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Serum After Fermented Whey Grew Lab Muscle Cells More Than Regular Whey

Serum drawn after men drank fermented whey made lab-grown muscle cells larger than serum drawn after regular whey.

By Dr. Josh Axe · November 3, 2026 · 1 source · Watch

Photo: Pexels

At a glance

Who was studied: Young and older men.

Blood serum collected from men after they drank fermented whey protein, then added to cultures of lab-grown mouse muscle cells (C2C12 myotubes), made the cells grow larger than serum collected after conventional whey, according to a randomized crossover study published October 23, 2026 in Experimental Gerontology.

Young and older men drank a fermented whey protein drink and, on a separate occasion, a conventional non-fermented whey drink, in a randomized, double-blind crossover design. After each drink, researchers collected blood and added the serum, at 10% of the culture medium, to C2C12 myotubes, mouse-derived muscle cells grown in a dish.

Serum collected after fermented whey increased muscle cell diameter compared with serum after conventional whey, with no difference between age groups on that measure. For muscle protein synthesis, the process of building new muscle protein, the effect depended on age: post-fermented-whey serum from older men produced more protein synthesis in the cells than serum from younger men. Serum after fermented whey also raised activation of S6K1, a growth-signaling protein, and of signaling molecules tied to how cells burn fuel, compared with serum after conventional whey.

The authors said the findings may provide mechanistic insight for nutrition strategies against anabolic resistance, the reduced ability of aging muscle to respond to protein, and for improving muscle energy metabolism.

10% postprandial human serum

Share of the culture medium made up of serum collected after men drank fermented or conventional whey, applied to lab-grown muscle cells

Experimental Gerontology, 2026, Uemichi et al.

This tested human blood serum on mouse muscle cells in a dish, not muscle growth in the body, so it cannot show whether eating fermented whey builds more muscle in people. Sample size and exact numbers were not reported in the abstract, and whether adults with reduced muscle mass would see the same effect is untested.

Dr. Axe’s Take

I love that the strongest protein-building response here came from older men's blood, because anabolic resistance is a big reason people lose strength as they age. This study is a reminder that the form protein comes in can change the signal your muscle cells get, not just the grams on the label. This week, I'd spread quality protein from whole foods across every meal and pair it with resistance training, since muscle only grows when protein meets a reason to rebuild.

— Dr. Axe

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Story summary

Who: Young and older men; exact sample size not reported in the abstract
Design: Randomized, double-blind, active-controlled crossover trial; serum applied to C2C12 mouse myotubes in a dish
Dose: Fermented whey protein vs conventional non-fermented whey protein, consumed on separate occasions
Primary result: Serum after fermented whey increased myotube diameter versus serum after regular whey; no age difference on that measure
Secondary: Muscle protein synthesis was higher with older men's post-fermented-whey serum than younger men's; S6K1 and oxidative metabolism signaling both increased with fermented whey serum
Funding / conflicts: Funder listed in the journal record: Japan Society for the Promotion of Science. Competing interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Date: Oct 23, 2026