Dietary Potential Renal Acid Load Is Positively Associated with Serum Uric Acid and Odds of Hyperuricemia in the German Adult Population

Adequate Vegetable Intake Improves Metabolic Indices in Healthy Japanese Participants: A Randomized Crossover Study

AIM

We aimed to elucidate the effect of a healthy diet containing adequate amounts of protein and vegetables on metabolic indices.

METHODS

In this randomized crossover study, twenty-two healthy Japanese participants ingested two different test meals: fish diet (F) or fish diet with adequate vegetable content (FV). Each 5-day diet load test was separated by a washout period of at least seven days. Metabolic indices were measured in fasting blood and 24-h urine samples.

RESULTS

The delta (Δ) plasma glucose and Δserum low-density lipoprotein (LDL) cholesterol concentrations were significantly larger in the participants in group FV than in group F (p=0.042, p=0.013, respectively). The urinary pH in participants in group F on day 6 was significantly lower than on day 1 (p=0.008), and the Δurinary pH and Δnet gastrointestinal absorption of alkali of participants in group FV tended to be smaller than in group F (p=0.070, p=0.075, respectively).

CONCLUSIONS

This study showed that a healthy diet containing adequate protein and vegetables reduced the dietary acid load and improved plasma glucose and serum LDL concentrations in healthy Japanese participants.

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.

Assessing the role of dietary acid load in the development of hypertensive disorders during pregnancy: uncovering the association through prospective cohort analysis

BACKGROUND

Hypertensive disorders of pregnancy (HDPs) are common complications encountered in pregnancy that affect between 5% and 15% of pregnancies worldwide. Some studies have associated adherence to a diet with a high acid load with an increased risk of HDPs. This study investigates the association between Dietary Acid Load (DAL) and the incidence of preeclampsia, chronic hypertension (HTN), and gestational hypertension (GHTN).

METHODS

Pregnant women aged 18 to 45 in the first trimester of pregnancy were selected and followed up until delivery. Diet was evaluated using a 168-question semi-quantitative food frequency questionnaire (FFQ). After calculating the DAL score, the inverse probability weight of the propensity scores, estimated from augmented generalized models, was used to obtain a causal risk ratio (RR) adjusted for potential confounders.

RESULTS

Out of 1,856 women, 92 (4.95%) developed preeclampsia. The potential renal acid load (PRAL) score ranged from - 16.14 to 0.58, while the net endogenous acid production (NEAP) score ranged from 34.61 to 50.15. Multivariable analysis revealed a significant association between PRAL and preeclampsia in the first (aRR: 1.87, 95% CI: 1.01, 3.49, p = 0.048) and third (aRR: 2.01, 95% CI: 1.07, 3.81, p = 0.030) quartiles compared to the reference group (Q2). No significant linear association was found in continuous analyses. For chronic HTN, significant associations were observed in the first (aRR: 2.56, 95% CI: 1.21, 5.42, p = 0.014) and fourth (aRR: 4.79, 95% CI: 2.37, 9.71, p < 0.001) PRAL quartiles, with similar findings for NEAP. Continuous analysis showed a significant linear association between both PRAL and NEAP scores and chronic HTN. Regarding GHTN, significant associations were found in the first (aRR: 1.48, 95% CI: 1.02, 2.16, p = 0.041) and fourth (aRR: 1.88, 95% CI: 1.31, 2.70, p = 0.001) PRAL quartiles, and in Q4 for NEAP (aRR: 1.56, 95% CI: 1.10, 2.21, p = 0.012), with no significant linear association in continuous analysis.

CONCLUSION

Extremes in DAL, as indicated by PRAL and NEAP, are associated with an increased risk of preeclampsia, chronic HTN, and GHTN, particularly in the highest and lowest quartiles. These findings highlight the potential impact of DAL on HDPs.

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.

A combination of red and processed meat intake and polygenic risk score influences the incidence of hyperuricemia in middle-aged Korean adults

BACKGROUND/OBJECTIVES

The high consumption of purine-rich meat is associated with hyperuricemia. However, there is limited evidence linking the consumption of red and processed meat to the genetic risk of hyperuricemia. We investigated the relationship between various combinations of red and processed meat consumption and the polygenic risk scores (PRSs) and the incidence of hyperuricemia in middle-aged Koreans.

