One reason alkaline pH food is recommended comes from sport. A 2020 paper on Lithuanian athletes states that keeping alkaline circumstances in the body is important for athletic performance, in training and in competition. That idea has been put to the test. Below is how the “alkaline” label is worked out for a food, what four published exercise diet trials found, and where dates come out on that scale.
How a food gets called alkaline
Researchers sort foods with a number called the potential renal acid load, or PRAL. A 2013 review by Scialla and Anderson gives the equation: 0.49 × protein (g) + 0.037 × phosphorus (mg) − 0.021 × potassium (mg) − 0.026 × magnesium (mg) − 0.013 × calcium (mg). A positive result means a food adds to the acid load. A negative result means it pushes the other way, which is what people mean by an alkaline food.
The same review lists one weakness of these estimates: they are “dependent on accurate nutrient composition databases”. So the score is only as good as the food data fed into it.
A team at Saint Louis University described the two kinds of diet in plain terms. In their words, low-PRAL (alkaline promoting) diets are characterised by high intakes of vegetables and fruits with limited consumption of meats, cheeses and grains, and high-PRAL diets by the opposite pattern.
Trial one: a longer run to exhaustion
That Saint Louis group, led by Caciano and published in 2015, put people on a low-PRAL diet and, on a separate occasion, a high-PRAL diet. Each diet ran for 4 to 9 days, until fasted morning urine turned alkaline or acid. The anaerobic test was a running time-to-exhaustion test lasting 1 to 4 minutes. After the low-PRAL diet, time to exhaustion was 21% greater than after the high-PRAL diet. The authors also saw a strong tendency toward lower RER values at 70% of VO2max, which, they wrote, appears to shift fuel use toward fat and spare carbohydrate.
Trial two: blood changed, sprint power did not
A German crossover trial by Limmer and colleagues (2020) gave 15 physically active adults, average age 24.5, four days of an alkalising diet and four days of an acidising diet. They then ran a tethered sprint test, both in normal air and after 12 hours in low-oxygen air. Urine pH, blood pH, blood bicarbonate and base excess were all higher after the alkalising diet. Peak force, mean force and fatigue index did not differ between the two diets.
Trial three: no change in blood pH
In Finland, Hietavala and colleagues (2012) used PRAL to design a low-protein vegetarian diet meant to raise base production. Nine recreationally active men followed it for 4 days and, in the other arm, ate normally. Venous blood pH and bicarbonate did not differ between the diets, at rest or while cycling. Time to exhaustion did not change either. Oxygen use was higher at the 40, 60 and 80% of VO2max stages, which the authors took to mean that exercise economy was poorer.
Trial four: diet plus bicarbonate water
A French study of 22 highly trained athletes (Chiron, 2024) put everyone on an alkalising diet for a simulated three-day 400 m race. Half also drank bicarbonate-rich water, and half had placebo water. Only the bicarbonate-water group improved in the third race. Both groups ate the alkalising diet, so the study did not compare it with a normal diet. The paper states it was funded by ALMA Source groupe.
So why is it recommended?
The four trials point in different directions. One found a longer run to exhaustion, two found no change in performance, and one showed a gain only in the group that also drank bicarbonate water. In the two trials that compared an alkalising diet with an acid-forming one (Caciano and Limmer), urine pH moved with the diet.
The clearest recommendation in this set comes from a 2020 survey of 323 Lithuanian high-performance athletes by Baranauskas and colleagues. It found that 25 to 30% of them ate high-protein diets of 2.0 to 4.8 g per kg a day, which led to a dietary acid-base imbalance. The authors’ advice was that athletes consume higher amounts of potassium and magnesium. Potassium and magnesium are two of the terms that pull a PRAL score down in the equation above.
Where dates land
None of these trials tested dates. Their PRAL can still be worked out from USDA FoodData Central figures with the equation above. Per 100 g, Medjool dates (record 168191) carry 1.81 g protein, 62 mg phosphorus, 696 mg potassium, 54 mg magnesium and 64 mg calcium, which gives a PRAL of about −13.7. Deglet Noor dates (record 171726) work out at about −11.9. A 30 g portion, which the NHS counts as one of your 5 A Day for dried fruit such as dates, comes to about −4.1 for Medjool and −3.6 for Deglet Noor.
The NHS adds that dried fruit should be eaten at mealtimes, not as a between-meal snack, to reduce the risk of tooth decay. So dates eaten with a meal fit both the NHS advice and the low-PRAL pattern. They are not a sports supplement, and the trials above give no reason to treat them as one. Questions about diet and training belong with a GP or a dietitian.
More about this site is on the About Us page and the contact page, and other articles are on the blog.