Edible insects exert a high potential renal acid load to the human kidneys

ABSTRACT The potential renal acid load (PRAL) describes the capacity of a food to produce acid or base in the human body. The long-term consumption of high-PRAL diets induces a chronic low-grade metabolic acidosis state that has been associated with inflammation and impaired kidney function. PRAL tables are available to help individuals in selecting low-PRAL foods. However, these tables do not cover novel or uncommon foods in Western societies. Entomophagy – the practice of eating insects is an emerging trend in the Western world with unclear health consequences from an acid-base perspective. Here, we hypothesized that the consumption of insects is associated with a high PRAL, and analyzed the PRAL values of n = 39 commonly consumed edible insects. Our results suggest that the majority of edible insects have very high PRAL values (of up to 43.62 mEq/100 g), indicating strong acidifying properties and likely resulting in acid retention. PRAL values of edible insects rank well above the PRAL values of other high-protein foods, including legumes, pork and beef. PRAL was moderately correlated with the protein content (r = 0.42) and phosphorus content (r = 0.50) of the examined edible insects. Our data point to a potential health concern when regularly consuming edible insects.


Introduction
Diet composition may alter acid-base balance in humans by providing acid or base precursors. [1,2]igh-protein foods such as meat, cheese and eggs increase the production of acid in the human body, whereas most plant-based foods decrease it by generating alkalis. [2,3]This happens upon the metabolization of potassium salts of organic anions (mainly malate and citrate), which undergo combustion in the human body to yield bicarbonate and which consume hydrogen ions. [4,5]The overall capacity of acid or base production of any food is called potential renal acid load (PRAL). [1]he long-term consumption of high-PRAL diets induces a chronic low-grade metabolic acidosis state, which has been associated with systemic inflammation and tissue damage in the human body. [6,7]This might be particularly detrimental in individuals with chronic kidney disease and reduced buffering capacities, who benefit from a low-PRAL diet. [8,9]o accomplish this goal, PRAL quantification is of paramount importance.PRAL tables can assist individuals to achieve this, [10] as they contain the PRAL values of commonly consumed foods and systematically categorize food items into alkaline and acidic foods.However, PRAL values are not yet available for all food items and non-existent for novel and previously rather uncommon foods in Western countries.One example is the group of nondairy plant-based milk alternatives, for which we recently published a systematic PRAL analysis. [11]Another food group that has received little to no attention from an acid-based perspective in the past includes edible insects.
Entomophagy -the practice of eating insects -is an emerging trend in the Western world. [12]upporters of entomophagy argue that edible insects are a sustainable and healthy food choice, [12] whereas critics raise ethical and animal welfare concerns. [13,14]Additional arguments against entomophagy include the presence of anti-nutrients as well as potentially allergic or toxic substances encountered in insects.Although these aspects should not be ignored, entomophagy is a rising trend.This trend, however, has unknown consequences for PRAL, kidney health and the acid-base equilibrium in humans.
To the best of our knowledge, negligible work on the PRAL values of edible insects have been reported in the scientific literature.Yet, many edible insects are abundant in protein and phosphorus, [15] which are the major PRAL contributors. [10]Thus, questions arise as to how the consumption of edible insects affects PRAL and whether there are noticeable differences between different insect groups.At this stage, it is also unclear how the PRAL value of edible insects fares in comparison to the PRAL value of other important protein sources for humans, including legumes and traditional meat products.
In this short contribution, we hypothesized that the consumption of edible insects is associated with elevated PRAL values.To test our hypothesis, we analyzed the PRAL values of n = 39 edible insects commonly consumed around the globe.

Study population and design
Nutrient content of edible insects was extracted from previous publications in the field.Reviews examining the nutrient content of edible insects were identified using the following search engines: PubMed, Google Scholar and Web of Science.These databases were searched using various combinations of the following search terms: edible insects; entomophagy; consumption; nutrient content; protein.Exploratory in nature, the literature search was not designed to reflect a systematic review.Nevertheless, cross-references and reference lists of the included articles and cited reviews were manually screened for additional articles to ensure an adequate sample size.Only data from edible insects with a complete nutrient profile required for PRAL estimation (including protein, potassium, phosphorus, magnesium and calcium) was extracted.We considered only articles in English or German language.The entire review process was conducted by the authors in April 2023.

DAL estimations
We estimated PRAL (in mEq/100 g) based on the following validated formula by Remer et al. [16] PRAL mEq=100g The PRAL score is a validated method to calculate the estimated acid-base impact of foods.It considers ionic dissociation, intestinal absorption rates for the included micro-and macronutrients and sulfur metabolism. [1]

Statistical analysis
We calculated PRAL values in mEq/100 g for each analyzed edible insect.We used histograms, box plots and Stata's Shapiro -Wilk test to check whether data was normally distributed or not.For normally distributed variables, we provided the mean and its corresponding standard deviation.For non-normally distributed variables we presented medians and the corresponding interquartile ranges in parenthesis.Pearson's product-moment correlations and Spearman's rank-order correlations were run to assess the relationship between the content of selected nutrients and PRAL for all examined insects.Scatterplots, boxplots and heatplots were created to visualize the results.Scatterplots were supplemented with overlaid linear prediction plots for illustrative purposes (blue dashed line = line of best fit).All analyses were performed with STATA 14 statistical software (StataCorp.2015.Stata Statistical Software: Release 14. College Station, TX: StataCorp LP).
Figure 3 displays a scatterplot, visualizing the significant association between PRAL and edible insects' phosphorus content.In a similar style, scatterplots were constructed for potassium (Figure 4) and protein (Figure 5).Correlation coefficients may be obtained from the respective figure legends.Finally, Figure 6 summarizes the results of all bivariate correlation analyses in a heatplot (based on n = 38 observations).Significant associations were marked with an asterisks.