SUBJECTS/METHODS

We analyzed the data from 44,053 participants aged ≥40 years sourced from the Health Examinees (HEXA) cohort of the Korean Genome and Epidemiology Study (KoGES). Information regarding red and processed meat intake was obtained using a semiquantitative food frequency questionnaire (SQ-FFQ). We identified 69 independent single-nucleotide polymorphisms (SNPs) at uric acid-related loci using genome-wide association studies (GWASs) and clumping analyses. The individual PRS, which is the weighted sum of the effect size of each allele at the SNP, was calculated. We used multivariable Cox proportional hazards models adjusted for covariates to determine the relationship between red and processed meat intake and the PRS in the incidence of hyperuricemia.

RESULTS

During an average follow-up period of 5 years, 2,556 patients with hyperuricemia were identified. For both men and women, the group with the highest red and processed meat intake and the highest PRS was positively associated with the development of hyperuricemia when compared with the group with the lowest red and processed meat intake and the lowest PRS (hazard ratio [HR], 2.72; 95% confidence interval [CI], 2.10-3.53; P < 0.0001; HR, 3.28; 95% CI, 2.45-4.40; P < 0.0001).

CONCLUSION

Individuals at a high genetic risk for uric acid levels should moderate their consumption of red and processed meat to prevent hyperuricemia.

Higher dietary acid load is associated with the risk of hyperuricemia

PURPOSE

Dietary acid load plays a key role in regulating serum uric acid levels. We hypothesized that dietary acid load indices would be positively associated with the odds of hyperuricemia. We aimed to test this hypothesis in a representative sample of Iranian adult population.

METHODS

In this cross-sectional study, a total of 6145 participants aged 35-65 years were recruited from MASHAD cohort study. Dietary intakes were assessed using a 24-h dietary recall. Diet-based acid load was assessed as the potential renal acid load (PRAL), net endogenous acid production (NEAP), and dietary acid load (DAL). Hyperuricemia was defined as serum uric acid greater than the 75th percentile. Multivariable logistic regression models were applied to determine the association between diet-based acid load scores and hyperuricemia.

RESULTS

The mean age of participants was 48.89 ± 8.09 years. Overall, 25.7% had hyperuricemia. According to the full-adjusted model, there was a significant association between higher tertile of PRAL, and DAL and hyperuricemia (Q3 PRAL; OR (95% CI): 1.23 (1.05-1.43), Q3 DAL; OR (95% CI): 1.22 (1.05-1.42)). Regarding NEAP, there was no significant association with hyperuricemia. We also found that dietary intake of total sugars, fiber, calcium, and magnesium was associated with the odds of hyperuricemia in our population.

CONCLUSION

This study showed a significant positive association between two indicators of dietary acid load (PRAL, and DAL) and odds of hyperuricemia among Iranian adults.

Dietary acid load decreases with age and is associated with sagittal abdominal diameter: a nationally representative quantification study in US adults

BACKGROUND

Dietary acid load (DAL) has been associated with frailty and hip fractures in older adults, who often have a reduced kidney function and thus compromised buffering capacities. Studies to quantify DAL in older adults are scarce and controversies persist as to whether DAL in- or decreases with age.

AIM

To enhance the understanding of DAL in older individuals, we examined its relationship with increasing age and selected anthropometric data in a well-characterized sample of US adults.

METHODS

Secondary data analysis of nationally representative data from the National Health and Nutrition Examination Surveys data (NHANES 2011-2016). The sample included n = 3018 adults aged 60+, which may be extrapolated to represent n = 45,113,471 Americans. DAL was estimated using 4 formulas, including Potential Renal Acid Load (PRAL) and Net Endogenous Acid Production (NEAP).

RESULTS

All employed DAL scores tended to decline with increasing age. Participants aged 80 years or older yielded the lowest DAL scores. The average US citizen aged 60+ consumed an acidifying diet, yet there were sex-specific differences in the adjusted means for some scores. NEAP was positively correlated with both body mass index (r = 0.26, p < 0.001) and the sagittal abdominal diameter (r = 0.31, p < 0.001) in this nationally representative sample.

CONCLUSION

The previously reported phenomenon of increasing DAL values in older people in non-Western countries may not apply to the US. Our findings may constitute an important step towards a better understanding of DAL in older US adults, and highlight the need for additional population-specific research in the field.

