Ca-AKG and biological age: the Rejuvant story, the ABLE trial, and what we actually know

Ca-AKG has not been shown to reverse human aging. The human biological-age story is based on observational DNA-methylation data from users of a proprietary controlled-release product, plus an ongoing randomized trial whose efficacy results have not yet been published.

The famous “eight years younger” number comes from a small 2021 retrospective study. A much larger 2026 cohort found a far smaller cross-sectional association — and the longitudinal signal did not remain significant after fuller adjustment.

This page separates those findings from the marketing shorthand.

What does “biological age” mean here?

The Ca-AKG studies discussed on this page use DNA methylation clocks: algorithms that estimate age-related molecular patterns from methylation at selected genomic sites.

These clocks are biomarkers, not direct measurements of lifespan or disease prevention. A lower methylation-age estimate does not automatically mean that someone will live longer, avoid dementia, prevent cardiovascular disease or reduce cancer risk.

The Rejuvant studies used TruAge, a proprietary saliva-based clock. In the larger 2026 cohort, the authors reported only moderate short-term test–retest reliability for the assay, with an intraclass correlation around 0.45–0.50. That matters when interpreting change in individuals.

The 2021 Rejuvant study: where “8 years younger” came from

In 2021, researchers retrospectively analyzed 42 self-selected adults who had used Rejuvant — a sustained-release Ca-AKG product combined with vitamin A in the male formulation or vitamin D in the female formulation — and had TruAge testing before and after supplementation [1].

After an average of about seven months, the reported mean reduction in TruAge biological age was 7.96 years.

That number is real as a reported biomarker result. It is not equivalent to proving that participants became eight years “younger” in a clinical sense.

The study had no placebo group, no randomization, only 42 participants, self-selection into supplement use and testing, and commercial relationships involving both the product and the clock. Rejuvant also contains added vitamins, so the isolated contribution of Ca-AKG cannot be determined.

The correct interpretation is hypothesis-generating observational evidence.

The 2026 cohort: 4,260 people, a much smaller effect

A 2026 Aging Cell study analyzed 4,260 unusually health-conscious adults who had taken TruAge testing and reported supplement or medication use [2].

Delayed-release AKG users had an average Age Residual about 1.8 years lower than non-users in cross-sectional analysis. The association remained significant after adjustment for age, sex, smoking, health status and additional covariates. A matched analysis showed a smaller difference of about 1.27 years.

Plain non-delayed AKG showed a smaller, statistically non-significant association.

That is important, but it is still observational. Users were not randomly assigned to supplements, exposure was largely self-reported, dose and duration were incompletely characterized, and the cohort was unusually healthy compared with the general population.

The longitudinal result is the most important caveat

The 2026 study also included people with repeated testing.

Only 26 self-declared delayed-release AKG users had multiple tests. When a broader delayed-release subscriber group was analyzed, the unadjusted odds ratio for improvement was nominally significant, but the association became non-significant after adjustment for baseline Age Residual and regression to the mean [2].

That does not prove the cross-sectional association is false. It does mean the dataset does not establish that starting delayed-release Ca-AKG causes a biological-age reduction over time.

Why the 2021 and 2026 results should not be treated as equivalent

The effect sizes are very different.

The 2021 retrospective reported an average reduction close to eight years. The much larger 2026 cross-sectional analysis found an association closer to 1.8 years, and the adjusted longitudinal result was not significant.

That gap is one reason the “eight years younger” marketing line should not be treated as the best current estimate of a Ca-AKG effect.

Does controlled release explain the difference?

We do not know.

The 2026 cohort found a stronger cross-sectional association for delayed-release AKG than for plain non-delayed AKG. But it was not a randomized head-to-head formulation trial.

The delayed-release product also contained vitamins, users came through different recruitment channels, and unmeasured health behaviors could differ between groups. So the study cannot tell us whether release kinetics, the added vitamins, user characteristics or some combination explains the difference.

A standard Ca-AKG capsule therefore should not borrow Rejuvant's biological-age result. But the same data also do not prove that standard Ca-AKG has no effect.

What does ABLE add?

ABLE is the most important randomized human study for this question.

The published protocol describes a single-center, randomized, double-blind, placebo-controlled trial in 120 adults aged 40–60 whose DNA methylation age exceeded chronological age. Participants receive 1 g/day sustained-release Ca-AKG or placebo for six months, followed by three months of follow-up [3].

The primary endpoint is change in DNA methylation age using a composite of four established clocks: Hannum, Horvath, GrimAge and PhenoAge. Secondary outcomes include inflammatory and metabolic blood markers, muscle strength, arterial stiffness, aerobic capacity, body composition, bone density and other measures.

A 2025 peer-reviewed recruitment paper confirmed that 120 participants were enrolled [4].

Neither the protocol nor the recruitment paper reports efficacy or safety outcomes. As of September 20, 2026, our audited Ca-AKG evidence database does not contain a published ABLE outcome paper.

What do the mouse lifespan studies add?

The animal evidence is relevant background, but it is no longer a one-study story.

The 2020 Shahmirzadi study reported improved frailty measures in both sexes and a statistically significant lifespan benefit in female C57BL/6 mice, while male lifespan was not significantly extended [5].

The US National Institute on Aging Interventions Testing Program later tested AKG in genetically heterogeneous UM-HET3 mice at multiple sites. A late-start experiment did not extend lifespan [6], and a second experiment starting AKG earlier also found no lifespan extension [7].

That makes the preclinical lifespan evidence mixed. It cannot be used as independent confirmation that a methylation-age change in humans represents slower organismal aging.

Does Ca-AKG lower biological age?

The most defensible 2026 answer is:

• Rejuvant users show a cross-sectional association with lower DNA methylation age.
• The larger 2026 estimate is much smaller than the original eight-year retrospective headline.
• The adjusted longitudinal signal was not significant.
• Plain non-delayed AKG did not show a statistically significant association in the same cohort.
• No completed randomized Ca-AKG trial has yet shown a biological-age benefit.

That is enough to justify continued research. It is not enough to say Ca-AKG reverses human aging.

What would count as stronger evidence?

The field needs randomized, placebo-controlled data showing a reproducible effect across validated clocks and, ideally, concordant changes in physiological outcomes such as vascular function, muscle performance or metabolic health.

Even then, a methylation-age improvement would still be a biomarker result. Demonstrating fewer age-related diseases or longer human lifespan is a much higher evidentiary bar.

Bottom line

The Ca-AKG biological-age story is interesting, but the current human evidence remains observational.

The original “eight years younger” result came from a small uncontrolled Rejuvant cohort. The much larger 2026 study found a smaller 1.8-year cross-sectional association for delayed-release AKG, while its adjusted longitudinal signal was not significant. ABLE is designed to provide the randomized evidence the field needs, but published outcome data are not yet available in our audited corpus.

Until randomized results exist, describe Ca-AKG as associated with lower DNA methylation age in some delayed-release observational datasets — not as proven to reverse aging.

For the wider evidence, return to the Ca-AKG pillar. For formulation and dose implications, see Ca-AKG dosage and the Ca-AKG buying guide.