Link Between Dietary Acid Load and Mortality

Introduction to Metabolic Acidosis and Cardiometabolic Conditions

Previous research has established a connection between metabolic acidosis from dietary sources and various cardiometabolic disorders, including hypertension and type 2 diabetes. A recent study further explored the relationship between dietary acid load and all-cause mortality, particularly in a Japanese population.

Influence of Chronic Illnesses on Mortality

Chronic diseases significantly contribute to global mortality rates, many of which stem from modifiable lifestyle choices such as diet. The body’s acid-base balance is influenced by dietary habits; evidence indicates that diet-induced metabolic acidosis correlates with cardiometabolic issues such as hypertension and type 2 diabetes. Consuming a diet high in acidogenic foods—such as meat, fish, and cheese—while low in alkaline options like fruits and vegetables may lead to increased endogenous acid production.

Measuring Dietary Acid Load

Researchers use potential renal acid load (PRAL) and net endogenous acid production (NEAP) scores, derived from dietary intake, to estimate dietary acid load.

Study Overview

The study by Akter and colleagues, published in the American Journal of Clinical Nutrition, investigates the relationship between food consumption, acid production, and total mortality risk. This research is notable as it is the first to assess the association between dietary acid load and total or cause-specific mortality within an Asian demographic.

Cohort Details and Methodology

The Japan Public Health Center-based study began in 1990 and 1993, involving two cohorts. Cohort I included individuals aged 40 to 59 from five public health centers, while Cohort II comprised residents aged 40 to 69 from six other centers. Researchers utilized self-administered questionnaires at baseline and during follow-ups at five and ten years. These surveys collected data on medical histories and lifestyle factors such as smoking, alcohol consumption, and dietary practices.

The five-year follow-up questionnaire provided more reliable food intake data, which was used as a baseline for analysis. The food-frequency questionnaire (FFQ) evaluated the average consumption of 147 food and beverage items over the previous year.

Calculating PRAL and NEAP Scores

PRAL scores were calculated based on the intake of protein, phosphorus, potassium, calcium, and magnesium, while NEAP scores relied on protein and potassium consumption. Negative PRAL scores indicated alkaline diets, whereas positive scores reflected acidic diets.

The initial analysis included 102,366 participants who completed the second FFQ. Exclusions were made for 7,761 participants with a history of cancer, stroke, ischemic heart disease, or chronic liver disease. Additionally, 950 individuals with extreme energy intakes and 1,177 with unusual dietary load scores were also removed, resulting in a final analysis of 92,478 participants.

Findings and Results

The study found that a higher dietary acid load score, determined by PRAL and NEAP, was associated with an increased risk of total mortality, particularly cardiovascular disease (CVD). This association persisted even after adjusting for variables such as BMI, diabetes, hypertension, and dyslipidemia, indicating that the link could not be solely attributed to these conditions. PRAL values were also correlated with cerebrovascular disease, but no significant relationship was found between dietary acid load and cancer mortality.

Study Strengths and Limitations

The authors highlighted several strengths of the study, including a large participant pool, an extended follow-up duration, and the use of a validated FFQ. However, they acknowledged limitations such as the reliance on a single baseline dietary assessment, which may not reflect long-term eating patterns. Additionally, including individuals with prior medical conditions who might have altered their diets based on medical advice could have skewed the results. While the authors excluded these individuals in some calculations, the outcomes remained consistent. The absence of biomarkers to validate PRAL or NEAP scores was also noted as a limitation, along with the potential influence of unmeasured variables.

Furthermore, they considered how the findings might be affected by the specific demographic of middle-aged to older Japanese participants, which may limit generalizability to broader populations.

Conclusion

The study’s results suggest that a high dietary acid load may influence mortality rates within this Asian population. Understanding the impact of acid-base balance on longevity could empower individuals to reduce their risk of death, particularly from CVD, by managing their dietary acid-base intake.

Written By: Sara Alvarado BSc, MPH