Association between dietary acid load and the odds of ulcerative colitis: a case-control study

Ulcerative colitis (UC) is one of the two types of inflammatory bowel disease (IBDs), which have a pivotal role in weakening the quality of lives of suffering patients. According to some recent studies, significant changes in dietary patterns may have contributed to the increased prevalence of UC. Potential renal acid load (PRAL) is an index used to estimate dietary acid load of the diet. The aim of the current study is to investigate the association between PRAL and odds of UC. The current case-control study included 62 newly diagnosed cases of UC and 124 healthy controls. Dietary habits of participants in the last year were collected with a valid food frequency questionnaire (FFQ). Thereafter, PRAL score was calculated based on a formula containing the dietary intake of protein, phosphorus, potassium, calcium, and magnesium. Participants were categorized according to quartiles of PRAL. Multivariable logistic regression models were used to estimate the odds' ratio (OR) with 95% confidence intervals (CIs) of UC across quartiles of PRAL. The results of the current study indicated that in the crude model, participants in the fourth quartile of PRAL had 2.51 time higher odds of UC compared with those in the first quartile of the PRAL [(OR 2.51; 95% CI 1.03-6.14), (P = 0.043)]. After adjustment for age and biological gender, this positive association remained significant [(OR 2.99; 95% CI 1.16-7.72), (P = 0.023)]. In the final model, after further adjustment for BMI, current smoking, education, Helicobacter pylori infection, and dietary intakes of total energy, omega-3 fatty acids, trans-fatty acids, and total dietary fiber, the odds of UC in the highest quartile of PRAL was significantly higher compared to the lowest quartile [(OR 3.08; 95% CI 1.01-9.39), (P = 0.048)]. So, we observed that higher dietary acid load assessed by PRAL score is associated with greater odds of UC.

Protein intake and risk of urolithiasis and kidney diseases: an umbrella review of systematic reviews for the evidence-based guideline of the German Nutrition Society

PURPOSE

Changes in dietary protein intake metabolically affect kidney functions. However, knowledge on potential adverse consequences of long-term higher protein intake (HPI) for kidney health is lacking. To summarise and evaluate the available evidence for a relation between HPI and kidney diseases, an umbrella review of systematic reviews (SR) was conducted.

METHODS

PubMed, Embase and Cochrane Database of SRs published until 12/2022 were searched for the respective SRs with and without meta-analyses (MA) of randomised controlled trials or cohort studies. For assessments of methodological quality and of outcome-specific certainty of evidence, a modified version of AMSTAR 2 and the NutriGrade scoring tool were used, respectively. The overall certainty of evidence was assessed according to predefined criteria.

RESULTS

Six SRs with MA and three SRs without MA on various kidney-related outcomes were identified. Outcomes were chronic kidney disease, kidney stones and kidney function-related parameters: albuminuria, glomerular filtration rate, serum urea, urinary pH and urinary calcium excretion. Overall certainty of evidence was graded as 'possible' for stone risk not to be associated with HPI and albuminuria not to be elevated through HPI (above recommendations (> 0.8 g/kg body weight/day)) and graded as 'probable' or 'possible' for most other kidney function-related parameters to be physiologically increased with HPI.

CONCLUSION

Changes of the assessed outcomes may have reflected mostly physiological (regulatory), but not pathometabolic responses to higher protein loads. For none of the outcomes, evidence was found that HPI does specifically trigger kidney stones or diseases. However, for potential recommendations long-term data, also over decades, are required.

The Impact of Plant-Based Diets on Dietary Acid Load Metrics in Venezuela: A Cross-Sectional Study

Dietary acid load (DAL) is an important determinant of the acid-base balance in humans and has been associated with several chronic non-communicable diseases. Plant-based diets, including vegetarian and vegan diets, decrease DAL-although their alkalizing potential varies substantially. Their net effect on common DAL scores, including potential renal acid load and net endogenous acid production, has been insufficiently quantified and is poorly understood-particularly in populations outside of Europe and North America. We assessed the associations between three plant-based dietary patterns (flexitarian vs. lacto-ovo-vegetarian vs. vegan diet) and DAL scores in a healthy Venezuelan population in the metropolitan area of Puerto La Cruz, Venezuela. Substantial differences in DAL scores were observed, whereby the vegan diet yielded the highest alkalizing potential, followed by the lacto-ovo-vegetarian and the flexitarian diet. DAL scores were substantially lower in comparison to European and North American plant-based populations, probably due to the higher potassium intake (exceeding 4000 mg/d in vegans), the higher magnesium intake (390.31 ± 1.79 mg/d in vegans) and the lower intake of protein in vegans and lacto-ovo-vegetarians. Additional studies in other non-industrialized populations are warranted to allow for a better understanding of the (numeric) impact of plant-based dietary patterns on DAL scores, potentially allowing for an establishment of reference ranges in the near future.

