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This is a post for science nerds researching vitamin K. TLDR; If you're feeding a diet that's 90%+ chicken, you're meeting your cat's vitamin K requirement.
I've spent several hours researching vitamin K content in food. I know many folks feel it is unnecessary if fish is not a significant part of the diet, and I know some believe there is enough K in meat to make up for it. I also know these folks have been feeding their diets for decades with no issues. However for me, I researched vitamin K in humans and feel it is an essential nutrient. I didn't want to take any chances under providing it and wanted to know, based on current research, how much K I'm feeding and whether supplementation would be necessary.
There are a variety of forms of vitamin K: K1 (mostly in vegetables), K2 (meat, cheese, and fermented foods, including food passing through the gut and fermenting by gut bacteria), and K3 (synthetic menadione). K2 takes many forms. These are labeled MKn, where n is a number based on the length of the molecule. Most websites listing "vitamin k" content in food likely use a USDA document that actually only looked for K1 and MK-4. Most K2 in meat is longer-chained molecules (so not MK-4) and is not reported in that research. One study found "chicken meat" (no specific cuts mentioned) contained 100 mcg/100g of all forms of vitamin K. Another source found chicken meat to have 600 mcg/100g K. The second source is behind a paywall, so I can't see more details than that. Likely the true value is somewhere between the two and varies based on cut, but let's do some math with the low end number.
I'm using the Pet Diet Calculator software to calculate recipes. I've got one recipe that's 49g heart, 59g thigh (both per day) and a bunch of other things. So I plugged in the vitamin K for 108 g "chicken meat" (heart + thigh, ignoring liver) and the NRC's requirement was met. Then I ran it again with only 59g of "chicken meat" in case the muscle of the heart is radically different from muscle meats commonly consumed in the West and likely to be analyzed by researchers. That brought me to 97% of the NRC's recommendations. Given that the other foods in this recipe are also using the USDA's measurements of only K1 and MK-4, it is likely that the K requirement is met.
A final note, Vermeer et. all (the 100mcg/100g in chicken study) found other meats to be much lower in K, with the exception of beef liver (112mcg/100g). So I will need to revisit this once I work on more diets. I figured I'd share my research with any other science nerds making their own cat food.
Two last fun facts on K, cooking does not diminish K content. Also, crickets (like you can buy at pet stores for reptiles) likely contain K. (That study was based on a supplemented diet, but K was not part of the supplementation. Also, I verified that most locations of Pet Supplies Plus sell the same species in that article.) The large crickets at Pet Supplies weigh about 0.2g on average, so 4 large crickets will meet a 9-lb cat's vitamin K needs.
I've spent several hours researching vitamin K content in food. I know many folks feel it is unnecessary if fish is not a significant part of the diet, and I know some believe there is enough K in meat to make up for it. I also know these folks have been feeding their diets for decades with no issues. However for me, I researched vitamin K in humans and feel it is an essential nutrient. I didn't want to take any chances under providing it and wanted to know, based on current research, how much K I'm feeding and whether supplementation would be necessary.
There are a variety of forms of vitamin K: K1 (mostly in vegetables), K2 (meat, cheese, and fermented foods, including food passing through the gut and fermenting by gut bacteria), and K3 (synthetic menadione). K2 takes many forms. These are labeled MKn, where n is a number based on the length of the molecule. Most websites listing "vitamin k" content in food likely use a USDA document that actually only looked for K1 and MK-4. Most K2 in meat is longer-chained molecules (so not MK-4) and is not reported in that research. One study found "chicken meat" (no specific cuts mentioned) contained 100 mcg/100g of all forms of vitamin K. Another source found chicken meat to have 600 mcg/100g K. The second source is behind a paywall, so I can't see more details than that. Likely the true value is somewhere between the two and varies based on cut, but let's do some math with the low end number.
I'm using the Pet Diet Calculator software to calculate recipes. I've got one recipe that's 49g heart, 59g thigh (both per day) and a bunch of other things. So I plugged in the vitamin K for 108 g "chicken meat" (heart + thigh, ignoring liver) and the NRC's requirement was met. Then I ran it again with only 59g of "chicken meat" in case the muscle of the heart is radically different from muscle meats commonly consumed in the West and likely to be analyzed by researchers. That brought me to 97% of the NRC's recommendations. Given that the other foods in this recipe are also using the USDA's measurements of only K1 and MK-4, it is likely that the K requirement is met.
A final note, Vermeer et. all (the 100mcg/100g in chicken study) found other meats to be much lower in K, with the exception of beef liver (112mcg/100g). So I will need to revisit this once I work on more diets. I figured I'd share my research with any other science nerds making their own cat food.
Two last fun facts on K, cooking does not diminish K content. Also, crickets (like you can buy at pet stores for reptiles) likely contain K. (That study was based on a supplemented diet, but K was not part of the supplementation. Also, I verified that most locations of Pet Supplies Plus sell the same species in that article.) The large crickets at Pet Supplies weigh about 0.2g on average, so 4 large crickets will meet a 9-lb cat's vitamin K needs.
