Acid-Base Balance

What acid-base balance means for longevity

Your blood pH sits between 7.35 and 7.45. That's a remarkably tight window, and your body defends it aggressively through buffering systems, lung ventilation, and kidney filtration. The idea that you can dramatically shift your blood pH through diet is wrong. But the metabolic cost of maintaining that pH under a high acid load? That's where the longevity story gets interesting.

With age, kidney function declines. The ability to excrete hydrogen ions and regenerate bicarbonate weakens gradually, leading to what researchers call low-grade chronic metabolic acidosis. A large prospective study from the Health, Aging, and Body Composition cohort found that older adults with low serum bicarbonate (below 23 mEq/L) had a 24% higher risk of all-cause mortality, independent of kidney disease status ^[1].

How chronic acid load damages muscle and bone

Chronic low-level acidosis forces the body to pull calcium and other alkaline minerals from bone to buffer excess acid. Over years, this contributes to reduced bone mineral density and increased fracture risk ^[2]. At the same time, acidosis stimulates muscle protein breakdown through glucocorticoid-dependent proteolysis. The result is a double hit: weaker bones and less muscle mass, both hallmarks of frailty in older adults.

Research on potassium bicarbonate supplementation shows this process can be slowed or partially reversed. In postmenopausal women, bicarbonate supplementation significantly reduced urinary nitrogen loss, a marker of muscle protein breakdown ^[3]. A separate trial found that bicarbonate treatment improved lower-extremity muscle power in older adults over three months ^[4].

Dietary acid load and the PRAL score

The Potential Renal Acid Load (PRAL) score estimates how much acid or base a food generates after metabolism. Meat, cheese, grains, and processed foods score high on the acid side. Fruits, vegetables, and legumes are alkaline-forming. A 2024 review in Nutrients linked high dietary acid load to faster kidney function decline, insulin resistance, hypertension, and increased frailty in older adults ^[5].

This doesn't validate the "alkaline diet" as marketed. You can't alkalinize your blood with lemon water. But the pattern holds: diets rich in potassium-containing produce reduce the metabolic burden on kidneys and preserve muscle and bone tissue with aging. One study found that subjects with the highest potassium intake retained 1.64 kg more lean tissue mass compared to those consuming half as much ^[6].

Practical takeaways for healthspan

The evidence points toward a simple conclusion: eat more vegetables and less processed food. Not because these foods "alkalize" your blood, but because they reduce the acid load your aging kidneys have to handle. Adequate potassium, magnesium, and calcium intake through food supports the buffering systems that keep pH regulation running smoothly. For people with compromised kidney function, monitoring serum bicarbonate levels may offer an early warning signal worth tracking as a biomarker.