- Experts are interested in how certain vitamin deficiencies may affect the brain.
- One study suggests that mice with low vitamin K levels had worse learning and memory function than mice without low vitamin K levels.
- The results also indicate that the observed cognitive declines might be related to how vitamin K affects the formation of neurons in the hippocampus of the brain and neuroinflammation.
Previous research has suggested that vitamin K may affect cognitive function. A recent study published in The Journal of Nutrition sought to explore the cognitive effects of vitamin K — though in mice.
The results found that mice fed a low vitamin K diet had lower vitamin K levels in the brain and had poorer cognitive function than mice that did not receive the low vitamin K diet.
The findings point to the importance of vitamin K and the need for more extensive research in this area.
Researchers of the current study note that low vitamin K could impact “age-related cognitive decline.” For this study, researchers wanted to use mice to explore the effects of low vitamin K and look at some of the possible underlying biological mechanisms.
This study used middle-aged male and female mice who either received a low vitamin K diet or a regular diet for six months.
Researchers used behavioral testing to measure aspects of cognitive function, like spatial learning and recognition memory. David C. Hess, MD, Dean at the Medical College of Georgia and a neurologist and stroke specialist, who was not involved in the study, explained that “One of the tests they use is a novel object recognition. So a smart mouse is going to explore a new object it’s never seen before… this is a very standardized test that we do in the lab to measure cognition.”
Another test was the Morris water maze, which involved finding a hidden underwater platform based on previous tests.
After behavioral testing, researchers were able to examine the brain tissue of mice for further analysis, as well as vitamin K in the liver and kidneys.
Low vitamin K vs. regular diet
Overall, mice on the low vitamin K diet saw worse outcomes than mice who received a regular diet. For one thing, researchers found that male mice who had the low vitamin K diet had a decreased survival rate. They also had a lower weight gain than female control mice. Female mice on the low vitamin K diet did not experience these effects.
The researchers also found that mice on the low vitamin K diet had lower levels of Menaquinone-4 (MK4) in the brain. MK4 is the major form of vitamin K when it is present in the brain. There were also lower levels of vitamin K in the liver and kidneys of the mice on the low vitamin K diet.
In the novel object recognition test, mice on the low vitamin K diet did not explore the novel object as much as the control mice. This implies these mice had problems with recognition memory.
Mice on the low vitamin K diet also took longer on the first three days of the Morris water maze learning how to locate the hidden platform. Over the four days, they also took longer than controls, but this level did not reach a level of statistical significance.
Researchers also noted differences in the hippocampus area of the mice’s brains if they were on the low vitamin K diet. The mice with the low vitamin K diet had decreased neurogenesis in this brain area. Neurogenesis has to do with the body creating neurons that are mature and able to appropriately function. These findings suggest that vitamin K may affect neurogenesis.
Hess explained the following to Medical News Today:
“In mice and in all mammals, we don’t make new neurons, usually throughout the brain. We make them in specific areas. So one area where they’re made, and this has actually also been shown in humans, is the dentate gyrus of the hippocampus. So the hippocampus is the part of the brain that’s best associated with recent memory, which is affected very early in Alzheimer’s disease.”
The study authors speculate that vitamin K’s impact on hippocampal neurogenesis may then affect cognitive functions like learning and memory that are related to the work of the hippocampus.
The researchers also found that mice on the low vitamin K diet had changes in specific cells called microglial cells in the hippocampus, which suggested the activation of these cells. These observations of the microglial cells indicated increased neuroinflammation.
These results suggest that low vitamin K may induce an increase in neuroinflammation.
The authors speculate that vitamin K might protect hippocampal neurogenesis in part through its anti-inflammatory effects. Vitamin K’s effects on cognition could also be somewhat related to how it affects inflammation and protects against oxidative stress.
This research offers critical insight into the potential impact of vitamin K on learning and memory. However, it also has limitations.
For one thing, mouse studies provide limited information on how low vitamin K affects brain function in people. The researchers also chose to focus on a specific form of vitamin K that is present in human diets.
They also only had so many mice left for behavioral testing because of the higher death of male mice in the low vitamin K diet group. The authors acknowledge that the final endpoints of the study also did not have data from the male mice who died before the study was over.
Other factors could have affected the observed results, too. For example, the authors note that vitamin K could be involved in metabolizing a cell membrane component called sphingolipids. They note that sphingolipids “contribute to proliferation, differentiation, and neuroinflammation.” They explain that more research is required to see if the changes to sphingolipids from low vitamin K are involved in neuroinflammation and hippocampal neurogenesis.
The researchers were also unable to measure proteins dependent on vitamin K in the brain and levels of an enzyme called γ-glutamyl carboxylase because of the limited amount of brain tissue and the experiments they ran. It’s possible these proteins were responsible for the observed effects of vitamin K, so more research is likely required.
It’s also unclear how the severity of impairment from vitamin K deficiency relates to the time frame of deficiency and mouse age. More research is also needed to understand the observed differences between male and female mice. These aspects can all be looked at in future research.
Ryan Hakimi, DO, MS, a neurointensivist and osteopathic physician, who was not involved in the study, noted the following regarding the potential clinical implications to Medical News Today:
“The study reinforces the importance of healthy dietary habits for improved cognitive function. Perhaps primary care physicians and those who treat cognitive dysfunction can reinforce with their patients the importance of a healthy diet rich in Vitamin K-containing foods, especially for those who have a family history of dementia.”
Food sources for vitamin K“High Vitamin K levels are noted in dark leafy vegetables, certain fruits like kiwi and blueberries, eggs, soybeans, and vegetable oil amongst other food items.”
— Ryan Hakimi, DO, MS