The potential renal acid load score that Remer and Manz used to rank foods is built from five nutrients. In 1998 a team at the University of California, San Francisco, published a shorter estimate that needs only two: protein and potassium. This article uses that shortcut to look at an ordinary plate of rice and chicken, then asks how many dates it would take to tip the plate the other way. The answer says a lot about what alkaline pH food lists can and cannot do.
The two-number shortcut
Frassetto and colleagues (PubMed 9734733) studied 141 subjects eating 20 different diets. They used renal net acid excretion as their measure and asked which parts of the diet predicted it. Protein pushed the number up and potassium pushed it down, and the two were not correlated with each other. Their reason for picking these two is stated plainly: sulfuric acid produced from protein metabolism, and bicarbonate from the potassium salts of organic acids in food, are the major parts of the acid load that change with diet.
The result was one line: net acid excretion = 62 × (protein ÷ potassium) − 17.9, with protein in grams and potassium in milliequivalents. The protein-to-potassium ratio alone accounted for 71% of the variation between diets.
A milliequivalent of potassium is about 39.1 mg, since the element's atomic weight is 39.0983 and it carries a single charge. Work the equation backwards and the zero point falls at a ratio of about 0.29. In everyday units, a whole day's eating breaks even at roughly 7.4 grams of protein for every 1,000 mg of potassium. More protein than that per 1,000 mg pushes the estimate to the acid side. Less pulls it the other way.
Where common foods fall on that line
Here are a few foods from USDA FoodData Central (FDC), expressed as grams of protein per 1,000 mg of potassium:
- Medjool dates (FDC 168191): about 2.6 g
- Raw banana (FDC 173944): about 3.0 g
- Deglet Noor dates (FDC 171726): about 3.7 g
- Raw spinach (FDC 168462): about 5.1 g
- Cooked white rice (FDC 168878): about 77 g
- Roast chicken breast (FDC 171477): about 121 g
The fruit and the spinach all sit under the 7.4 g line. Rice is ten times over it, and chicken more than sixteen times. The equation was built for whole diets, not single foods, so these figures show which way each food pulls rather than a score for eating it alone.
One plate, worked through
FDC gives a cup of cooked white rice as 158 g and one roasted chicken breast, bone and skin removed, as 86 g. Together they bring about 30.9 g of protein and 275 mg of potassium. That is about 112 g of protein per 1,000 mg of potassium, some fifteen times the break-even line.
Add a cup of raw spinach (30 g in FDC) and the plate drops to about 72 g per 1,000 mg. Finish with a 30 g portion of Deglet Noor dates, the size the NHS counts as one of your 5 A Day for dried fruit, and it falls to about 51 g. Each step moves the plate in the right direction. None of them comes close to the line.
How many dates would it take?
Solve the same equation for dates alone. To bring that rice-and-chicken plate to the zero point you would need about 1.2 kg of Deglet Noor, which FDC puts at roughly 3,400 kcal. Medjool, with less protein and more potassium per 100 g, would take about 870 g, or around 2,400 kcal. Either way, that is more energy than the 2,000 kcal a day the NHS says an average woman needs. The Deglet Noor figure is above the 2,500 kcal it gives for an average man as well.
So the shortcut makes a point that a list of "alkaline foods" hides. On this plate, the chicken and the rice set the ratio. A portion of fruit on the side changes it, but it cannot cancel a plate that is far over the line.
What the shortcut leaves out
The longer formula, printed in Scialla and Anderson's 2013 review (PubMed 23439373), also counts phosphorus, magnesium and calcium. Gerry Schwalfenberg's 2012 review (PubMed 22013455) says foods can be categorized by their potential renal acid load, the score that formula produces. The two-number version gives up some accuracy for convenience. In the 1998 data, 29% of the variation between diets was left unexplained by the ratio.
What "required" can mean here
Schwalfenberg describes a tightly controlled serum pH of about 7.4, between 7.35 and 7.45, while the urine may vary from acid to alkaline depending on the need to balance the internal environment. Remer and Manz (PubMed 7797810) found a correlation of r = .83 between net acid excretion and urine pH, and wrote that their method predicts the effects of diet on the acidity of urine. Both formulas, then, estimate something that shows up in the urine. The blood, on Schwalfenberg's account, stays in its narrow range.
For a reader who wants to apply the idea, the protein-to-potassium ratio is the easiest version to use with real food. The fruit and spinach in the list above lower it. In the worked plate above, the chicken and rice raised it far more than a side of fruit could offset. Dates fit on the low side of the line, but as one portion beside a meal, not as a counterweight to it.
About this site and where to ask
The about page describes Sayer Dates as serving everyone from retail buyers to wholesale supply, with orders delivered across the country. For questions, quotes or orders, the contact page gives a WhatsApp number, and more date articles are on the blog. A link kept from the earlier version of this post points to Kurma Mazafati Malaysia.
The video below is from the YouTube channel AbuAyyash Farms, titled as a look at Medjool date farming and a date processing factory.
This article is general information about food composition, not personal advice. If you have a health condition or take regular medication, speak to your doctor before making big changes to what you eat.