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| Image 1: Who would have thought that this piece of goose liver pate contains a natural test-booster? Unfortunately even this SuperFood won't give you your 1g /day. |
Can you imagine how it must feel to be the shrinking violet in a family of nutritional saviours? Where your brothers C, E, not to mention the rising superstar D, get all the attention and you are treated just like another letter in the vitamin ABC? Well, I guess you don't ... but if vitamins had feelings,
menaquinone, also known as
Vitamin K2, certainly would ;-) After all, even many supplement junkies know it only as "that strange co-factor of vitamin D. In part this may even be my fault. After all, I have discarded all the previous studies on its beneficial effects on heart health (
Galeijnse. 2004), bone formation (
Yamaguchi. 2001) and resorption (
Yamaguchi. 2003) and so-on and so-forth, as not "sexy" enough to make it into the SuppVersity news. The results of a recent study, by Asagi Ito et al. (
Asagi. 2011), on the other hand, are sexy, there is no doubt about it ;-)
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| Image 2: Don't be fooled by the soy industry - there is exactly ZERO MK4 in Natto! You will have to resort to "real" foods if you want some MK-4 in your diet - cf. figure 4, below; unfortunately even goose liver, the dietary source with the greatest amount of menaquinone (MK4) won't give you enough to see results. |
Did you know that there are thousands of forms of "vitamin K"? The major ones are yet
phylloquinone, also known as vitamin K1, which is
abundant in all sorts of green vegetables (>200g/100g), has a pretty low bioavailability of <10% and is important for normal blood coagulation aside, and a certain form of
menaquinone that has been labeled MK-4. Only recently have scientists discovered that the latter is synthesized from phylloquinone or menanquinones with longer side-chains in certain mammalian tissues (
Suttie. 2011). This ability to produce MK-4 from dietary substrates and the
high MK-4 content in human brains and reproductive organs speaks for the importance of this hitherto largely overlooked "vitamin" (in the strict sense it is no vitamin if your body can produce it on its own).
The Japanese scientists treated a group of Male Wistar rats on a standard diet with 75mg/kg body weight of vitamin K2 (menaquinone-4;
human equivalent 12mg/kg, 972mg for an 80kg adult) for 5 weeks and measured their plasma and testes levels of testosterone... and the results, were "sexy", as you can see in figure 1 ;-)
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| Figure 1: Serum testosterone levels (in ng/dl) in male Wistar rats in the course of five weeks on 75mg/kg MK4 vs. control (data adapted from Asagi. 2011) |
As the data goes to show there was - despite the usual diurnal ups-and-downs a clear trend towards increased serum testosterone levels in the MK-4 group - on average, +56% more testosterone from weeks 1-5 in the MK4 group. And a whopping +70% at the end of the study period. An
even greater increase of +88% was seen in the tissue concentration of testosterone within the testes. The latter went hand in hand with a profound enrichment in vitamin K2 content in the reproductive organs, as well as in the livers of the MK4-supplemented animals (no, I did not make a mistake, there really was almost no MK4 in the livers of unsupplemented animals, cf. figure 2).
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| Figure 2: MK4 levels (pmol/g tissue) in liver and testes of rats after 5 weeks on 75mg/kg supplemental menaquinone-4 (data adapted from Asagi. 2011) |
Interestingly, these profound increases in testosterone production were
not mediated by changes in luteinizing hormone concentration.
From the rat model to the petri-dish: Exploring the underlying mechanism
In in-vitro studies, the scientists also found that vitamin K1 was without effect on testicular I-10 cells, and that
Warfarine,
a pharmacological anticoagulant did not suppress the
dose-depend (cf. figure 3) testosterone boosting effects of MK4 on a cellular level.
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| Figure 3: Relative increase in testosterone production of testicular I-10 cells after 24h of incubation with different amounts of MK4 (data calculated based on Asagi. 2011) |
The most likely explanation, according to Asagi et al., for the profound effects MK4 has on the
output (its like an after-burner for your testes ;-) of testosterone would be
c-AMP mediated, as
treatment of I-10 cells with MK-4 in the presence of db-cAMP was found to significantly enhance testosterone secretion into the cul-ture medium, and the maximum enhancement of secretion was observed when 30μM MK-4 was present in the medium.
That being said, I bet your next question is
"where can I get that stuff"? Well, the most obvious answer would be: At the supplement vendor of your choice, which is basically where the scientists got their MK-4 (Nisshin Pharma Inc.), as well.
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| Figure 4: MK4-content (µg/100g) of the only significant (~10µg/100g or more) dietary sources of MK4 (data based on Schurgers. 2000) |
If you look at the
only "reasonable" (i.e. foodstuff with 10µg or more MK-4 per 100g) dietary MK-4 sources I have compiled for you in figure 4, you will probably also understand, why the rats had almost ZERO MK-4 in their livers and MK-4 was not even detectable in the serum of the 6 healthy male volunteers whose serum Schurgers and Vermeers as part of their analysis of the plasma vitamin K response to different foodstuff (
Schurgers. 2000). Since
the scientists focused on K1 and MK-7 (the "Natto-K2") the rest of their results, i.e. everything but their analysis of 13 types of meat, 6 types of fish, 9 types of fruits and vegetables, 10 types of dairy, egg products, oils, breads, and beverages (the only relevant sources are listed in figure 4) are unfortunately
useless for us.... anyway, if you want to build some muscle, you better go now and
enjoy a few kilo of the good old goose liver paste, although
even that would not give you the 1g "human equivalent" of the 75mg/kg the rats in the study received.