Association between Dietary Acid Load and Hyperuricemia in Chinese Adults: Analysis of the China Health and Nutrition Survey (2009)

BACKGROUND

This study evaluates the association between dietary acid load (DAL) and hyperuricemia in Chinese adults.

METHODS

The China Health and Nutrition Survey (CHNS) in 2009 was used in this cross-sectional study. Potential renal acid load (PRAL) and net endogenous acid production (NEAP) were applied to estimate DAL. A multiple logistic regression model was used to test the relationship between DAL and hyperuricemia risk.

RESULTS

A total of 7947 participants were included in this study, of whom 1172 had hyperuricemia. The PRAL score was positively related to the prevalence of hyperuricemia, even when potential covariates were taken into account. In comparison with Q1, the ORs were 1.12 (95% CI, 0.92-1.38), 1.20 (95% CI, 0.97-1.47) and 1.42 (95% CI, 1.16-1.75) in Q2, Q3 and Q4. However, there was no significant relationship between NEAP scores and hyperuricemia. Every 10 g increase in energy-adjusted fat, protein and animal protein intakes caused a 10%, 17% and 18% increase in hyperuricemia risk, respectively (OR: 1.10, 95% CI: 1.04-1.16; OR: 1.17, 95% CI: 1.11-1.25; OR: 1.18, 95% CI: 1.12-1.24, respectively). An obvious linear correlation was also suggested by the restricted cubic spline.

CONCLUSIONS

Hyperuricemia risk was associated with higher PRAL among Chinese adults. This means that a diet low in PRAL scores could be a very valuable uric acid-lowering dietary pattern.

Purine Content and Renal Acid Load Evaluation in Healthy Japanese Diets

During the treatment of hyperuricemia, attention should be paid to purine intake as part of the diet. Additionally, many patients with obese hyperuricemic expect early weight loss through glucose restriction. However, the amounts of purine in the diet are unknown. This study aimed to compare the purine content and potential renal acid load (PRAL) of a hospital diet and a low carbohydrate (LC). We calculated the nutritional values in the menus of the normal hospital (NH), energy-control (EC) diets served at several Shizuoka general hospitals, and the menus of LC diets. The amount of purine and PRAL was determined based on the nutritional values. The average daily purine content and energy were NH 349.0 mg, 1,808 kcal, EC 340.4 mg, 1,681 kcal, and LC 697.6 mg, 1,454 kcal, respectively. LC consumed more purine than the recommended daily intake of 400 mg. The PRAL score for NH was 4.5 mEq/d, EC 3.8 mEq/d, and LC 19.0 mEq/d, with LC representing diets with a higher acid load. In terms of both purine intake and uric acid excretion, the hospital diet is preferred over the low-carbohydrate diet for patients. Dietitians should exercise caution when recommending a low-carbohydrate diet for patients with hyperuricemia.

Nutrient scoring for the DEGS1-FFQ - from food intake to nutrient intake

BACKGROUND

While necessary for studying dietary decision-making or public health, estimates of nutrient supply based on self-reported food intake are barely accessible or fully lacking and remain a challenge in human research. In particular, detailed information on dietary fiber is limited. In this study we introduce an automated openly available approach to assess self-reported nutrient intake for research purposes for a popular, validated German food frequency questionnaire (FFQ).

METHODS

To this end, we i) developed and shared a code for assessing nutrients (carbohydrates, fat, protein, sugar, fiber, etc.) for 53 items of the quantitative, validated German DEGS1-FFQ questionnaire implementing expert-guided nutritional values of diverse sources with several raters. In a sample of individuals (nGUT-BRAIN = 61 (21 female) overweight, omnivorous), we ii) cross-validated nutrient intake of the last 7 days and the last 24 h and iii) computed test-retest reliability across two timepoints. Further, iv) we reported newly computed nutrient intake for two independent cross-sectional cohorts with continuous weight status and different dietary habits (nMensa = 134 (79 female, 1 diverse), nGREADT = 76 male). Exploratively, we v) correlated computed, energy-adjusted nutrient intake with anthropometric markers and HbA1c and vi) used linear mixed models to analyse the predictability of BMI and WHR by nutrient intake.

