Vitamin K and Cognitive Health

A recent study published in Alzheimer’s & Dementia: Translational Research & Clinical Interventions explored whether levels of vitamin K in the brain are linked to cognitive decline and brain changes associated with dementia. The study focused on a specific form of vitamin K, a derivative of vitamin K2 called menaquinone-4 (MK4), which is the primary type found in the human brain. While vitamin K is commonly known for its role in blood clotting, research over the past decade has suggested it may have much broader effects, including in brain health.

The researchers analyzed data from 325 older adults who participated in the Rush Memory and Aging Project, a long-term study based in Chicago. These participants had undergone regular cognitive testing and agreed to donate their brains for analysis after death. In this study, vitamin K levels were measured in four regions of the donated brains: the mid-temporal cortex, mid-frontal cortex, anterior watershed white matter, and the cerebellar cortex. The researchers then examined how these levels related to each person’s cognitive performance and the amount of Alzheimer’s disease and other dementia-related pathology found in the brain tissue.

The key finding was that individuals with higher levels of MK4 in their brains performed better on cognitive tests before their deaths. Specifically, participants with the highest brain MK4 levels had a 17% to 20% lower chance of having been diagnosed with dementia or mild cognitive impairment during their lifetimes. They also experienced slower rates of cognitive decline, suggesting that vitamin K may play a protective role in how the brain ages. In addition to better cognitive function, higher brain MK4 levels were also linked to fewer physical signs of Alzheimer’s disease in the brain. These included lower total Alzheimer’s pathology scores, fewer neurofibrillary tangles (which are twisted strands of protein inside neurons), and lower Braak staging, which is a scale used to measure the spread of Alzheimer’s-related changes.

Moreover, participants with more MK4 in their brains had fewer Lewy bodies, which are abnormal protein deposits that are associated with another form of dementia called Lewy body dementia. The consistency of these findings across multiple regions of the brain adds weight to the idea that vitamin K, especially MK4, could play a role in reducing brain damage linked to cognitive decline.

The researchers also looked at blood levels of a different form of vitamin K—phylloquinone, or vitamin K1—which is found in green leafy vegetables like spinach and kale. They found that higher levels of K1 in the blood were associated with better cognitive performance, but there was no significant correlation between blood K1 levels and the amount of MK4 in the brain. Nor were blood K1 levels significantly associated with the amount of Alzheimer’s disease pathology found at autopsy. This suggests that although K1 may support cognition in some way, it may not directly reflect what is going on inside the brain in terms of vitamin K concentrations.

Taken together, the findings suggest that vitamin K, and specifically MK4, may influence brain aging in ways that are not yet fully understood. There are several possible explanations for how MK4 might exert these effects. Vitamin K has antioxidant properties, meaning it can help neutralize harmful molecules called reactive oxygen species that damage cells, including neurons. Vitamin K is also involved in regulating calcium in the brain, which plays a critical role in communication between nerve cells. Additionally, MK4 may influence the expression of genes involved in brain development, maintenance, and repair.

From a public health standpoint, this study supports the idea that nutrition may have a major role in brain health and aging. Ensuring that people get enough vitamin K in their diets—especially older adults—could be a simple, low-cost strategy to help preserve cognitive function. Vitamin K1 is abundant in foods like kale, spinach, broccoli, and other leafy greens, while MK4 is found in animal products such as egg yolks, liver, butter, and some types of cheese, as well as in certain fermented foods. It’s worth noting that the body can convert K1 to K2, though this conversion is not always efficient and may vary between individuals. Supplementation with K2, particularly MK4, could be explored as a potential intervention, although this would require further clinical trials to assess efficacy and safety.

However, the authors caution that this was an observational study, so it cannot prove that higher brain vitamin K levels directly cause better cognitive function or lower levels of brain pathology. It is also possible that people who had better overall health throughout life—for example, due to a better diet or lifestyle—had both higher MK4 levels and slower cognitive decline. Additionally, most of the participants were older white adults, which limits how well the findings can be applied to other populations. Another consideration is the challenge of accurately measuring nutrient levels in stored brain tissue, although the researchers took care to control for how long the brains were stored before analysis.

The findings nonetheless raise intriguing questions about the role of nutrition, and particularly fat-soluble vitamins, in protecting the aging brain. Future studies, particularly randomized controlled trials on vitamin K supplements, are needed to determine if increasing dietary intake of K1 or K2 can prevent or delay cognitive decline and dementia. For now, the research adds to a growing body of evidence suggesting that what we eat may significantly impact not only our bodies but also our brains. Simple steps like eating more leafy greens, enjoying fermented foods, or ensuring sufficient intake of vitamins like K may have long-term effects on how well we think, remember, and function as we grow older.

In summary, this study presents compelling evidence that higher levels of vitamin K—especially the MK4 form found in the brain—are associated with better cognitive function and fewer markers of dementia-related damage in older adults. While it doesn’t prove that vitamin K prevents dementia, the findings offer a promising new direction for research and underscore the importance of nutritional strategies for cognitive health.