U-Shaped Association between Dietary Acid Load and Risk of Osteoporotic Fractures in 2 Populations at High Cardiovascular Risk

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.

Dietary Acid Load and Human Health: A Systematic Review and Meta-analysis of Observational Studies

CONTEXT

Dietary acid load (DAL) plays an important role in different aspects of human health.

OBJECTIVE

The aim of this meta-analysis was to systematically synthesize the observational evidence reporting on the associations between the DAL (represented by a potential renal acid load [PRAL] and net endogenous acid production [NEAP]) and a range of health outcomes.

DATA SOURCES

A systematic search of Medline (via PubMed), EMBASE, Scopus, and Web of Science was performed to identify eligible studies.

DATA EXTRACTION

Study screening and risk-of-bias assessment were conducted by 2 independent reviewers.

DATA ANALYSIS

The credibility of each outcome was graded based on predefined criteria: pooled effect size with corresponding 95% CI, 95% prediction interval, heterogeneity, small-study effect, and excess significance bias. In total, 118 observational studies (case-control [n = 22], cross-sectional [n = 65], and cohort [n = 31]) on 38 outcomes were included, incorporating a total population of 1 014 081 participants. Overall, 21/37 and 20/38 of the outcomes reported statistically significant effect sizes for PRAL and NEAP, respectively. The credibility of the evidence for PRAL was rated convincing (class I) for type 2 diabetes (T2D), and as highly suggestive evidence (class II) for overall cancer and systolic blood pressure. By assessing the credibility of the evidence for NEAP, T2D and overall cancer presented convincing evidence (class I) and breast cancer presented highly suggestive evidence (class II). The remaining outcomes presented class III (suggestive) or lower evidence (weak or no association).

CONCLUSION

The higher acid-forming potential of diet was associated with a higher risk of T2D and overall cancer. Since this meta-analysis included observational studies and some of the associations were graded as weak, caution should be exercised in interpreting these associations. Further cohort studies are required with consideration of other factors that can cause biases.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42022336050.

Nutrition and Osteoporosis Prevention

PURPOSE OF REVIEW

Osteoporosis affects 50% of women and 20% of men after the age of 50. Fractures are associated with significant morbidity, increased mortality and altered quality of life. Lifestyle measures for fragility fracture prevention include good nutrition including adequate protein and calcium intakes, vitamin D sufficiency, and regular weight bearing physical exercise.

RECENT FINDINGS

Dietary protein is one of the most important nutritional considerations as it affects bone mineral density, trabecular and cortical microstructure, and bone strength. When calcium intake is sufficient, higher dietary protein intake is associated with lower risk of fracture. Dairy products are a valuable source of calcium and high quality protein. Dairy product consumption, particularly fermented dairy products, are associated with a lower risk of hip fracture and vegan diets are associated with increased fracture risk. Other dietary factors associated with reduced fracture risk include at least 5 servings per day of fruits and vegetables, regular tea drinking, adherence to a Mediterranean diet and other dietary patterns which provide fibers, polyphenols and fermented dairy products. Such dietary patterns may confer health benefits through their effect on gut microbiota composition and/or function. A balanced diet including minerals, protein, fruits and vegetables is an important element in the prevention of osteoporosis and of fragility fracture.

Risk Factors for a Higher Dietary Acid Load (Potential Renal Acid Load) in Free-Living Elderly in Poland

BACKGROUND

Dietary composition is one of the factors influencing the acid-base balance of the body by providing acid or base precursors. One of the methods for assessing the acid-forming potential of a diet is to calculate its potential renal acid load (PRAL). The aim of this study was to identify the sociodemographic, lifestyle, and health factors related to the PRAL.

METHODS

Dietary intake was assessed among 133 individuals aged 70+ years using the three-day record method.

RESULTS

The average PRAL value was 15.7 mEq/day (range from -42.4 to +101.7). The diets of a majority of the participants (71.4%) had acid-forming potential (PRAL > 0). From a univariate analysis, the acid-forming potential of the diets was linked mainly to women (65.3% in PRAL > 0 group vs. 10.5% in PRAL < 0 group), people using dietary supplements, those who consumed alcohol, those who assessed their health as being at least good, people with osteoporosis, those hospitalized during the previous year, and those with rather lower physical activity.

