“Natural” sounds like the safest word on a supplement label. It gives a sense of security to people purchasing the supplements. For vitamin K2, it can be tricky, though, it isn’t really telling you what most people assume it’s telling you. The most popular form of K2, called MK-7, can exist in two different shapes and only one of them provides benefits once it’s inside your body.
Whether a product is useful or not has almost nothing to do with whether the label says “natural,” “fermented,” or “natto-derived.” It comes down to something far less visible that how carefully the manufacturing process was controlled.
The Same Molecule, Two Different Shapes
Think of MK-7 (a form of vitamin K2) like a key that needs the correct shape to fit and work in a lock.
MK-7 has a main structure (the core) with a long tail attached to it. This tail can arrange itself in two different ways:
- All-trans form: The tail stays straight and stretched out, like a zipper lying flat. This is the active form because the body can recognize and use it properly.
- Cis form: The tail bends or twists, like a zipper that has become slightly curled. Although it looks almost the same chemically, its shape is different, so the body cannot use it effectively.
When vitamin K enters the body, it helps activate certain proteins that are important for functions like calcium regulation and bone health. In a 2022 study, researchers tested these two forms of MK-7 separately to see how well they could activate a vitamin K–dependent protein.
The results were clear:
- The all-trans MK-7 successfully activated the protein.
- The cis MK-7 showed very little activity.
This study was important because it proved that even though two forms of MK-7 may look the same on a product label, their biological effects can be completely different. The shape of the molecule matters, just like two keys that look similar but only one can actually open a lock. (Cirilli et al., 2022)
What Happened When Scientists Tested Store-Bought Supplements
The problem with MK-7 quality is not limited to laboratory experiments, it can also happen in real supplements that people buy and consume.
In a study, Polish researchers collected different vitamin K2 (MK-7) supplements available in the market and analyzed them to check how much of the product was actually the useful all-trans form (Szterk et al., 2018).
The results were surprising:
- Many supplements contained less active MK-7 than the amount mentioned on their labels.
- One supplement from the U.S. did not contain any detectable MK-7 at all, even though the label claimed it did.
- Some supplements also contained cis-MK-7 impurities, which are less useful because the body cannot effectively use them.
Interestingly, even a supplement that claimed to be made from natural natto extract (a fermented soybean product naturally rich in vitamin K2) was not completely free from this problem. This showed that simply using a natural source does not automatically guarantee high purity or a fully active product.
In simple words, two supplements may both say “MK-7” on the bottle, but the actual amount of active, usable vitamin K2 can be very different. The source of MK-7 alone does not determine quality but the purity and chemical form are what matter. (Szterk et al., 2018)
Why “Naturally Fermented” Doesn’t Automatically Solve This
Fermentation is often considered a natural solution because certain bacteria naturally produce the active trans-MK-7 form of vitamin K2. However, fermentation quality depends greatly on how the process is managed.
Fermentation is not simply a matter of adding bacteria and waiting. The bacteria need the right conditions, including the correct balance of nutrients in the fermentation mixture (called the fermentation broth). If the conditions are not optimized, the bacteria may produce less of the useful trans-MK-7 form and more of the unwanted cis form.
A 2022 study tested different nutrient combinations used during MK-7 fermentation and found that the fermentation recipe made a huge difference (Lal et al., 2022).
The researchers found that a carefully optimized nutrient mixture produced over 12 times more active trans-MK-7 while generating nearly three times less inactive cis-MK-7 compared to a poorly optimized fermentation process.
This shows that the label “naturally fermented” does not always guarantee the same quality. Two supplements may both come from bacterial fermentation and both be called “natural,” but their effectiveness can be very different depending on how carefully the fermentation process was controlled.
In simple terms, the bacteria are only part of the story and the environment in which they grow determines how much useful MK-7 they produce. A well-controlled fermentation creates a cleaner, more active product, while a poorly controlled one may contain less beneficial MK-7 and more unwanted forms. (Lal et al., 2022).
What Actually Determines Whether K2 Works
Purity and process control matter far more than the word “natural” on its own. It also helps to get the basic form right in the first place. Separate research comparing K2 types found that MK-7 stays active in the bloodstream for up to 48 hours after a single dose, while the shorter MK-4 form wasn’t detectable at any point measured (Sato et al., 2012).
So, there are really two questions worth asking about any K2 product:
- Is it the MK-7 form?
- Was it made in a way that keeps it mostly all-trans?
“Natural” answers neither one.
Where TerraQuino Comes In
TerraQuino produces MK-7 through a controlled fermentation process built around consistent isomer purity, delivering long-chain, allergen-free vitamin K2-7.
It’s formulated for tablets, capsules, softgels, sachets, and liquids, with the kind of process control that the research above suggests actually determines whether a K2 ingredient performs the way a label implies. TerraQuino doesn’t just rely on the word “natural” to make that case as the manufacturing process is the actual answer.
Frequently Asked Questions
Does “fermented” or “natural” on a label guarantee good-quality K2?
No. Testing of real supplements found cis-form impurities even in a product labeled as natural natto extract (Szterk et al., 2018). The label alone doesn’t confirm purity.
How would I know if a K2 supplement is mostly the useful, trans form?
Most consumer labels don’t break this down, since standard testing methods don’t always separate cis from trans MK-7. Buyers largely have to rely on the manufacturer’s own quality controls and third-party testing rather than the label wording.
Is synthetic K2 automatically worse than natural K2?
Not automatically, the research shows the deciding factor is the isomer ratio in the final product, not simply whether it started out synthetic or fermented (Lal et al., 2022). A poorly controlled natural process can end up with more impurities than a well-controlled one.
Does this cis-versus-trans issue affect MK-4 as well as MK-7?
Most of the published research on this specific isomer problem has focused on MK-7, since it’s the form most commonly sold as a standalone supplement. MK-4 has its own separate bioavailability limitations, described in comparison studies (Sato et al., 2012).
References
Cirilli, I., Orlando, P., Silvestri, S., Marcheggiani, F., Dludla, P. V., Kaesler, N., & Tiano, L. (2022). Carboxylative efficacy of trans and cis MK7 and comparison with other vitamin K isomers. BioFactors, 48(5), 1129–1136. https://doi.org/10.1002/biof.1844
Lal, N., Seifan, M., & Berenjian, A. (2022). Optimisation of the fermentation media to enhance the production of the bioactive isomer of vitamin menaquinone-7. Bioprocess and Biosystems Engineering, 45(9), 1519–1531. https://doi.org/10.1007/s00449-022-02752-6
Sato, T., Schurgers, L. J., & Uenishi, K. (2012). Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutrition Journal, 11, Article 93. https://doi.org/10.1186/1475-2891-11-93
Szterk, A., Zmysłowski, A., & Bus, K. (2018). Identification of cis/trans isomers of menaquinone-7 in food as exemplified by dietary supplements. Food Chemistry, 243, 403–409. https://doi.org/10.1016/j.foodchem.2017.10.001
