Vitamin K shot doesn’t stop stem cells from circulating or change blood thickness

Medical practitioners recommend the vitamin K shot for newborns to prevent a potentially life-threatening condition known as vitamin K deficiency bleeding. But misinformation is contributing to a growing refusal of the shot by parents.

Science Feedback covered some of the most common false claims about the vitamin K shot in previous reviews, specifically about the safety of the ingredients in the shot. In this article, we address another piece of misinformation about the vitamin K shot, namely the belief that vitamin K deficiency in newborns is actually beneficial and that the vitamin K shot allegedly prevents stem cells from repairing post-birth injuries.

These claims have been spread by various health and wellness influencers on social media. One example of such a post came from chiropractor Daniel Pompa, whose TikTok video was viewed more than 174,000 times. Another example of such a post was published by the X account @ValerieAnne1970, viewed more than 116,000 times.

These posts promote a scientifically unfounded claim and a misunderstanding of what vitamin K does in the body. We explain.

Vitamin K shot doesn’t make the blood “thicker” or more viscous

The idea that vitamin K makes the blood thicker and thus blocks stem cells from circulating in the body may potentially be based on the fact that it plays a role in blood clotting. However, vitamin K isn’t enough to trigger blood clotting on its own.

Under normal circumstances, blood clotting occurs in response to injury and clotting is facilitated by many proteins in the clotting cascade (also called the coagulation cascade), shown in the diagram below. These proteins are also called clotting factors (the capital F in front of each protein’s name stands for “factor”. Vitamin K isn’t involved in the cascade itself, but the body needs it to make the proteins involved in the cascade. Vitamin K deficiency means that there aren’t enough of these proteins, which increases the risk of a spontaneous bleed.

Mitigating vitamin K deficiency means that the body has enough vitamin K to make the proteins that are part of the coagulation cascade. However, this is not sufficient on its own to trigger clotting. This is because our body has anti-clotting mechanisms in place to prevent clotting in the absence of a bleed or injury.

If these anti-clotting mechanisms didn’t exist, otherwise healthy people would spontaneously develop blood clots in their body, even without a bleed or injury, leading to complications like stroke and heart attack.

These anti-clotting mechanisms also ensure that blood clotting is confined only to the site of injury or bleeding, and that it doesn’t take place elsewhere in the body. Otherwise, a cut on the hand could lead to a clot in the leg, for instance.

In summary, the mechanisms governing blood clotting are finely tuned to ensure that clotting only takes place when and where it’s needed. The vitamin K shot given at birth is incapable of overriding these mechanisms.

Vitamin K deficiency: no known benefit, established risk

Babies are born deficient in vitamin K because the vitamin doesn’t pass through the placenta easily. Another reason is because the intestinal microbiome contributes to our vitamin K stores, but it is immature in newborns and therefore unable to contribute vitamin K at this early stage of life. While breast milk and formula contain some vitamin K, this amount is small and ineffective at mitigating deficiency after birth.

In their social media posts, Pompa, Smith and others claimed that the low level of vitamin K in newborns is meant to serve a greater purpose, like facilitating healing and development. If this were the case however, we would expect to see infants who received the shot to have poorer health and developmental outcomes compared to infants who didn’t receive it. But there is no scientific evidence to support this idea and neither Pompa nor Smith provided evidence to show that this is true.

On the other hand, there is clear evidence to show that skipping out on the vitamin K shot comes with significant risks. These include bleeding in the brain, which can result in permanent neurological damage, and death^[1].

The American Academy of Pediatrics recommended as early as 1961 that all newborns receive a single intramuscular injection of vitamin K shortly after birth^[2]. The European Standards of Care for Newborn Health also considers this to be best practice, stating that “the best protection [against VKDB] is to administer newborns 1 mg of vitamin K intramuscular at birth”.

It is true that not all infants who don’t receive the vitamin K shot will develop bleeding, but there is no way to know beforehand which infants will develop a bleed and which ones won’t. Moreover, the established side effects of the vitamin K, when compared to a bleed, are comparatively minor: these include pain and swelling at the injection site. Severe allergic reactions can occur, but these are very rare and they aren’t caused by toxic ingredients but a misdirected immune response against a harmless substance.

In summary, when the risks and benefits of the shot are weighed against each other, the scientific evidence favors the administration of the vitamin K shot for all infants at birth.

References:

1. Shearer MJ. (2008) Vitamin K deficiency bleeding (VKDB) in early infancy. Blood Reviews.
2. Hand et al. (2022) Vitamin K and the Newborn Infant. Pediatrics..