RESULTS

In overweight adults (n = 61 (21 female), mean age 28.2 ± 6.5 years, BMI 27.4 ± 1.6 kg/m2) nutrient intakes were mostly within recommended reference nutrient ranges for both last 7 days and last 24 h. Recommended fiber intake was not reached and sugar intake was surpassed. Calculated energy intake was significantly higher from last 24 h than from last 7 days but energy-adjusted nutrient intakes did not differ between those timeframes. Reliability of nutrient values between last 7 days and 24 h per visit was moderate (Pearson's rhoall ≥ 0.33, rhomax = 0.62) and absolute agreement across two timepoints was low to high for 7 days (Pearson's rhomin = 0.12, rhomax = 0.64,) and low to moderate for 24 h (Pearson's rhomin = 0.11, rhomax = 0.45). Associations of dietary components to anthropometric markers showed distinct sex differences, with overall higher intake by males compared to females and only females presenting a negative association of BMI with fiber intake. Lastly, in the overweight sample (but not when extending the analysis to a wider BMI range of 18.6-36.4 kg/m2), we could confirm that higher BMI was predicted by lower energy-adjusted fiber intake and higher energy-adjusted fat intake (when adjusting for age, sex and physical activity) while higher WHR was predicted by higher energy intake.

CONCLUSION

We provide an openly available tool to systematically assess nutrient intake, including fiber, based on self-report by a common German FFQ. The computed nutrient scores resembled overall plausible and reliable measures of nutrient intake given the known limitations of FFQs regarding over- or underreporting and suggest valid comparability when adjusting for energy intake. Our open code nutrient scoring can help to examine dietary intake in experimental studies, including dietary fiber, and can be readily adapted to other FFQs. Further validation of computed nutrients with biomarkers and nutrient-specific metabolites in serum, urine or feces will help to interpret self-reported dietary intake.

Higher dietary acid load is associated with hyperuricemia in Chinese adults: a case-control study

BACKGROUND

This study aims to explore the association between dietary acid load and hyperuricemia in Chinese adults.

METHODS

A case-control study was conducted. Adult participants with hyperuricemia were recruited as the cases and those without hyperuricemia were as the controls. Food consumption was evaluated by food frequency questionnaire (FFQ). Dietary acid load was assessed by potential renal acid load (PRAL) and net endogenous acid production (NEAP). Dietary acid load was divided into four levels: the first quartile (Q1), the second quartile (Q2), the third quartile (Q3) and the fourth quartile (Q4). Logistic regression model was applied for exploring the association between dietary acid load (PRAL and NEAP) and hyperuricemia. Odds ratio (OR) and its correspondence confidence interval (CI) were computed.

RESULTS

A total of 290 participants were eligible in this study, in which there were 143 individuals in case group and 147 in control group. A higher level of PRAL was found to be associated with odds of hyperuricemia. ORs of hyperuricemia for Q2, Q3 and Q4 of PRAL were 2.74 (95%CI: 1.94 ~ 3.88, p-value: 0.004), 2.90 (95%CI: 2.05 ~ 4.10, p-value: 0.002) and 3.14 (95%CI: 2.22 ~ 4.45, p-value: 0.001), respectively. There was a positive association between elevated NEAP and hyperuricemia. OR of hyperuricemia for Q2 was not material significance (OR:1.54, 95%CI: 0.93 ~ 2.53, p-value: 0.210), however, ORs of hyperuricemia for Q3 (OR: 2.40, 95%CI: 1.70 ~ 3.38, p-value: 0.011) and Q4 (OR: 3.27, 95%CI: 2.31 ~ 4.62, p-value: 0.001) were statistically significant.

CONCLUSION

Higher level of dietary acid load was found to be associated with hyperuricemia in Chinese adults, indicative of advocation of a well-balanced diet in this population.