CONCLUSIONS

From a multivariate analysis, gender was the strongest predictor of an acid-forming diet, but the following also contributed: an average self-rated health status (compared to good), a good health status (compared to poor), alcohol drinking, hospitalization, lack of nutritional knowledge, and, to a lesser extent, non-frail status (compared to pre-frail). Therefore, more extensive nutritional education in the identified groups is required.

Dietary acid load and cirrhosis-related mortality: a prospective cohort study

As a global health concern, cirrhosis contributes significantly to morbidity and mortality. This prospective cohort study aimed to investigate the association between dietary acid load (DAL) and cirrhosis-related mortality. Present study was conducted on 121 patients with newly diagnosed cirrhosis who were followed up for 48 months. Anthropometric measures, nutritional status and dietary intakes were assessed and DAL was estimated based on potential renal acid load (PRAL) and net endogenous acid production (NEAP) scores. Crude and multivariable-adjusted hazard ratios (HR) with 95% confidence intervals (CI) were estimated using Cox proportional hazard analyses. Participants in the high PRAL and NEAP scores had significantly higher intakes of grains and lower intakes of fruits and vegetables. Also, the intake of dairy products and legumes, nuts and seeds decreased significantly with increasing NEAP score. After adjustment of all the confounders, the risk of mortality in the second and third tertiles of PRAL was 5.9 times and 10.97 higher than those in the first tertile, respectively (P trend: 0.006). Similarly, comparing the risk of mortality in the second and third tertiles with the first tertile of NEAP showed a 4.46-fold and 12.3-fold increased risk, respectively (P trend: 0.010). Our findings suggested that DAL was significantly associated with cirrhosis-related mortality and highlight the need for further research to understand the underlying mechanisms and establish optimal DAL levels in cirrhotic patients.

Dietary acid load is associated with primary osteoporosis in postmenopausal women aged 50-65 years: A cross-sectional study

This study aimed to investigate the association between dietary acid load (DAL) and primary osteoporosis. This was a cross-sectional study. Among 850 randomly selected postmenopausal women aged 50-65 years, 232 women consisted of 124 women with normal bone mineral density (BMD) and 108 with primary osteoporosis were selected after examining the eligibility criteria. Demographic characteristics, anthropometric indices, and physical activity were collected through questionnaires. Osteoporosis was diagnosed using the dual-energy X-ray absorptiometry method. DAL was assessed by a valid and reliable semiquantitative food frequency questionnaire during the last year. Independent t-test, Mann-Whitney, Chi-square, and adjusted binary logistic regression were used for data analysis through SPSS/24. There were significant differences between the two groups in terms of age, body mass index (BMI), number of deliveries, and years after menopause (p < .05). The mean (standard deviation (SD)) potential renal acid load (PRAL) and net endogenous acid production (NEAP) were higher in postmenopausal women with osteoporosis than those with normal BMD (PRAL: -13.1 ± 11.1 mEq/day vs. -10.8 ± 12.7 mEq/day; NEAP: 29.5 ± 8.5 mEq/day vs. 31.2 ± 9.2 mEq/day). The mean consumption of potassium, magnesium, and calcium in the osteoporosis group was significantly lower than in the other group (p < .05). There were significant associations between osteoporosis with PRAL (odds ratio (OR) = 1.030; 95% confidence interval (CI): 1.001 to 1.060, p = .027) and NEAP scores (OR = 1.041; 95% CI: 1.003 to 1.081, p = .037). The odds of osteoporosis increased by 3% following one unit increase in PRAL score. Similarly, it increased by 4% with increasing NEAP score up to one unit. Therefore, dietary patterns that produce high DAL can have a detrimental effect on bone health.

How Well Do Low-PRAL Diets Fare in Comparison to the 2020-2025 Dietary Guidelines for Americans?

