Dr K has made reference to testing grass-fed butters for Vit K2 levels and has said that Kerrygold tested at zero before, which didn't help with some people's suspicions that KG may not be entirely grass fed. But tartare provided a link to a fact sheet advertisement in which Kerrygold proclaims in crystal clear verbiage that their "Cows are entirely grass-fed" and goes into much more detail. Also, sarah-ann, a long time PaleoHacker, says she lives an hour away from where the KG cows are pastured and the grass is super green.
So then I wonder... does the potency of Vitamin K2 diminish with time? If so, how long do we have before the value becomes reduced too much?
I wonder if the K2 doesn't vary wildly with season. I know that the butter is different colours depending on the time of year. Hence why high vitamin butter oil is only from cows fed on summer pasture.
I have read some data that high levels of vitamin A and D can deplete vitamin k levels. That was not in humans but I follow k2 data closely. I think high levels of vitamin are problematic for many reasons
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