- Researchers have noted an association between high vitamin D levels and low levels of tau protein on brain scans after several years.
- Tau protein is a biomarker for Alzheimer’s disease, the leading cause of dementia.
- There was no association between vitamin D and levels of amyloid-beta, another Alzheimer’s biomarker.
The authors of a new study have reported that having higher levels of vitamin D was associated with lower levels of tau protein — a biomarker for Alzheimer’s disease — several years later.
“These results suggest that higher vitamin D levels in midlife may offer protection against developing these tau deposits in the brain,” said study author Martin David Mulligan, MB BCh BAO, of the University of Galway in Ireland in a press release.
“Low vitamin D levels could potentially be a risk factor that could be modified and treated to reduce the risk of dementia.”
Vitamin D is a fat-soluble vitamin that the body produces when sunlight touches the skin. Most people can obtain what they need through sun exposure, but during winter months, when there is less sunlight, people can get it from supplements and some foods.
This vitamin is important for keeping bones, muscles, and teeth healthy by regulating the amount of calcium and phosphorus in the body. It can also play a role in reducing inflammation, supporting the immune system, and managing glucose levels.
For the study, published in Neurology Open Access, an official journal of the American Academy of Neurology, the researchers looked at 793 participants who did not have dementia. The participants had an average age of 39 at the start of the study.
At the beginning of the study, researchers measured the levels of vitamin D that participants had using blood tests.
The researchers defined high levels of vitamin D as being greater than 30 nanograms per milliliter (ng/mL). They defined anything less than this amount as being a low level of vitamin D.
At this stage, around 34% of the participants had low levels of vitamin D, with 5% taking a vitamin D supplement.
After an average of 16 years, brain scans then measured the amounts of tau and amyloid beta proteins present in the brains of the participants.
Buildups of these two proteins in the brain are associated with the development of Alzheimer’s disease, the most common cause of dementia.
After adjusting for factors that could affect the levels of tau, such as age, sex, and depression, the researchers found that having higher levels of vitamin D was associated with lower levels of tau protein.
There was no association between vitamin D and amyloid-beta levels, however. Medical News Today asked Mulligan why he thought this might have been the case.
“Accumulation of tau in some areas of the brain may occur earlier than the build up of amyloid,” he said.
“The participants in our study were relatively young when blood samples were obtained, and so an association between vitamin D and tau, compared to amyloid protein, may be more likely to be detected in a younger population.”
“These results are promising, as they suggest an association between higher vitamin D levels in early middle-age and lower tau burden on average 16 years later,” said Mulligan in the press release.
“Mid-life is a time where risk factor modification can have a greater impact.”
This study has a number of limitations, however, which means people should be careful with how much importance they place on these findings for now.
A key limitation is that the researchers only had one measurement of vitamin D from the beginning of the study. Over the years that passed before the brain scans, the participants’ vitamin D levels may have changed significantly.
The way that the researchers measured vitamin D levels was also quite limited, defining a participant’s levels as either high or low with no middle ground.
Labelling levels above 30 ng/mL as high meant that someone with a level of 30 ng/mL would fall into the low level group. Experts define levels of 20 ng/mL and above as being adequate for overall health.
The researchers opted for this cutoff point rather than 20 ng/mL as this measurement had previously featured in previous studies with older groups of participants. In contrast, there was a relatively small number of people with levels lower than 20 ng/mL in this study’s sample.
Higher vitamin D levels may not have been the reason for the relatively lower tau levels.
MNT spoke with Steve Allder, MD, a consultant neurologist at Re:Cognition Health in London in the United Kingdom, who was not involved with the study. He explained what other factors may have been at work.
“Higher vitamin D levels may simply be a marker of overall better health rather than the driver of reduced tau pathology. For example, individuals with higher vitamin D are often more physically active, spend more time outdoors, and may have healthier diets, all of which are independently linked to better brain health.”
– Steve Allder, MD
“Socioeconomic status, access to healthcare, and lower rates of chronic disease could also play a role,” he added.
“Of course, these results need to be further tested with additional studies,” said Mulligan in the press release.
Getting sufficient amounts of vitamin D is important for overall health, but there are clearer steps people can take to reduce their risk of Alzheimer’s disease and dementia.
While people cannot control some risk factors for Alzheimer’s, such as age and genetics, people can adjust other factors associated with the disease.
MNT also asked Dung Trinh, MD, internist for MemorialCare Medical Group and chief medical officer of Healthy Brain Clinic in Irvine, CA, about Alzheimer’s risk reduction.
“The strongest evidence still supports a multifactorial prevention approach, not a single nutrient or intervention,” Trinh said.
“Vitamin D may play a role in overall health, but it should be viewed as one small piece of a much larger prevention strategy — not a standalone solution.”
