Does Diluting Old Blood Work Like Raising Ore Grade? A Mining Analogy for Plasma Exchange, Rated 45 Percent

Replace half the plasma of an old mouse with salt water and albumin, and several tissues start acting younger. No young blood is needed. Clinics now offer plasma exchange as a longevity service, so the reason it works is not an academic question.

Our research desk borrows an idea from mining. Every ore body has a grade, the share of useful metal per tonne of rock. Below a threshold grade, processing costs more than it returns.

The desk argues that old plasma is low-grade ore. Aging cells release a stream of proteins carrying less useful signal and more junk. Receptors, protein-disposal systems and immune surveillance spend their limited capacity processing that junk. Dilution lifts the overall grade back above the threshold where tissues can work.

The prediction is a specific curve. In 20-month-old mice, diluting plasma by 25 percent should help a little, 50 percent a lot, and 75 percent no more or even harm. That last step reflects needed factors, such as clotting proteins and hormones, falling too low.

The desk gives this 45 percent odds.

The founding experiment is real but misattributed. Our desk credited it to Conlon and colleagues in 2023. The saline-albumin dilution study is by Mehdipour and colleagues in the Conboy lab, published in Aging in 2020.

In that study, one exchange of half the plasma improved muscle repair, reduced liver fat and fibrosis, and increased new neuron formation in the hippocampus of old mice. The authors' own explanation is close to the desk's: diluting many selfregulating proteins resets the blood's signaling network. The added albumin did not appear to be the sole driver.

Human results are early and split. A Buck Institute trial in Aging Cell in 2025 randomized 42 healthy adults over 50 to plasma exchange regimens or placebo. Fifteen epigenetic clocks improved versus placebo, most with exchange plus immunoglobulin infusion.

A Czech crossover trial in Scientific Reports in 2025 tested repeated plasma donation without albumin replacement. It found no epigenetic rejuvenation. Several clocks, including GrimAge and DunedinPACE, moved in the older direction.

Those two results fit the desk's frame in one way: what is put back may matter as much as what is removed. But neither trial tested a dose curve.

If benefit comes from a threshold, the goal is the right amount of dilution at the right interval, not a hunt for one villain molecule. If a short list of proteins explains most of the effect, targeted drugs could replace an invasive procedure. Either answer would guide a field moving faster than its evidence.

• Treat plasma exchange for longevity as experimental; the human data are small and short-term. • If you are considering it, prefer a registered trial with safety monitoring over a cash clinic. • Know that plasma exchange carries real risks, including line infections, bleeding and low blood pressure. • Anyone on blood thinners or with heart disease should discuss it with their physician first.

The desk names the weak link itself. If three or four proteins, such as TGF-beta family members, explain most of the benefit, the ore-grade picture is decoration. Its predicted plateau at 50 percent would also fail if benefit rises steadily with dilution.

• A mouse study testing 25, 50 and 75 percent dilution side by side. • Larger, longer human plasma exchange trials with functional outcomes, not just clocks. • Whether removing a named handful of proteins reproduces the full dilution effect.