Discussion
While traditionally common in tropical and subtropical regions, entomophagy is now also a rising trend in the Western world. [17]Supporters of entomophagy argue that insects are an important source of animal protein, with a crude protein proportion ranging from 40% to 75% based on a dry weight basis. [17]Entomophagy advocates also argue that edible insects contain more crude protein than conventional meat.They are also considered a good source of vitamins.Edible insects generally have a high protein digestibility that can exceed 90% [23] -a fact that should be considered in the discussion about the PRAL values estimated in this study.
As displayed in Table 1, some insects are also abundant in phosphorus -another main PRAL contributor besides protein.For the aforementioned reasons, one would intuitively expect high PRAL values from a 100 g portion of any edible insect.Then again, some insects are at the same time rich in potassium, which is the most important alkali precursor.One particular example is Bombyx mori, with approximately 1800 mg potassium/100 g.In light of these specific nutrient content patterns and with regard to the absolute nutrient content dimensions, we deemed it necessary to precisely estimate the PRAL values of edible insects.
Our results suggest that edible insects generally exert a high PRAL to the human kidneys.The high potassium content found in edible insects may not compensate for the high protein and phosphorus content from an acid-base perspective.Instead, it substantially contributes to the overall daily potassium intake and could be of particular risk in patients with chronic kidney failure who are usually instructed to play close attention to their potassium intake.
Since edible insects are more and more commonly consumed in Europe and North America, [12] we believe that entomophagy advocates should be aware of this phenomenon, and should take into account the high PRAL exerted to the human kidneys when eating insects.To the best of our knowledge, we are the first group to glance at edible insects from an acid-base perspective.
While the estimated PRAL values were rather inhomogeneous in the herein presented sample, our results suggest that the majority of edible insects have very high PRAL values (of up to 43.62 mEq/100 g).To the best of our knowledge, PRAL values of this level are unprecedented and rank well above the PRAL values of other unprocessed high protein foods.Green beans, for example, are alkaline, with a PRAL value of −3.1 mEq/100 g.Pork and beef, on the other hand, are acidifying, and yield PRAL values of approximately 8 mEq/100 g each.Edible insects have an even higher PRAL value and should thus be considered with great caution by individuals who wish to adopt an alkaline or near-alkaline diet.
The capacity of the human's body to buffer the acid load from diet is generally limited.In healthy people with a normal kidney function, acid retention occurs once the amount of acid that gets excreted out in the urine is > 0.4-1 mEq/kg of body weight per day (eg, 40-70 mEq/day for a 70 kg adult). [7]estern diets are usually characterized by a total dietary acid load ranging from 50 to 100 mEq/day, and frequently lead to acid retention with subsequent low-grade metabolic acidosis. [2]In light of this phenomenon, it is important to recognize the high PRAL values of edible insects -even when considering low intake quantities (e.g.50 or 100 g/day).Adding edible insects to the menu might therefore result in even greater PRAL values and greater acid retention.
Our data generally suggest that insects are not suitable for individuals with reduced buffering capacities (e.g.older adults or patients with impaired kidney function, [24] who should instead rely on high quality plant-based protein with alkalizing properties.As a logical consequence, a high concomitant intake of alkaline plant foods would be required to offset the acid burden from edible insects -even in healthy adults.
This short contribution draws upon a number of strengths but has also limitations that warrant a further discussion.To the best our knowledge, we are the first group to report PRAL values of edible insects.While the sample size is moderate, we were not able to identify a larger number of insects with a complete nutrient profile required for PRAL calculation.Cross-sectional in nature, our data offer no insights how the addition of edible insects to menus would alter overall PRAL scores.Future studies should therefore quantify this in greater detail and should also consider urinary PRAL markers.Despite these limitations, we deem our analysis to be important and call for additional studies in this particular field.

Conclusion
The consumption of edible insects exerts a high PRAL to the human kidneys.This likely results in acid retention in individuals with an otherwise low alkali intake.Future studies are warranted to obtain a deeper understanding of this underexplored topic.In the meantime, our data point to a potential health concern when regularly consuming edible insects.

Figure 1 .
Figure 1.The phosphorus and potassium content of edible insects.Micronutrients shown in mg/100 g edible portions.Based on n = 39 observations.

Figure 2 .
Figure 2. The magnesium and calcium content of edible insects.Micronutrients shown in mg/100 g edible portions.Based on n = 39 observations.

Figure 3 .
Figure 3. Scatterplot showing the positive association between PRAL and phosphorus content of edible insects.Phosphorus content in mg/100 g; PRAL in mEq/100 g.The Pearson's product-moment correlation coefficient was 0.50 (p = .001).Based on n = 39 observations (red dots).Blue dashed line = line of best fit.

Figure 4 .
Figure 4. Scatterplot showing the inverse association between PRAL and potassium content of edible insects.Potassium content in mg/100 g; PRAL in mEq/100 g.The Pearson's product-moment correlation coefficient was -0.47 (p = .002).Spearman's rho was -0.23 but not statistically significant (p = .16).Based on n = 39 observations (red dots).Blue dashed line = line of best fit.

Figure 5 .
Figure 5. Scatterplot showing the positive association between PRAL and protein content of edible insects.Protein content in g/100 g; PRAL in mEq/100 g.The Pearson's product-moment correlation coefficient was 0.42 (p = .009).One outlier (protein content per 100 g: >70 g) in the sample was removed for analytical purposes.Based on n = 38 observations (red dots).Blue dashed line = line of best fit.

Table 1 .
Nutrient content and resulting potential renal acid load values of selected edible insects: an overview.