Table 2.

Measurements used in literature in estimation dietary acid load

Method	Data Needed	Calculation	Strengths	Limitations
Endogenous Acid Production (EAP)	Dietary intake or 24 hour urine collection	Diet: EAP (mEq/d) = 0.75 × dietary sulfur (mEq/d) + organic anion (OA) production§ Urine: EAP (mEq/d) = urinary sulfate (mEq/d) + OA production§	Easily measured Accounts for differences in sulfur content of different protein sources Can reflect long term intake	Ignores the effect of dietary alkali OA production is variable
Gastrointestinal (GI) alkali absorption	Dietary intake	Diet†: GI alkali absorption (mEq/d)= 0.95 × Na + 0.8 × K + 0.25 × Ca + 0.32 × Mg − 0.95 × Cl − 0.63 × P	Can reflect long term intake	Dependent on accurate nutrient composition databases Assumes average rates of nutrient absorption
Net Endogenous Acid Production (NEAP)	Dietary intake	Direct: NEAP (mEq/d)= EAP − GI alkali absorption Indirect: NEAP (mEq/d) = 54.5 [protein (g/day)/K (mEq/d)] − 10.2	Direct method accounts for all relevant dietary factors Indirect method requires only limited dietary intake data Both can reflect long term intake	Dependent on accurate nutrient composition databases Direct method assumes average rates of nutrient absorption Indirect method assumes sulfur content of all proteins is similar Indirect method assumes mineral cations other than K are negligible
Potential Renal Acid Load (PRAL)	Dietary intake	PRAL (mEq/d) = 0.49 × protein (g/d) + 0.037 × P (mg/d) − 0.021 × K (mg/d) − 0.026 × Mg (mg/d) − 0.013 × Ca (mg/d)‡	Can reflect long term intake	Dependent on accurate nutrient composition databases Assumes sulfur content of all proteins is similar Assumes average rates of nutrient absorption
Net Acid Excretion (NAE)	24 hour urine collection	Direct†: NAE (mEq/d) = NH4+ + TA − HCO3− Indirect†: NAE (mEq/d) = (Cl + P + SO4 + OA§) − (Na + K + Ca + Mg)	Most direct measurement Makes no assumptions about composition of foods, nutrient absorption and sulfur content of proteins	Assumes acid-base equilibrium Reflects short term dietary intake Cumbersome to perform

OA, organic anions; Na, sodium; K, potassium; Ca, calcium; Mg, magnesium; Cl, chloride; P, phosphate; NH₄⁺, ammonium; TA, titratable acidity; HCO₃⁻, bicarbonate; SO₄, sulfate

^†All ions expressed as mEq/d; valence of phosphate is assumed to be 1.8

^‡Some investigators include sodium and chloride in this calculation, but here it is ignored because they are generally balanced in the diet. Calcium is sometimes ignored due to variable GI absorption across individuals. Note dietary input variables here are expressed in different units than GI alkali absorption to be consistent with reporting in the literature.

^§Organic anions can be estimated from body surface area if assumed to be diet independent: OA (mEq/d)=body surface area × 41/1.73; or based on the GI alkali absorption to account for partial diet-dependence: OA (mEq/d)=32.9 + 0.15 × GI alkali absorption(2).