Muscle hypertrophy from blood: 0 people in a loud preprint about a new supplement.

Muscle hypertrophy — the growth of muscles — is what half of sports nutrition is sold for. A new preprint promises another pathway to it: haemoglobin hydrolysate, which supposedly directly triggers muscle growth. It sounds like a breakthrough. But muscle hypertrophy is shown here in fish, mice, and cells in a test tube — there are no humans in the study.

Let's break down what the authors actually found, why the mechanism is interesting, and why this discovery is still a very long way from the supplements shelf.

What is globin digest and where did it come from

Globin digest (GD) is a haemoglobin hydrolysate, meaning blood protein broken down into small peptides by enzymes. It has previously been studied as an anti-obesity and glucose-control agent. Its anabolic potential - the ability to build muscle - has not yet been explored.

The authors of the preprint from Mie University decided to test exactly this. Can the split blood protein not just nourish muscle as a source of amino acids, but trigger its growth as a signal.

The difference here is fundamental. The body breaks down ordinary protein from food into its component parts and uses them as building material. A signalling molecule, however, works differently: it's not building material, but a «grow» command that the cell reads and uses to activate its own programmes. If a haemoglobin hydrolysate genuinely worked as a command, it would be a new class of sports nutrition, not just another protein.

The question was well-posed. The answer they received is also interesting - but with big asterisks.

The study showed the following about muscle hypertrophy

The experiment proceeded on three levels. Adult zebrafish were given GD at 400 mg/kg per day for a week – and their swimming distance significantly increased. Mice were given 1 g/kg per day for four weeks – and both grip strength and endurance in the rotarod test increased.

The most compelling figure is in the tissue. The diameter of muscle fibres in mice increased 1.5-fold. Expression of the fast fibre genes Myh1 and Myh2 rose 1.9-fold and 1.8-fold respectively. This is muscle hypertrophy at a molecular level.

The detail about fast-twitch fibres is not accidental. It is precisely these fibres that are responsible for explosive strength and are most affected by age in sarcopenia. Therefore, if the effect is ever confirmed in humans, it will be most interesting for specific groups. These are primarily older people and those recovering from injuries – these are the ones who lose fast-twitch fibres.

It all started with the simplest model. Adult GD zebrafish were also given it, and they started swimming noticeably further within a week. It might seem, what does a fish have to do with it. But such a progression from a simpler organism to a more complex one is a standard way to test a mechanism before moving on to mammals.

In muscle cells in a test tube, GD dose-dependently (from 1 to 100 µg/ml) enhanced the maturation and accumulation of contractile protein. That is, the effect was reproduced in an isolated system, without the involvement of the whole organism.

It is worth noting the honesty of the authors themselves. They do not present GD as a ready-made substitute for protein, but directly write that it is a «foundation» for future precise sports nutrition. That is, the claim is more modest than the headlines that are generated around it. The problem is not with the researchers, but with how a cautious scientific result is transformed into a loud «new supplement builds muscle» on its way to the reader.

Why the mechanism is interesting: peptide relay

The most unusual thing is how exactly GD works. It’s not just nitrogen fuel for the muscle. The authors show that it is a signalling modulator with «relay» logic.

Of the six identified peptides, two (WTQR and WGK) trigger the early stage – switching on the growth initiator genes MyoD and Myf5. The other two (VVYP and FES) accelerate the middle stage of maturation.

This is an important detail for understanding the novelty. Usually, a protein supplement is assessed by quantity – how many grams, how many amino acids. Here, what matters is not the mass, but the specific sequence of short fragments and the order in which they act. If the relay metaphor proves correct, it changes the logic of sports nutrition. Not «more protein,» but «the right peptides at the right time.».

This step-by-step synergy resulted in stronger muscle hypertrophy than each peptide individually. The relay worked better than individual runners – this is the novelty of the work.

If the effect is confirmed, the logic of the relay operation explains a lot. The whole hydrolysate worked better than individual peptides because different fragments pick up the process at different stages – like links in a single conveyor belt. This is an elegant hypothesis about how short peptides can stimulate muscle growth without additional protein. But the word «hypothesis» is key here – everything is shown in simplified models, far removed from the body of an adult performing weightlifting.

