Healthy men and women over the age of 70 with the highest average blood levels of phylloquinone (vitamin K1) had higher verbal episodic memory performance, compared to people with lower blood levels.
“Episodic memory refers to the memory of events within their spatio-temporal context,” explained the researchers in Neurobiology of Aging. “For example, remembering where one's keys were last left relies on episodic memory. It is thus important to everyday life.”
On the other hand, scientists from the University of Montreal in Canada reported that vitamin K status was not associated with executive functions and speed of processing.
“To our knowledge, this is the first published study to examine the association between vitamin K and cognitive outcomes in healthy older adults,” wrote the researchers. “Notably, we found a positive association between serum phylloquinone and performances in verbal episodic memory, with a pattern suggesting a specific role in memory consolidation.
“In line with rodent models, our results are biologically plausible and add evidence for an expanding role of vitamin K from coagulation to cognition.
“The present report emphasizes the need to consider vitamin K as a nutritional factor in cognitive health in the aging population.”
There are two main forms of vitamin K: phylloquinone, also known as phytonadione, (vitamin K1) which is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90% of the vitamin K in a typical Western diet; and menaquinones (vitamins K2), which make up about 10% of Western vitamin K consumption and can be synthesized in the gut by microflora.
Menaquinones (MK-n: with the n determined by the number of prenyl side chains) can also be found in the diet; MK-4 can be found in animal meat, MK-7, MK-8, and MK-9 are found in fermented food products like cheese, and natto is a rich source of MK-7.
The new study, led by Guylaine Ferland, PhD, only measured serum phylloquinone concentrations and no association could be made between vitamin K2 levels and brain health.
“Phylloquinone is the main K vitamer in diet and available data indicate that other K vitamers found in the North American diet as well as menaquinones synthesized by gut bacteria would not be significant contributors to vitamin K status,” they explained.
Using data from 320 participants in the Québec Longitudinal Study on Nutrition and Successful Aging (NuAge), Dr Ferland and her co-workers found that higher phylloquinone levels were associated with better verbal episodic memory performance, including the 20-minute delayed free recall trials.
No links were found between phylloquinone levels and other measures of cognitive function.
Commenting on the potential mechanism, the researchers stated: “The vitamin K-dependent proteins Gas6 (growth arrest-specific gene 6) and protein S are expressed in the central nervous system. Protein S is notably known to possess neuroprotective effects during hypoxic/ischemic injury, whereas Gas6 is now recognized as an important regulator of cell survival, cell growth, and myelination processes.
“Furthermore, vitamin K participates in the metabolism of sphingolipids, a major constituent of the myelin sheath and neuronal membranes, also involved in important molecular events such as cell signaling.”
Source: Neurobiology of Aging
Volume 34, Issue 12, Pages 2777–2783, doi: 10.1016/j.neurobiolaging.2013.05.031
“Vitamin K status and cognitive function in healthy older adults”
Authors: Presse N, Belleville S, Gaudreau P, Greenwood CE, Kergoat MJ, Morais JA, Payette H, Shatenstein B, Ferland G.