Foods contain substances impacting the acid-base balance. The Western diet is often viewed as being overly acid due to its high-level of animal-based protein and low-level of vegetable intake. Meanwhile, with ageing the ability to excrete acid compounds is reduced as kidney function declines and so there is a risk of acid retention and subsequent interstitial acidosis. Two systems used for calculating the Dietary Acid Load (DAL): the potential acid load of foods (PRAL) and the net endogenous acid production (NEAP). This report outlines weaknesses in these formulas and concludes that dietitians and nutritionists lack the necessary tools to research the acid-base hypothesis. Additionally, the report emphasizes the importance of food selection in the ageing population. Background: Foods contain substances impacting the acid-base balance. The Western diet is often viewed as being overly acid due to its high-level of animal-based protein and low-level of vegetable intake. There are concerns that the disproportionate acid intake promotes low-grade metabolic acidosis in the interstitial fluid, interstitial acidosis, and may lead to chronic disease. Two formulas are used for calculating the DAL: the PRAL and the NEAP. Both PRAL and NEAP are based on levels of protein and minerals. Aim: To identify additional food constituents that impact DAL. Methods: Review of the literature concerning the acid-forming and alkaline-forming constituents of foods. Results: Five additional food constituents were identified as potentially having a meaningful impact on DAL. The oxidation of taurine and the metabolism of fructose and purines increase acidity, whereas organic acids increase alkalinity. Additionally, polyphenols affect the microbiota which break down uric acid excreted in the intestinal tract. Conclusions: Neither PRAL nor NEAP provides complete assessments of the impact of foods on DAL. These formulas could be improved by the inclusion of dietary amino acids rather than protein, taurine, purines, fructose, organic acids and polyphenols. Currently, dietitians and nutritionists lack the necessary tools both to research the acid-base hypothesis and recommend managed diets. Managed diets are of particular importance for the elderly because of their reduced kidney function which increases the risk of acid retention and subsequent interstitial acidosis.
Keywords: Acid-base balance; NEAP; PRAL; daily acid load; interstitial acidosis; interstitial fluid; protein.