PRAL, Mortality Risk, and Lifespan

Within the body, meat, grains, and nuts are generally acid-forming, whereas vegetables and fruits are alkaline-forming. Is the distinction between whether your diet is acid- or alkaline-forming important for optimal health and lifespan? In an earlier post, I discussed the importance of PRAL (potential renal acid load) by correlating it with serum bicarbonate and mortality risk (

More recent data (a 15-year study of 81, 697 older adults; average age ~61y; Xu et al. 2016) has examined the association between PRAL with risk of death from all causes. In women, acidic PRAL values ( > 0) were associated with a significantly increased risk of death from all causes, as were alkaline PRAL values (< -5.6). In addition, very acidic (~40) and very alkaline (-30) PRAL values were associated with the highest risk for all-cause mortality:


Similarly, in men, when compared with a PRAL = 0, both alkaline (PRAl < -5.6) and acidic (> 29.8) values were associated with increased all-cause mortality risk.


While this data suggests that eating too much meat, grains, and/or nuts may not be optimal for health, it also suggests that eating too much alkaline-forming food, including veggies and fruits, may also not be optimal! My high veggie-based diet yields a very negative PRAL, ~-120 (~ -0.05 PRAL units/calorie), which would seem to put me at increased all-cause mortality risk. To further investigate, I decided to look at the PRAL values of long-lived societies.

Life expectancy for those who live on the island of Okinawa is among the longest in the world (Miyagi et al. 2003). What’s the average daily PRAL value for Okinawan older adults?  The PRAL formula, as reported by Remer and Manz (1994) is:

PRAL = (0.49 * protein intake in g/day) + (0.037 * phosphorus intake in mg/day) – (0.02 * potassium intake in mg/day) – (0.013 * calcium intake in mg/day) – (0.027 * magnesium intake in mg/day).

The daily dietary data for 75-year old Okinawans (Willcok et al. 2007), including total calories: 1785, protein: 39g, phosphosphorus: 864 mg, potassium: 5200 mg, calcium: 505 mg, and magnesium: 396 mg, yields a PRAL value = -87.4! Because higher amounts of these nutrients can result from an increased calorie intake, it’s important to divide PRAL by the average daily calorie value, thereby yielding PRAL/calorie =  -0.049. Interestingly, these values are very close to my very alkaline PRAL values of -121, and PRAL/calorie = ~-0.05!

My goal is not just to get to 75 in great health, but to live past 100 (and far beyond). What’s the data in centenarians? Unfortunately, I could only find 1 study that included dietary data for that age group.

In a study of 104 Japanese centenarians (average age, 100y; Shimizu et al. 2003) daily dietary values of 1137 calories, 44g protein, 676 mg phosphorus, 1695 mg potassium, 414 mg calcium, and 154 mg magnesium were reported, thereby yielding an average daily PRAL value = -16.3, and PRAL/calorie = -0.014. In contrast to the data of Xu et al. (2016), these data suggest that an alkaline diet may indeed be optimal for lifespan.

So what’s your dietary PRAL value?


Miyagi S, Iwama N, Kawabata T, Hasegawa K. Longevity and diet in Okinawa, Japan: the past, present and future. Asia Pac J Public Health. 2003;15 Suppl:S3-9.

Remer T, Manz F. Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein. Am J Clin Nutr. 1994;59:1356-1361.

Shimizu K, Takeda S, Noji H, Hirose N, Ebihara Y, Arai Y, Hamamatsu M, Nakazawa S, Gondo Y, Konishi K. Dietary patterns and further survival in Japanese centenarians. J Nutr Sci Vitaminol (Tokyo). 2003 Apr;49(2):133-8.

Willcox BJ, Willcox DC, Todoriki H, Fujiyoshi A, Yano K, He Q, Curb JD, Suzuki M. Caloric restriction, the traditional Okinawan diet, and healthy aging: the diet of the world’s longest-lived people and its potential impact on morbidity and life span. Ann N Y Acad Sci. 2007 Oct;1114:434-55.

Xu H, Åkesson A, Orsini N, Håkansson N, Wolk A, Carrero JJ. Modest U-Shaped Association between Dietary Acid Load and Risk of All-Cause and Cardiovascular Mortality in Adults. J Nutr. 2016 Aug;146(8):1580-5.