A study published in The Journal of Nutrition has revealed that insufficient vitamin K intake — specifically vitamin K2 as MK-4 — can have a profound negative impact on cognition within an ageing animal model.
This follows recent research revealing the vitamin's key role in promoting kidney and cardiovascular health, as well as managing long COVID symptoms and tackling neuroinflammation.
During the study, researchers from the dedicated research centre for ageing at Tufts University found that a lack of dietary exposure to vitamin K can enhance serum markers of inflammation.
It was also linked to a reduction in the generation of new neural cells within the hippocampus, a brain region crucial to key cognitive functions such as learning and memory.
These results highlight the key benefits of sufficient vitamin K intake, which — according to the US National Institutes of Health (NIH) — is 120 mcg for male adults, and 90 mcg for females.
Why vitamin K?
Vitamin K is commonly found in leafy green vegetables such as peas, spinach, kale and broccoli, and has been found to mediate the blood clotting cellular cascade.
The nutraceutical can also have positive effects on joint health through the modulation of osteocalcin, a key enzyme involved in the integration of calcium into the bone.
"There's also research that indicates vitamin K contributes to brain function," notes lead author of the study, Tong Zheng. "We already know that cognitive function declines during the ageing process, but studies seem to show that vitamin K has a protective effect,"
"Our research is trying to understand the underlying mechanism for that impact," he said.
The study
To assess the benefits of sufficient vitamin K intake through the diet, researchers conducted a six month dietary intervention on mice.
During the study period, the cognitive performance of mice fed either a diet low in vitamin K or a standard diet were monitored via a range of tests, such as the novel object recognition and spacial learning test.
Honing in on menaquinone-4, researchers noted that those fed a vitamin K deficient diet had significantly lower levels of the nutraceutical in their brain tissue.
The deficient mice also exhibited poor performance in the cognitive tests — experiencing a reduced ability to distinguish between familiar and new objects in a memory test and performing worse than their vitamin K sufficient counterparts in a spacial learning test.
When looking at the physiology of the studied mice, they found that vitamin K deficient models experienced a significant reduction in cell proliferation within the hippocampus; suggesting that insufficient vitamin K intake can impair neurogenesis.
"As neurogenesis is thought to play a critical role in learning and memory, its impairment could directly contribute to the cognitive decline observed in this study," stated Zheng.
Vitamin K deficient mice were also more prone to neuroinflammation, characterised by an increase in the activation of CNS immune cells such as microglia.
The chronic overactivation of microglia can lead to inflammation and age-related cognitive decline, though it appears that sufficient vitamin K intake is enough to offset this phenomenon.
So, what about supplements?
Although vitamin K is relatively easy to absorb through the diet, many people across the globe do not have access to foods rich in the vitamin.
This could be due to a lack of fruits and vegetables in their diet, as well as food insecurity the unavailability of fresh produce within their region.
Since there are a vast number of regions globally that don't have secure access to nutritious food, correcting a vitamin K deficiency may be a cost-effective and easy way to support cognition in ageing adults.
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