The exposure was dietary acid load as estimated from 7-day food records by the net endogenous acid production (NEAP) and potential renal acid load (PRAL) algorithms. Renal function assessed by cystatin C estimated glomerular filtration rate was reduced in 21% of the individuals. Study outcomes were BMD and osteoporosis state (assessed by DEXA) and time to fracture (median follow-up of 9.2 years).

RESULTS

In cross-section, dietary acid load had no significant associations with BMD or with the diagnosis of osteoporosis. During follow-up, 131 fractures were validated. Neither NEAP (adjusted hazard ratios (HR) (95% confidence interval (CI)), 1.01 (0.85-1.21), per 1 SD increment) nor PRAL (adjusted HR (95% CI), 1.07 (0.88-1.30), per 1 SD increment) associated with fracture risk. Further multivariate adjustment for kidney function or stratification by the presence of kidney disease did not modify these null associations.

CONCLUSIONS

The hypothesis that dietary acid load associates with reduced BMD or increased fracture risk was not supported by this study in community-dwelling elderly individuals. Renal function did not influence on this null finding.

Dairy in adulthood: from foods to nutrient interactions on bone and skeletal muscle health

The risk of fragility fractures exponentially increases with aging. Reduced mass and strength of both bone in osteoporosis and skeletal muscle in sarcopenia play a key role in the age-related incidence of fragility fractures. Undernutrition is often observed in the elderly, particularly in those subjects experiencing osteoporotic fractures, more likely as a cause than a consequence. Calcium (Ca), inorganic phosphate (Pi), vitamin D, and protein are nutrients that impact bone and skeletal muscle integrity. Deficiency in the supply of these nutrients increases with aging. Dairy foods are rich in Ca, Pi, and proteins and in many countries are fortified with vitamin D. Dairy foods are important souces of these nutrients and go a long way to meeting the recommendations, which increase with aging. This review emphaszes the interactions between these 4 nutrients, which, along with physical activity, act through cellular and physiological pathways favoring the maintenance of both bone and skeletal muscle structure and function.