Discover Why Alkaline Ph Food Is Suggested
The old version of this page gave a recipe instead of an answer: a glass of low-fat or semi-skimmed milk, a handful of pistachios (or almonds or walnuts), two or three dry dates and, for anyone who dislikes the taste of milk, a few spoons of instant coffee. It never explained what “alkaline” had to do with any of it. This version does the explaining, and then puts that same glass on the scale researchers use to rank foods by acid load.
Why alkaline food gets suggested at all
The idea behind it is that modern diets “have been suggested to increase systemic acid load and net acid excretion” (Fenton 2011, PubMed 21529374). The effect shows up mainly in urine; blood barely moves. In a 1995 paper, Remer and Manz of the Research Institute of Child Nutrition in Dortmund calculated a “potential renal acid load”, or PRAL, for common foods. Their abstract says the method “allows an appropriate prediction of the effects of diet on the acidity of urine”. It also reports a correlation of r = .83 between the acid the kidneys excrete and urine pH (PubMed 7797810).
Blood is a different matter. Gerry K. Schwalfenberg’s 2012 review in the Journal of Environmental and Public Health notes that human life “requires a tightly controlled pH level in the serum of about 7.4 (a slightly alkaline range of 7.35 to 7.45)”. The same review says urine “may have a variable pH from acid to alkaline depending on the need for balancing the internal environment” (PubMed 22013455). On diet and blood, it adds that a low-carbohydrate, high-protein diet with its higher acid load “results in very little change in blood chemistry, and pH, but results in many changes in urinary chemistry”.
That gap between urine and blood is worth keeping in mind next to product claims. A 2011 systematic review from the University of Calgary, on dietary acid load and bone disease, goes on to note that “alkaline diets and products are marketed to avoid or counteract this acid, help the body regulate its pH” (PubMed 21529374). Among its findings on the proposed bone mechanism: “No study revealed a biologic mechanism functioning at physiological pH.” Schwalfenberg is cautious too. In his conclusion, on bone, he writes that there is “no substantial evidence” that raising urine pH this way helps.
How a food gets its number
A 2013 review by Julia Scialla and Cheryl Anderson gives the PRAL equation in full, per 100 g of food:
PRAL (mEq) = 0.49 × protein (g) + 0.037 × phosphorus (mg) − 0.021 × potassium (mg) − 0.026 × magnesium (mg) − 0.013 × calcium (mg)
A positive result means acid-forming. A negative result means base-forming, which is what “alkaline food” points at. In Scialla’s words, “fruits and vegetables provide alkali” while cheese, meat, eggs and grains “impart a high dietary acid load” (PubMed 23439373). The same paper warns that PRAL is “dependent on accurate nutrient composition databases”, so every figure below says which USDA FoodData Central record it comes from. All of them are SR Legacy records, last updated in April 2019.
The old recipe, one ingredient at a time
Low-fat milk, 1% (FDC 170872), comes out at +0.11 per 100 g, almost exactly neutral. Its protein and phosphorus push the score up by about 5.2. Its potassium, calcium and magnesium pull it down by about 5.1. Schwalfenberg’s Table 2, taken from Remer, lists whole milk at 0.7, so both sources put milk close to zero.
The nuts lean slightly acid. Raw pistachios (FDC 170184) score +2.10 and almonds (FDC 170567) +2.28. Walnuts (FDC 170187) score +5.61, against 6.8 in Schwalfenberg’s table. Neither paper explains the gap; Remer’s table was published in 1995, and these FDC records were last updated in 2019.
Dates are where the glass turns. Deglet Noor (FDC 171726) scores −11.91 per 100 g, and Medjool (FDC 168191) −13.67. Both are lifted by potassium, 656 mg and 696 mg per 100 g, while their protein is low at 2.45 g and 1.81 g.
Instant coffee powder (FDC 171893) is the surprise. At 3,540 mg of potassium per 100 g, it scores −67.49. Nobody spoons in 100 g, though: 2 g of powder comes to about −1.35.
Adding up one glass
Take 250 g of 1% milk (+0.26) and 15 g of pistachios (+0.32). Without dates, the glass sits at about +0.58, mildly on the acid side. Add 30 g of Deglet Noor (−3.57) and the total drops to about −2.99. Stir in 2 g of instant coffee and it reaches about −4.34. Use walnuts in place of pistachios and the glass with dates lands near −2.47.
So in this drink, the dates do most of the “alkaline” work (−3.57 of the −4.92 that the dates and coffee add), and the milk and nuts are close to neutral. That 30 g of dates is also what the NHS counts as a portion of dried fruit. Its 5 A Day page says a 30 g portion of dried fruit, “such as currants, dates, sultanas and figs”, counts as 1 of your 5 A Day, “but should be eaten at mealtimes, not as a snack between meals, to reduce the impact on teeth”.
What the score does not tell you
PRAL estimates a food’s potential acid load on the kidneys from five nutrients. Sugar and calories are not among them. Deglet Noor has 282 kcal and 63.4 g of total sugars per 100 g in FDC, so dates bring energy along with their potassium. Remer and Manz present the score as a way to predict the acidity of urine, and that is the question these numbers answer.
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This article is general food information, not personal dietary advice. If you have a kidney condition or follow a special diet, speak to your doctor or a registered dietitian before changing what you eat.