This is a small human randomized controlled trial, not a mouse study. In it, a rosemary, ashwagandha and luteolin blend called PB125 improved a key marker of artery function in older adults after just two weeks. Then it helped stop that marker from sliding during five days of enforced bed rest. The details matter, so here is what the study did and did not show.
What is PB125, exactly?
PB125 is a botanical Nrf2 activator. Nrf2 (nuclear factor erythroid 2-related factor 2) is a master switch for the body's own antioxidant defences. The blend combines three plant-derived ingredients:
- Rosemary (carnosol and carnosic acid)
- Ashwagandha (withaferin A)
- Luteolin
This is the formula sold commercially as Protandim NRF2 Synergizer. The research team's premise is that aging and physical inactivity both contribute to cardiovascular disease, partly through endothelial dysfunction linked to weakened Nrf2 signalling. The endothelium is the thin lining of your blood vessels. If you can nudge Nrf2 back up, the vessels might work better.
How the trial was built
The study, led by Carlini and colleagues at the University of Utah and the Salt Lake City VA, was published in Free Radical Biology and Medicine in 2026. It was double-blind, randomized and placebo-controlled.
- Participants: 20 younger adults (8 men, 12 women, average age 27 ± 7) and 24 older adults (12 men, 12 women, average age 67 ± 8)
- Intervention: PB125 at 200 mg/day or placebo
- Three visits: baseline, after 2 weeks of supplementation, and after a disuse challenge
- Disuse challenge: 5 days of bed rest for older adults, or 2 weeks of limb immobilization for younger adults
- Measures: brachial (arm) and popliteal (leg) artery flow-mediated dilation (FMD), passive leg movement-induced leg blood flow and vascular conductance, and serum superoxide dismutase (SOD), an antioxidant enzyme
FMD is a standard, non-invasive test of how well an artery widens in response to increased blood flow. Higher generally means healthier endothelial function.
The headline result: older arteries responded in two weeks
In older adults, two weeks of PB125 raised brachial FMD from 2.8 ± 1.5% to 3.8 ± 1.3% (p < 0.0001). Popliteal FMD rose from 1.5 ± 1.5% to 2.3 ± 1.4% (p = 0.033). Both increases were reported relative to placebo.
Younger adults saw no such gain. FMD did not change significantly with PB125 at this stage (both p > 0.27). That fits the idea that the supplement helps most where Nrf2 signalling is impaired, though the study can't prove that mechanism. Younger people likely already have healthy endothelial function, which leaves little room to improve.
The bed rest twist: protection, not just improvement
Bed rest is a harsh model of what happens during hospitalization or injury. Here the older adults on PB125 largely held their ground, compared with placebo (all p < 0.05):
- Brachial FMD: 3.8 ± 1.3% to 3.6 ± 1.4% (p = 0.543, no significant drop)
- Popliteal FMD: 2.3 ± 1.4% to 2.7 ± 1.4% (p = 0.269)
- Leg vascular conductance: 1.1 ± 0.8 to 1.1 ± 1.5 (AUC, p = 0.530)
- Circulating SOD: 28.3 ± 7.2 to 28.6 ± 8.6 U/mL (p = 0.888)
The abstract doesn't give the placebo group's numbers, but the between-group comparison was significant. That implies the placebo group's vascular function declined or fared worse. The paper's framing is that PB125 preserved vascular function and antioxidant capacity.
Young adults: a narrower benefit
Following two weeks of limb immobilization, younger adults on PB125 preserved popliteal FMD (4.4 ± 2.8% to 3.4 ± 1.8%, p = 0.302 within the group) compared with placebo (p < 0.05). So even without a baseline FMD gain, the blend appeared protective against disuse-related decline in the immobilized limb. Note that the within-group change was a numerical drop that didn't reach significance. The paper's claim rests on the comparison with placebo.
Limitations you should know
- Small sample. 44 people total, split across two age groups and two arms, so each arm is small. Results can look cleaner in small trials than they prove to be in larger ones.
- Surrogate outcomes. FMD and blood flow are markers of vascular function. The study did not measure heart attacks, strokes or any clinical events.
- Short duration. Two weeks of supplementation tells us nothing about long-term benefit or safety.
- Different disuse models. Older adults had bed rest and younger adults had limb immobilization, so the age groups can't be compared directly.
- Narrow population. The participants were presumably screened volunteers, and the abstract doesn't describe them as having cardiovascular disease. Results may not carry over to patients.
- Single study. It needs replication by independent groups. The authors declared no conflicts of interest, which is reassuring, but it remains one trial.
Practical takeaways
Dose studied: 200 mg/day of PB125. The abstract doesn't specify timing, such as morning versus evening or with food, so there's no evidence-based answer on that. Don't assume other rosemary, ashwagandha or luteolin products match this formulation or dose.
Who might be interested: Adults around age 60 and above who are curious about vascular aging, or who face a period of reduced mobility, such as a planned surgery or recovery. In this trial, those are the groups where effects appeared. Anyone in that position should talk to their clinician first rather than using a supplement as a substitute for movement, rehab or prescribed therapy.
Who probably doesn't need it: Healthy younger adults showed no baseline FMD improvement, so there is no evidence of benefit for them outside an immobilization scenario.
Who should be cautious or skip it: This is general guidance, not from the paper. People who are pregnant or breastfeeding, have thyroid or liver conditions, take immunosuppressants, sedatives or thyroid medication, or take blood pressure or diabetes drugs should consult a clinician first. Ashwagandha in particular carries such cautions.
The bottom line
This trial is an encouraging, well-designed proof of concept that targeting Nrf2 in humans can improve and protect endothelial function. It is not proof that PB125 prevents heart disease or speeds recovery from hospital stays. Larger and longer trials with clinical endpoints are the necessary next step.