Observational and clinical evidence that plant-based nutrition reduces dietary acid load

Contemporary diets in Western countries are largely acid-inducing and deficient in potassium alkali salts, resulting in low-grade metabolic acidosis. The chronic consumption of acidogenic diets abundant in animal-based foods (meats, dairy, cheese and eggs) poses a substantial challenge to the human body's buffering capacities and chronic retention of acid wherein the progressive loss of bicarbonate stores can cause cellular and tissue damage. An elevated dietary acid load (DAL) has been associated with systemic inflammation and other adverse metabolic conditions. In this narrative review, we examine DAL quantification methods and index observational and clinical evidence on the role of plant-based diets, chiefly vegetarian and vegan, in reducing DAL. Quantitation of protein and amino acid composition and of intake of alkalising organic potassium salts and magnesium show that plant-based diets are most effective at reducing DAL. Results from clinical studies and recommendations in the form of expert committee opinions suggest that for a number of common illnesses, wherein metabolic acidosis is a contributing factor, the regular inclusion of plant-based foods offers measurable benefits for disease prevention and management. Based on available evidence, dietary shifts toward plant-based nutrition effectively reduces dietary-induced, low-grade metabolic acidosis.

Dietary Acid Load Is Positively Associated with the Incidence of Hyperuricemia in Middle-Aged and Older Korean Adults: Findings from the Korean Genome and Epidemiology Study

Hyperuricemia has been associated with a number of chronic diseases, such as type 2 diabetes mellitus, hypertension, and cardiovascular diseases. Dietary acid load plays a key role in regulating uric acid levels. We hypothesized that potential renal acid load (PRAL) and net endogenous acid production (NEAP) score would be positively associated with the incidence of hyperuricemia. Data from the Health Examinees study, a part of the Korean Genome and Epidemiology Study were used. The PRAL and NEAP scores were calculated to evaluate the dietary acid load. Hyperuricemia was defined as follows: >7.0 mg/dL and >6.0 mg/dL of serum uric acid levels in men and women, respectively. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of hyperuricemia. We identified 2500 new cases of hyperuricemia during a mean follow-up of 5.0 years (223,552 person years). The participants in the highest quartiles of the PRAL and NEAP score had 21% (HR: 1.21, 95% CI: 1.07–1.35, p for trend <0.0001) and 17% (HR: 1.17, 95% CI: 1.04–1.31, p for trend <0.0001) higher risks for hyperuricemia, respectively, than those in the lowest quartiles, after adjusting for covariates. In this prospective cohort study, a higher dietary acid load was positively associated with a higher incidence of hyperuricemia in Korean adults. This suggests that an alkaline diet may be an effective strategy to reduce the future risk of elevated uric acid levels.

Gender-Specific Inverse Associations Between Beans Intake, Serum Urate Levels, and Hyperuricemia: A Cross-Sectional Analysis Based on the Henan Rural Cohort Study

Background and Aims: Beans are rich in purines, which are important substances that lead to elevated serum urate, especially exogenous purines. Few studies were conducted to assess the relationship between beans intake and serum urate or hyperuricemia, especially in rural people. The purpose of this study was to validate the association by gender in the rural Chinese population. Methods: A total of 38,855 participants aged 18-79 years old were enrolled from the Henan Rural Cohort Study (Registration number: ChiCTR-OOC-15006699). Dietary data were collected using a validated food frequency questionnaire (FFQ). Linear regression models and logistic regression models were used to examine the associations between beans intake and serum urate levels or hyperuricemia. Restricted cubic spline regression was performed to display the dose-response relationship. Results: In multivariate-adjusted linear regression, an inverse correlation was found between beans intake and serum urate level (the highest quartile Q4 vs. the bottom quartile Q1) in both men (P = 0.008) and women (P < 0.001). Per 10-g increment in beans intake was associated with 0.30 μmol/L decreased concentration of serum urate in men and 0.71 μmol/L in women. The multivariate-adjusted odds ratios (ORs) of hyperuricemia were 0.83 (0.71, 0.97) in men and 0.73 (0.63, 0.84) in women (Q4 vs. Q1). Per 10-g increment in beans intake created a 1% decreased risk of hyperuricemia in men and 3% in women. The cubic spline suggested a risk reduction for hyperuricemia with increasing intake of beans. Conclusion: A higher beans intake was associated with a lower serum urate level and a reduced risk of hyperuricemia in both sexes, and the association was more pronounced in women.

