Mechanism

Cellular Bioenergetics (ATP Production Capacity)

How much ATP each mitochondrion actually makes, measured by 31P-MRS and respirometry, which falls with age faster than mitochondrial number does.

Summary How well do your mitochondria make energy as you age? Show / hide ↓

Cellular bioenergetics means how well mitochondria, the tiny energy-making parts of cells, produce ATP, the cell’s usable energy. In 146 healthy adults aged 19 to 89, muscle ATP production fell about 8% per decade, and about 5% per decade even after accounting for mitochondrial protein, suggesting that function declines beyond simply having fewer mitochondria. Muscle oxygen use and exercise capacity also declined, while older adults had about 17% lower mitochondrial capacity in another comparison. Phosphorus MRS, a scan that measures muscle energy chemistry, found a 21% lower P/O ratio, meaning less ATP was made per oxygen used. Small randomized trials of urolithin A, a compound intended to help remove damaged mitochondria, reported improved muscle endurance, including 95 extra contractions versus 12 with placebo in one 66-person trial; neither trial tested lifespan.

What this means for you: Mitochondria generally produce energy less efficiently with age, and this is supported by several human measurements. The findings are useful for understanding ageing, but they do not show that supplements extend life.

moderate evidence

Evidence tierTier 2, Strong human evidence, hard endpoints or biomarkers

Last verified2026-08-31

Mitochondrial biogenesis asks how many mitochondria a cell has. Cellular bioenergetics asks how well each one works. The two come apart with age, and the functional side declines first.

The reference dataset is a Mayo Clinic study of 146 healthy sedentary people aged 19 to 89, 86 women and 60 men, who had vastus lateralis biopsies and treadmill testing [1]. Mitochondrial ATP production rate fell about 8% per decade per gram of muscle, and still fell about 5% per decade after normalising per milligram of mitochondrial protein, so the loss is not only fewer mitochondria [1]. VO2max fell about 8% per decade, 5% after adjusting for leg lean mass (P < 0.001), and leg lean mass plus ATP production rate together explained 86% of the variance in VO2max [1]. Cytochrome oxidase subunit COX3 abundance fell 10% per decade and COX4 8% per decade, both P < 0.001 [1]. Oxidative DNA damage tracked along: 8-oxo-dG in people aged 65 to 80 sat roughly 25% above those aged 20 to 35, P < 0.01 [1].

Courtney Peterson, Darcy Johannsen and Eric Ravussin collected the muscle-level numbers: in adults aged 70 to 84 versus 20 to 34, citrate synthase activity was 19% lower and mitochondrial capacity 17% lower while OXPHOS protein content was unchanged [2]. Phosphorus MRS in elderly adults showed a 21% lower P/O ratio, meaning less ATP per oxygen consumed [2]. One study found a 50% reduction in oxidative capacity per muscle volume and a 30% reduction per mitochondrial volume [2]. Muscle mass itself declines just under 1% per year, and strength falls about three times faster than mass [2].

Marta Gonzalez-Freire and colleagues confirmed the coupling in the Baltimore Longitudinal Study of Aging: 38 participants aged 24 to 91, mean age 68.6, with ex vivo high-resolution respirometry, post-exercise 31P-MRS, treadmill aerobic capacity and strength testing all moving together [3].

What moves it: urolithin A, a gut metabolite of ellagitannins that triggers mitophagy. Sophia Liu and David Marcinek randomised 66 adults aged 65 to 90, mean age 71.7, to 1,000 mg urolithin A or placebo for 4 months; muscle endurance in the first dorsal interosseus rose by 95.3 contractions to fatigue against 11.6 on placebo at 2 months [4]. Anurag Singh's 88-person ATLAS trial in overweight sedentary adults aged 40 to 65 tested 500 mg and 1,000 mg for 120 days with no exercise programme [5]. Neither trial measured lifespan.

References

Every numbered citation in this entry links here. Each reference links out to the primary source.

[1]

Decline in skeletal muscle mitochondrial function with aging in humans Tier 2

Mayo Clinic aging and muscle metabolism group · 2005 · PNAS

N=146 aged 19-89; ATP production rate -8%/decade per gram muscle, -5%/decade per mg mitochondrial protein; VO2max -8%/decade; COX3 -10%/decade, COX4 -8%/decade, both P<0.001.
[2]

Skeletal Muscle Mitochondria and Aging: A Review Tier 4

Courtney M Peterson, Darcy L Johannsen, Eric Ravussin · 2012 · Journal of Aging Research

Adults 70-84 vs 20-34: citrate synthase -19%, mitochondrial capacity -17%, P/O ratio -21%; muscle mass declines just under 1% per year.
[3]

Skeletal muscle ex vivo mitochondrial respiration parallels decline in vivo oxidative capacity, cardiorespiratory fitness, and muscle strength: The Baltimore Longitudinal Study of Aging Tier 3

Marta Gonzalez-Freire, Paolo Scalzo, Joseph D'Agostino, et al. · 2018 · Aging Cell 17:e12725

Baltimore Longitudinal Study of Aging, N=38 aged 24-91, mean 68.6; ex vivo respirometry parallels 31P-MRS oxidative capacity, fitness and strength.
[4]

Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial Tier 1

Sophia Liu, Davide D'Amico, Eric Shankland, David J Marcinek, et al. · 2022 · JAMA Network Open 5(1):e2144279

RCT, N=66 aged 65-90, 1,000 mg urolithin A for 4 months; FDI muscle endurance +95.3 contractions vs +11.6 placebo at 2 months.
[5]

Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults Tier 1

Anurag Singh, Davide D'Amico, Penelope A Andreux, et al. · 2022 · Cell Reports Medicine 3(5):100633

ATLAS RCT, N=88 overweight sedentary adults aged 40-65, 500 mg or 1,000 mg urolithin A for 120 days, no exercise programme.

References

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Further reading