The regular consumption of net acid-producing diets can produce "acid stress" detrimental to human health. Alkalizing diets characterized by a negative potential renal acid load (also called low-PRAL diets (LPD)) enjoy uninterrupted popularity. However, the nutritional adequacy of said diets has rarely been assessed in large populations. Using data from the National Health and Nutrition Examination Surveys, we estimated nutrient intake in individuals consuming an LPD and contrasted the results in an age- and sex-specific manner to individuals on an acidifying diet (high-PRAL diet, HPD). Both groups were compared with the daily nutritional goals (DNG) specified in the 2020-2025 Dietary Guidelines for Americans (DGA). Our analysis included 29,683 individuals, including 7234 participants on an LPD and 22,449 participants on an HPD. Individuals on an LPD numerically met more nutritional goals than individuals on an HPD, yet both failed to meet the goals for several nutrients of public health concern (vitamin D and calcium). As opposed to individuals on an HPD, LPD consumers met the DGA recommendations for saturated fat and potassium. Individuals on an LPD consumed significantly more fiber than individuals on an HPD, as well as yielded a more favorable potassium-to-sodium intake ratio.

Osteoporosis epidemiology using international cohorts

PURPOSE OF REVIEW

To provide an update on the most important new cohort studies within osteoporosis and their bearing on clinical management and directions for future research.

RECENT FINDINGS

We identified a collection of new observational cohort studies - including new reports from already established large cohorts - and intervention studies providing new insights into osteoporosis pathophysiology, risk finding, intervention, and treatment barriers.

SUMMARY

Recent cohort studies in osteoporosis highlight the importance of timely identification and treatment of people who are at high risk of suffering osteoporotic fractures. Physical performance is a strong indicator of fracture risk and one that is tightly linked to a number of chronic conditions, not least inflammatory conditions like rheumatoid arthritis. Advances in case finding may involve opportunistic screening for low bone mineral density and vertebral fractures of radiology images obtained for other purposes, polygenic risk scores, and routinely collected medication and comorbidity information.

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.

Metabolic syndrome and fragility fracture risk

INTRODUCTION

The prevalence of metabolic syndrome has been reported to extremely vary depending on the gender, age, and ethnicity studied. Approximately, 25% of the worldwide adult population is affected by metabolic syndrome, indicating it as a significantly important public health challenge. Likewise, fragility fracture represents an important public health issue too, and the lifetime residual risk of its occurrence has been established in 50% in women and 30% in men over 50 years of age, respectively. Dysmobility syndrome summarizes a cluster of co-existing conditions such as osteoporosis, sarcopenia, obesity. Currently, clinical research focuses essentially on the cardiovascular risks associated with metabolic syndrome. Today, it is conceivable to incorporate all these conditions under a generic "disorder of energy metabolism."

EVIDENCE ACQUISITION

Animal and human studies suggest metabolic and dysmobility syndromes negatively impact on the risk for fragility fracture, contributing to increase the associated mortality rate.

EVIDENCE SYNTHESIS

In recent years, strong correlation between type 2 diabetes, a frequent constitutive part of metabolic syndrome and fragility fracture risk has been reported, but the possible molecular mechanisms by which it can occur are still to be defined.

CONCLUSIONS

Only very few human clinical studies faced these aspects, but they lack adequate endpoints for a good clinical practice in these subjects. Much more still needs to be done before appropriate therapeutic diagnostic pathways will be available for these patients at risk of bone and even generalized fragility. Suggestions for a future overall approach by generating global risk score for these conditions are given.

Nutritional intake and bone health

Osteoporotic or fragility fractures affect one in two women and one in five men who are older than 50. These events are associated with substantial morbidity, increased mortality, and an impaired quality of life. Recommended general measures for fragility fracture prevention include a balanced diet with an optimal protein and calcium intake and vitamin D sufficiency, together with regular weight-bearing physical exercise. In this narrative Review, we discuss the role of nutrients, foods, and dietary patterns in maintaining bone health. Much of this information comes from observational studies. Bone mineral density, microstructure-estimated bone strength, and trabecular and cortical microstructure are positively associated with total protein intake. Several studies indicate that fracture risk might be lower with a higher dietary protein intake, provided that the calcium supply is sufficient. Dairy products are a valuable source of these two nutrients. Hip fracture risk appears to be lower in consumers of dairy products, particularly fermented dairy products. Consuming less than five servings per day of fruit and vegetables is associated with a higher hip fracture risk. Adherence to a Mediterranean diet or to a prudent diet is associated with a lower fracture risk. These various nutrients and dietary patterns influence gut microbiota composition or function, or both. The conclusions of this Review emphasise the importance of a balanced diet including minerals, protein, and fruit and vegetables for bone health and in the prevention of fragility fractures.