Uric Acid Variability and All-Cause Mortality: A Prospective Cohort Study in Northern China

OBJECTIVES

Uric acid(UA) is related with cardiovascular disease, but the association of UA variability with all-cause mortality is rarely known. This study aimed to investigate the relationship between UA variability and all-cause mortality in Kailuan cohort study in northern China.

DESIGN

Cohort study.

SETTING

Kailuan community hospitals in Tangshan, Hebei province, Northern China.

PARTICIPANTS

A total of 55717 participants from Kailuan Study were enrolled, and our study followed up biennially from 2006 to 2010.

MEASUREMENTS

Clinical records of the participants enrolled were analyzed. UA variation independent of mean (UAVIM) values were calculated and all the participants were quartile grouped into four groups as: Q1(UAVIM<0.68), Q2(0.68≤UAVIM<1.10), Q3(1.10≤UAVIM<1.67) and Q4(UAVIM≥1.67). The endpoint event was all-cause death. Cox regression model was performed to evaluate the hazard ratios(HRs) of all-cause mortality based on UAVIM groups.

RESULTS

During a median follow-up of 6.83 years, 2926 deaths occurred. The accumulated mortality rates were 4.6%, 4.8%, 5.4% and 6.1% in group Q1, Q2, Q3 and Q4 respectively. When adjusted potential confounders, the highest risk for all-cause mortality was in group Q4 and the adjusted HRs and 95% confidence intervals(CIs) of group Q2-Q4 for all-cause death were 1.044(0.937, 1.164), 1.182(1.064, 1.314) and 1.353(1.220, 1.501) compared with group Q1, respectively. Further analysis showed that the risk for all-cause death increased as UAVIM value increased. Sensitive analysis still showed the similar results when excluding participants with hyperuricemia or severe chronic kidney diseases. Sub-group analysis by age, gender, BMI or hypertension history also indicated analogous results.

CONCLUSION

Elevated UAVIM was related with increased all-cause mortality and UAVIM was an independent risk factor for all-cause mortality in the community cohort study.

Estimates of renal net acid excretion and their relationships with serum uric acid and hyperuricemia in a representative German population sample

BACKGROUND/OBJECTIVE

Preliminary interventional data suggest that a reduction of dietary acid load raises renal uric acid excretion and decreases serum uric acid (SUA). In line with this, in a recent cross-sectional analysis of a representative adult population sample, a higher potential renal acid load (PRAL) was found to associate with higher SUA levels. Against this background, we re-examined the relationship of the body's acid load with SUA and hyperuricemia using nutrition-derived estimates of renal net acid excretion (NAE).

SUBJECTS/METHODS

Cross-sectional analyses were performed in n = 6894 participants (18-79 y) of the German Health Interview and Examination Survey for Adults (DEGS1). Two different approaches were used to estimate NAE, one based on the sum of food frequency questionnaire (FFQ)-derived PRAL and body-surface area-derived organic acids (eNAE_PRAL+OA) and the other based on FFQ-derived protein and potassium intake ratios (eNAE_Prot/K). The associations of eNAE_PRAL+OA and eNAE_Prot/K with SUA were analyzed in multiple linear regression models. Multiple logistic regressions were used to calculate odds ratios (OR) for hyperuricemia comparing higher (T3) and lower (T1) tertiles of the NAE estimates.

RESULTS

After adjusting for relevant confounders, eNAE_PRAL+OA (p = 0.0048) and eNAE_Prot/K (p = 0.0023) were positively associated with SUA. In addition, participants with a higher eNAE_PRAL+OA or eNAE_Prot/K had higher ORs for having hyperuricemia (OR: 1.73, 95% CI: 1.24-2.40, OR: 1.51, 95% CI: 1.10-2.08, respectively).

CONCLUSION

The results substantiate findings of a previous analysis that dietary acid load is a potential influencing factor on SUA. This implicates that a lower dietary acid load may have beneficial effects on SUA.

