Estimated net endogenous acid production and risk of prevalent and incident hypertension in community-dwelling older people

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.

Chronic Sub-Clinical Systemic Metabolic Acidosis - A Review with Implications for Clinical Practice

When arterial serum pH remains near the lower pH limit of 7.35 for protracted periods of time, a low-grade, sub-clinical form of acidosis results, referred to in this review as chronic, sub-clinical, systemic metabolic acidosis (CSSMA). This narrative review explores the scientific basis for CSSMA, its consequences for health, and potential therapeutic interventions. The major etiology of CSSMA is the shift away from the ancestral, alkaline diet which was rich in fruit and vegetables, toward the contemporary, acidogenic 'Westernized' diet characterized by higher animal protein consumption and lack of base forming minerals. Urine pH is reduced with high dietary acid load and may be a convenient marker of CSSMA. Evidence suggests further that CSSMA negatively influences cortisol levels potentially contributing significantly to the pathophysiology thereof. Both CSSMA and high dietary acid load are associated with the risk and prognosis of various chronic diseases. Clinical trials show that CSSMA can be addressed successfully through alkalizing the diet by increasing fruit and vegetable intake and/or supplementing with alkaline minerals. This review confirms the existence of a significant body of evidence regarding this low-grade form of acidosis as well as evidence to support its diverse negative implications for health, and concludes that CSSMA is a condition warranting further research.

Association between dietary acid load and the risk of hypertension among adults from South China: result from nutrition and health survey (2015-2017)

Background

Higher dietary acid load (DAL) was considered to be associated with an elevated risk of hypertension, while related data from mainland China remains scarce and incomplete. We aim to evaluate the association between DAL and the risk of hypertension among adults from South China.

Methods

We conducted a nutrition and health survey in Guangdong Province located in southern China from 2015 to 2017. A four-stage probability sampling method was utilized to select representative samples of citizens aged ≥18 years old. DAL was assessed by potential renal acid load (PRAL) and net endogenous acid production (NEAP). Participants were divided to 4 groups (Q1-Q4) according to the quartile points of PRAL or NEAP distributions. Generalized linear mixed effects models were applied to evaluate the association between DAL and the risk of hypertension.

Results

A total of 3501 individuals were eligible for this study and 45.9% was male participants. Hypertension rate was 30.7%. A higher PRAL was associated with higher prevalence rate of hypertension among the male (P-trend = 0.03). OR for Q2 was 1.34 (95%CI, 0.94–1.91), Q3 was 1.53 (95%CI = 1.08, 2.16) and Q4 was 1.51 (95%CI, 1.08–2.16) among the male. However, as for total participants, the female, the participants with ≤55 years or participants with > 55 years, the associations were lack of significance. With respect to association between NEAP and hypertension, non-significant results were identified.

Conclusions

The current study indicated male hypertension was associated with higher PRAL, while given to this study was cross-sectional design, further studies are warranted to verify the association.

Dietary acid load and risk of hypertension: A systematic review and dose-response meta-analysis of observational studies

BACKGROUND AND AIM

Previous studies have assessed diet-induced mild metabolic acidosis in relation to blood pressure, however, data are conflicting. Current systematic review and dose-response meta-analysis aimed to summarize earlier findings from observational studies on the association between dietary acid load and hypertension.

METHODS AND RESULTS

We searched the online databases for relevant publications up to Feb 2019, using relevant keywords. Overall, 14 studies (3 prospective and 11 cross-sectional studies) that included 306,183 individuals and 62,264 cases of hypertension were included in the current meta-analysis. Combining effect sizes from both prospective and cross-sectional studies revealed no significant non-linear association between dietary acid load (based on net endogenous acid production (NEAP) method) and hypertension. However, stratified analysis based on study design showed a significant non-linear association between dietary acid load and hypertension in prospective studies (P = 0.006), but not cross-sectional ones. According to linear dose-response analysis, no significant association was found between dietary acid load (based on NEAP) and hypertension (combined effect size: 1.01, 95% CI: 0.97-1.06, P = 0.51). In terms of dietary acid load based on potential renal acid load (PRAL) method, no significant non-linear association was seen with hypertension (P = 0.52). However, in linear dose-response analysis, a-20 unit increase in PRAL values was associated with 3% increased risk of hypertension (combined effect size: 1.03, 95% CI: 1.00-1.06, P = 0.03).

CONCLUSION

We found a significant positive association between dietary acid load and hypertension. Further studies, particularly those with prospective nature, are needed to confirm our findings.

Elevated hypertension risk associated with higher dietary acid load: A systematic review and meta-analysis

BACKGROUND & AIMS

The association between dietary acid load and hypertension risk is inconclusive. We conducted a systematic review and meta-analysis to summarize effect of dietary acid load on blood pressure.

