Meta-analysis of the quantity of calcium excretion associated with the net acid excretion of the modern diet under the acid-ash diet hypothesis

Abstract

Meta-analysis of the quantity of calcium excretion associated with the net acid excretion of the modern diet under the acid-ash diet hypothesis [1][2][3][4] Tanis R Fenton, Michael Eliasziw, Andrew W Lyon, Suzanne C Tough, and David A Hanley ABSTRACT Background: The acid-ash diet hypothesis of osteoporosis suggests that acid from the modern diet causes a demineralization of the skeleton, and mobilized bone calcium is excreted. A systematic approach has not been used to summarize the findings of the numerous studies about the hypothesis. Objectives: The purpose of this meta-analysis was to estimate the quantity of net acid excretion and calciuria associated with the modern diet, to assess the association between acid excretion and calcium excretion, and to assess the influence of urine preservatives on calcium measurement. Design: We systematically searched for trials of the acid-ash hypothesis and conducted a meta-analysis. Results: Twenty-five of 105 studies met the inclusion criteria. The estimated quantity of net acid excretion from the weighted average of the control diets from 11 studies was 47 mEq/d. The increase in urinary calcium with a change in renal net acid excretion depended on whether the urine was acidic or alkaline (P 0.001). A significant linear relation was observed between net acid excretion and calcium excretion for both acidic and alkaline urine (P 0.001). The estimated change in urine calcium associated with a change of 47 mEq of net acid excretion in acidic urine was 1.6 mmol/d (66 mg/d) of calcium. Conclusion: Evidence suggests a linear association between changes in calcium excretion in response to experimental changes in net acid excretion. However, this finding is not evidence that the source of the excreted calcium is bone or that this calciuria contributes to the development of osteoporosis.

Diet-Dependent Net Endogenous Acid Load of Vegan Diets in Relation to Food Groups and Bone Health-Related Nutrients: Results from the German Vegan Study

“…With respect to preventive medicine, the near neutral characteristic of the vegan diet is of interest, since it is known that neutral or net base-producing diets have shown multiple health benefits, e.g. decreased urinary calcium excretion and bone resorption [14,16,17,18]. Because vegans tend to consume lower amounts of calcium, lower intake of that bone-related nutrient may be compensated by the ‘calcium-saving effects’ of the neutral character of vegan diets.…”

“…Furthermore, in vitro studies have shown that even a small decrease in pH resulted in a remarkable increase in bone resorption as a result of osteoclast stimulation [11,12,13]. Additionally, net acid-producing diets increase urinary calcium excretion in a dose-dependent manner [14]. Accordingly, it has been hypothesized that net acid-producing diets will induce osteoporosis in the long run [15].…”

Protein intake, calcium balance and health consequences

“…Meta-analysis of studies in which the acid-base intake was manipulated through changes in food intake or supplementation shows a positive correlation between urinary net acid excretion and urinary calcium, with a 0.9-1.4 mg increase in urinary calcium for a 1mEquiv. increase in acid excretion (Fenton et al, 2008(Fenton et al, , 2009. The relationship between acid and calcium excretion is further supported by the fact that addition of base to the diet in the form of sodium bicarbonate partially negates the hypercalciuretic effect of the HP diet (Lutz, 1984).…”

Review of Ca Metabolic Studies and a Model for Optimizing Gastrointestinal Ca Absorption and Peak Bone Mass in Adolescents

“…In Asian pre-pubertal girls consuming a diet containing high protein (1.67 ± 0.58 g×kg/d) and low Ca (433 ± 70 mg/d), protein intake was negatively related to 5-year BMC accretion for the total body and proximal and distal femur (Zhang et al, 2010). However, in another metaanalysis, no evidence of a relationship between protein and calcium accretion was found (Fenton et al, 2008). Thus, the increased loss of Ca in the urine owing to high-protein diets is perhaps offset by the increased Ca absorption or decreased endogenous secretion in humans (Hunt et al, 2009;Kerstetter et al, 2005;Spence et al, 2005) and rats (Engelmann et al, 1975), rather than by decreased bone resorption.…”