Hyperuricemia versus lifestyle in men and women of the Russian Federation population

Objective ― Analyzing gender-related specificities of hyperuricemia associations with lifestyle choices in the Russian Federation (RF) population. Material and Methods ― Cross-sectional survey was performed within the guidelines of the Russian national multicenter study ESSE-RF. The final sample size was 20781 people 25-64 years old. The effect of age, body mass index (BMI), diet, smoking status, and alcohol consumption on the incidence of hyperuricemia was evaluated. The analysis was carried out separately for men and women, using logistic regression. To build a model for predicting hyperuricemia, classification trees were used. Results ― Multidirectional associations of hyperuricemia were revealed both in women (with BMI, age, ‘Smart’ dietary pattern, alcohol consumption) and in men (with BMI, ‘smart’ dietary pattern, alcohol consumption, smoking status). The predictive accuracy of hyperuricemia incidence models was 60.4% in women vs. 65.7% in men. In both gender groups, BMI had the highest contribution to predicting the hyperuricemia incidence, while the next predictors, in terms of significance, differed among men and women. In women, the greatest impact, in decreasing order, was exerted by age, dietary patterns and drinking, whereas in men, by smoking status, dietary patterns and drinking. Conclusion ― In the RF population, there are multiple gender-specific associations of hyperuricemia with lifestyle choices, particularly nutrition, smoking and alcohol consumption.

Dietary Acid Load: A Novel Nutritional Target in Overweight/Obese Children with Asthma?

Obesity has been repeatedly linked to asthma, and several potential mechanisms have been proposed in the etiologies of the obese-asthma phenotype. Considering that lungs play an important role in systemic pH and acid–base regulation, are a key organ in asthma development, and that nutritional inadequacy of several nutrients and high dietary acid load can affect airway inflammation and reactivity, we aimed to test the hypothesis that dietary acid load may be associated with asthma in children. Data on 699 children (52% females), aged 7–12 years, were analyzed. Anthropometric measurements were performed to assess body mass index. Dietary acid load was calculated using potential renal acid load (PRAL) equations from a 24 h dietary recall administrated to children. Adjusted PRAL for total energy intake was applied with the use of the residual method. Lung function and airway reversibility were assessed with spirometry. Asthma was defined by a positive bronchodilation or self-reported medical diagnosis with reported symptoms (wheezing, dyspnea, or dry cough) in the past 12 months. After adjustment for energy intake, sex, age, parent’s education level, and physical activity, positive and significant associations were found between asthma and PRAL [odds ratio (OR) = 1.953, 95% CI = 1.024, 3.730) in overweight/obese children. Our findings suggest that dietary acid load might be a possible mechanism in overweight/obese-asthma phenotype development.

Dietary acid load, kidney function and risk of chronic kidney disease: A systematic review and meta-analysis of observational studies

Aim: Study findings examining the association between dietary acid load (DAL), kidney function and risk of chronic kidney disease (CKD) are inconsistent and there has been no meta-analysis on the relationship between DAL, kidney function and risk of CKD, hence we investigated this association in this paper. Methods: PubMed, ISI web of science and Scopus were searched up to January 2018 to identify all relevant articles. Effect sizes of eligible studies were pooled in random- effect model using the Der Simonian-Laird method. The I² index was used to assess the amount of heterogeneity. Result: Twenty three studies with 200092 subjects were included. Meta-analysis of 9 observational studies showed that DAL had a positive significant association with risk of CKD (1.31; 95% CI: 1.06, 1.62; P = 0.011). Furthermore, increased DAL can decrease urine pH (-0.47; 95% CI: -0.85, -0.08; P = 0.017) significantly. Subgroup analysis could not identify the sources of heterogeneity about the association of DAL and risk of CKD. However, it showed the method of measurement was the source of heterogeneity about the association of DAL and urine pH (24 h urine pH: -0.62; 95% CI: -0.70, -0.54; P < 0.0001; Fasting urine pH: -0.08; 95% CI: -0.18, 0.02; P = 0.111). Conclusion: Our study showed that DAL can increase the risk of CKD and have an inverse association with urine pH.

Dietary Acid Load: mechanisms and evidence of its health repercussions

Diet composition has long been known to influence acid-base balance by providing acid or base precursors. In general, foods rich in protein, such as meat, cheese, eggs, and others, increase the production of acid in the body, whereas fruit and vegetables increase alkalis. The capacity of acid or base production of any food is called potential renal acid load (PRAL). Diets high in PRAL induce a low-grade metabolic acidosis state, which is associated with the development of metabolic alterations such as insulin resistance, diabetes, hypertension, chronic kidney disease, bone disorders, low muscle mass and other complications. The aim of this paper is to review the available evidence which evaluates the association of the PRAL of the diet with the incidence of chronic diseases and metabolic disorders, as well as related mechanisms involved in their development.