METHODS

A comprehensively search was performed in electronic databases including EMBASE, PubMed, Web of Science and Chinese National Knowledge Infrastructure. Summary ORs and their corresponding 95% CIs were computed assuming a randomized model or fixed model.

RESULTS

Ten publications comprising 4 cohort and 6 cross-sectional studies were eligible for meta-analysis. There were 8 studies about potential renal acid load (PRAL) and 4 about net endogenous acid production (NEAP). Essential hypertension was statistically associated with higher PRAL (OR = 1.14, 95% CI = 1.02-1.17). Our findings also demonstrated a positive impact of higher PRAL on elevating both diastolic pressure (WMD = 0.96, 95% CI = 0.67-1.26) and systolic pressure (WMD = 1.57, 95% CI = 1.12-2.03). A 35% increased risk of hypertension associated with higher NEAP was identified (OR = 1.35, 95% CI = 1.03-1.78).

CONCLUSIONS

The current study suggests that dietary acid load might be potential risk factor of hypertension.

High Protein Intake Is Associated with Lower Risk of All-Cause Mortality in Community-Dwelling Chinese Older Men and Women

OBJECTIVES

To examine the association of the quantity and the source of protein intake with mortality risk in Chinese older adults.

DESIGN

Prospective cohort study.

SETTING

Community.

PARTICIPANTS

Community-dwelling Chinese adults aged >=65 (1,480 men, 1,540 women) in Hong Kong.

MEASUREMENTS

Food frequency questionnaire was used to capture baseline dietary intakes including protein, fiber, total grains, vegetables and fruit intakes. Primary outcome measures, identified from the death registry, were death from all causes, cancer and cardiovascular disease (CVD). Other demographic and lifestyle risk factors were also collected. Multivariate Cox proportion hazards regression was used to examine the association of protein intake with mortality risk.

RESULTS

During a median of 13.8 follow-up years, 963 all-cause deaths, 336 cancer deaths, and 205 CVD deaths were identified. Among men in the highest quintile of total protein intake, all-cause mortality and cancer mortality decreased by 29% [95% confidence interval (CI): 0.55-0.92, p-trend=0.017] and 38% [95% CI: 0.39-0.97, p-trend=0.041] respectively compared with men in the lowest quintile after adjustment for demographics, lifestyle factors and medical conditions. Men in the highest quintile of animal protein intake showed 20% reduced risk of all-cause mortality than men in the lowest quintile (p-trend=0.042). Women in the highest quintile of plant protein intake showed 39% decreased risk of all-cause mortality [95% CI: 0.44-0.85, p-trend=0.019] than those in the lowest quintile. In women, protein intake was not associated with cancer mortality. In both men and women, protein intake was not associated with CVD morality. Further adjustment for other dietary variables attenuated the significant associations.

CONCLUSIONS

Contrary to findings from Caucasian populations of all ages, among Chinese older adults, higher total protein intake was associated with lower all-cause and cancer mortality in Chinese older men. While higher animal protein intake was associated with reduced all-cause mortality in Chinese older men, higher plant protein intake was protective against all-cause mortality in Chinese women. The attenuated associations between protein intake and mortality risk after adjustment for other dietary variables also highlight the role of whole diet approach in mortality risk reduction among older adults.

Higher dietary acid load is weakly associated with higher adiposity measures and blood pressure in Japanese adults: The National Health and Nutrition Survey

Epidemiologic evidence on the associations between dietary acid load and metabolic risk factors are limited and inconsistent. We investigated the hypothesis that dietary acid load is associated with adverse profiles of metabolic risk factors in Japanese adults. This cross-sectional study included 15 618 Japanese adults aged ≥20 years from the 2012 National Health and Nutrition Survey, Japan. Dietary acid load was characterized as potential renal acid load (PRAL) and net endogenous acid production (NEAP) based on information on nutrient intake, which was derived from a 1-day semi-weighed dietary record. After adjustment for potential confounding factors, both PRAL and NEAP were positively associated with body mass index (BMI) and waist circumference in both sexes (P for trend ≤.01). PRAL and NEAP also showed positive associations with systolic and diastolic blood pressure in men, independently of BMI (P for trend ≤.005), while they showed positive associations with systolic (but not diastolic) blood pressure in women (P for trend ≤.03). For other metabolic risk factors, there were positive associations between PRAL and NEAP and total and LDL-cholesterol concentrations only in men (P for trend ≤.04). After excluding participants taking medication for hypertension, dyslipidemia, and diabetes, similar associations were observed for adiposity measures and blood pressure (P for trend ≤.01), with there being positive associations between NEAP and HDL-cholesterol and between PRAL and NEAP and glycated hemoglobin in men (P for trend ≤.04). In conclusion, higher dietary acid load was significantly but weakly associated with higher adiposity measures and blood pressure in Japanese adults.