Great stars: why it's not about people yet

Now for the awkward part, without which the first three paragraphs are meaningless.

First of all, this is a preprint. It has not been peer-reviewed – work is posted on bioRxiv before colleagues have checked it. The reliability of such a source, according to our scale, is 8 out of 10, and that's taking into account the lack of review.

Secondly, there isn't a single human in the study. Fish, mice, cell culture. The path from «it worked on mice» to «it will work on humans» is littered with drugs that didn't make it. Muscle hypertrophy in a rodent does not equal hypertrophy in someone who goes to the gym. A mouse's metabolism, its size, and its reaction to peptides are different. Dosages aren't directly transferable either. What works per gram per kilogram in a mouse doesn't mean the same regimen for a human.

Thirdly, there's a conflict of interest. Two of the co-authors work for the pharmaceutical companies Rohto Pharmaceutical and MG Pharma. This isn't a death sentence for the research, but it is a reason to read claims about the product's benefits particularly carefully.

None of these points imply that the work is bad. Preprints are a normal part of science, animal research is a mandatory step before human trials, and industrial funding exists in legitimate work too. The problem arises when such work is presented to the public as a finalised conclusion: «the supplement works». Between «it worked on mice in a lab with pharmaceutical funding» and «it's worth buying» lie several years of checks, which haven't happened yet.

How does that fit with what we already know about the protein?

It's worth mentioning the basics here. For actual muscle hypertrophy in humans, the evidence base has long been known: sufficient protein plus strength training. How much protein exactly – we discussed in detail in a separate article about The norm and optimum of protein consumption.

Haemoglobin hydrolysate against this background is not a replacement, but a hypothesis. Perhaps one day it will become a niche tool, for example, for people with muscle loss. Perhaps the effect will not be reproducible in humans at all. And for those over 50, the question of priorities is even sharper. What is more important for a muscle with age, we discussed in a post about Strength training versus protein after 50.

No new molecule overrides basic mechanics: to grow muscle, you need load and building material. A supplement can be an addition, but not a replacement.

It is also worth remembering the economics of the matter. As long as there is no human data, there is no way to say what dose, form, and duration of intake would be effective. All the figures from the preprint are doses for mice, recalculated for body weight. They cannot be directly transferred to humans, and therefore it is impossible to calculate how much a real supplement with proven efficacy would cost. This is another reason not to rush: even if the product existed, no one knows its parameters today.

Muscle hypertrophy in practice: what should the reader do

The practical conclusion is brief. There's no reason to rush to get hemoglobin hydrolysate – there's currently no product with a proven effect on humans; there's an interesting signal in animals.

It is worth keeping an eye on the topic, but not changing anything in your diet because of a single preprint. If the goal is muscle hypertrophy, proven levers work, not fresh headlines.

This is one of those cases where the correct reaction to «scientists have found» is simple. Don't rush to buy, but wait for reviews and human studies.

It's useful to have a simple filter for such news. The first question is, who is it shown to be effective in: people, animals, or cells. The second is, has the work undergone peer review. The third is, who funded it. If the answers are «in mice,» «no,» and «the manufacturer,» then it's a reason to be interested, not to change behaviour. This preprint provides exactly that set of answers, and that's normal for early science. It would be abnormal to present it as an instruction for action.

Conclusion in one sentence

Haemoglobin hydrolysate does indeed stimulate muscle hypertrophy through a direct growth signal – but so far, only in fish, mice, and cells. For humans, this is a promising hypothesis, not a ready-made supplement.

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Sources

• Nakai M, Zang L, Fukada K, Ishido K, Nishimura N, Shimada Y. Globin digest and its constituent peptides promote skeletal muscle hypertrophy and enhance physical performance. bioRxiv. 2026. DOI: 10.64898/2026.05.27.728339
• Morton RW, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. Br J Sports Med. 2018. DOI: https://doi.org/10.1136/bjsports-2017-097608