What circulating stem cells are, in plain terms

Before looking at the study, it helps to be clear about what was actually being counted, because the phrase "stem cells" carries a lot of assumptions that this research does not support.

Stem cells are the body's unspecialised repair cells. Unlike a skin cell or a muscle cell, which already has a fixed job, a stem cell can renew itself and, under the right signals, mature into other cell types. Most of them sit quietly inside tissue such as bone marrow. A smaller number circulate in the bloodstream at any given moment, and it is that circulating fraction, not the whole reserve, that the 2019 study looked at. If you want the full plain-language version of what these cells are and how they behave, we wrote a separate primer on what stem cells are.

Two details matter for reading this study honestly. First, the number of stem-like cells moving through your blood naturally rises and falls through the day and in response to things like exercise and injury, so a short-term change in that number is not the same as changing the body's total supply. Second, that circulating activity is understood to decline with age, which is part of why the topic draws research interest in the first place. Neither point means a berry extract reverses anything. They simply frame what a two-hour measurement can and cannot tell you.

What the 2019 study measured, step by step

The 2019 study, published and indexed in PubMed Central as PMC6368418, looked at whether a sea buckthorn berry phytochemical extract, abbreviated SBB-PE, could change the level of a specific circulating cell population in human blood over a short window of time. Here is how it worked, in order.

1. Two groups. Participants either received the SBB-PE extract or a placebo, so any change could be compared against a baseline of people who took nothing active.
2. Two markers. Researchers identified the cells of interest using two surface markers, CD45 and CD90. CD90 is associated with certain stem-like and progenitor cells; CD45 is found on most white blood cells. Cells that are CD45-negative or only dimly CD45-positive, while still carrying CD90, are used as one way to flag a circulating population with stem-like characteristics. The two populations tracked were labelled CD45-/CD90+ and CD45dim/CD90+.
3. Three blood draws. Blood was taken at baseline (before dosing), at one hour, and at two hours.
4. Change from each person's own baseline. Rather than compare people against each other, researchers calculated the percent change from every participant's own starting point at each time. This is the standard way to control for the wide natural variation from one person to the next.

In other words, the study did not weigh a total stem cell reserve or track healing. It counted how a narrow, marker-defined population of circulating cells moved over 120 minutes, in people who had taken either the extract or a placebo.

What the results showed

By two hours, the SBB-PE group's percent change in CD45-/CD90+ and CD45dim/CD90+ markers had risen clearly above baseline, following a steady upward trend from the one-hour mark onward. The placebo group showed the opposite pattern: readings stayed close to flat, and by two hours had drifted slightly below their own starting point rather than rising.

Two features of that pattern are worth naming. It was rapid, appearing within a two-hour window rather than over days or weeks, and it was selective, showing up in the marker-defined population the researchers were tracking rather than as a broad, non-specific shift. A selective change is generally more interesting to researchers than a vague one, because it is easier to connect to a specific biological signal. That is a reason to keep studying it, not proof of what causes it.

The researchers reported the two-hour between-group difference as a statistical trend, commonly written as P<0.1, rather than meeting the more conventional P<0.05 threshold for statistical significance. That distinction matters. A trend-level result means the pattern is suggestive and worth further study, but it carries less statistical confidence than a result that clears the stricter bar, and honest reporting keeps that distinction visible rather than rounding it up to "proven."

What the results mean, and what they do not

It is worth being precise about the boundaries of a single, small, trend-level finding. Read carefully, the result is genuinely specific. Read loosely, it is easy to turn into a claim the data never made.

• The study measured a short-term (two-hour) shift in specific circulating cell surface markers, not a lasting increase in the body's total stem cell supply, and not tissue repair outcomes.
• The extract used, SBB-PE, is a concentrated phytochemical preparation from the sea buckthorn berry. It is not the same thing as a whole-food puree made from the entire berry, and its concentration, processing and composition differ from a food product.
• The result was reported at trend-level statistical significance, not the stronger conventional threshold, in what appears to be a single study rather than a body of replicated evidence.
• The study does not claim, and this article does not claim, that the extract or any sea buckthorn product treats, cures or prevents any disease.

So what does it mean? At most, it means that in one small human trial, a concentrated sea buckthorn extract was associated with a fast, marker-specific movement in a circulating cell population, and that the pattern is worth another, larger, more rigorous look. What it does not mean is that drinking sea buckthorn, in any form, has been shown to raise your stem cells, slow ageing, or do anything to a health condition. Holding both of those statements at once is what honest reading of a preliminary study looks like.

How sea buckthorn compares to other things studied

People often ask how this fits alongside the more familiar ways stem cell activity gets discussed. It helps to separate three very different categories.

Clinical stem cell procedures, such as bone marrow transplants or injected cell therapies, are medical interventions that physically add or mobilise cells under clinical supervision. They are a different universe from a berry extract, and we compare the two approaches directly in our piece on natural versus injected stem cell approaches. Nothing in the 2019 study puts sea buckthorn in that category.

Exercise and lifestyle are among the most consistently studied everyday influences on circulating stem-like cells, and physical activity in particular has been observed to move these populations. Set against that backdrop, a food-derived extract showing any measurable, selective movement is what makes the finding notable enough to report, while also being a reminder that a short marker change is not unique to any one input.

Plant compounds are where sea buckthorn actually sits. The research interest is in the berry's specific phytochemistry rather than the fruit as a whole, and we go through the individual candidates in which sea buckthorn compounds are being studied. One family that draws particular attention is its unusual fatty acid profile, including the rare omega-7, which we cover in the omega-7 explainer. The honest summary is that sea buckthorn is an interesting plant to study here, not a proven one.

Why this berry, specifically

Sea buckthorn is not a garden berry. The wild plant studied for compounds like this grows at high altitude on the Tibetan Plateau and across Inner Mongolia, often above 3,000 meters, in conditions of intense UV exposure and extreme temperature swings that a backyard shrub never has to survive. Plants under that kind of stress tend to build a denser, more varied chemistry to protect themselves, and that chemistry is part of why researchers keep returning to this particular berry when studying plant phytochemicals.

That context is about where the fruit comes from and why it is worth a scientist's attention. It is not a claim about what the fruit does inside the human body. A berry can be genuinely remarkable as a plant and still owe you no health outcome, and keeping those two ideas separate is the whole point of reading a study like this one carefully.

For the compounds researchers believe may be driving findings like this one, see which compounds in sea buckthorn are being studied. For the general biology behind why circulating stem cell activity matters at all, start with what are stem cells, then read why that activity declines with age.

This article is educational content, not medical advice. It does not diagnose, treat, cure or prevent any disease. Speak with a qualified healthcare provider about your own health decisions.