People with higher levels of vitamin D as they enter middle age may have a lower risk of developing dementia, new research suggests.
For the study, researchers measured vitamin D blood levels in about 800 adults without dementia who were on average 39 years old at the start of the study. Some 16 years later, when people were in their mid-50s, participants underwent PET scans of their brains to measure the buildup of tau and beta-amyloid proteins, substances associated with increased risk of dementia.
“Vitamin D may play an important role in preventing or delaying Alzheimer’s disease and dementia changes in the brain,” says study lead author Dr. Emer McGrath, associate professor of medicine at the University of Galway and consultant neurologist at Galway University Hospital in Ireland.
“Vitamin D may have beneficial effects by reducing inflammation in the brain, acting as an antioxidant, and reducing the collection of abnormal tau proteins in the brain,” Dr. McGrath says.
Elevated vitamin D levels were associated with decreased tau accumulation
The participants’ average vitamin D blood level was 38 nanograms per milliliter (ng/mL). Researchers defined readings below 30 ng/mL as low, and about one-third of participants fell into this group.
Compared to participants with low vitamin D levels, participants with high vitamin D levels had less tau accumulation in their 50s, including in areas of the brain where tau protein tends to accumulate first in people who develop dementia, the study found.
The association between high vitamin D levels and decreased tau accumulation remained strong even after the researchers accounted for several factors that may influence this association, including age, gender, the exact amount of time that elapsed between the vitamin D test and the brain scan, when the vitamin D test was taken, and health problems that may independently cause tau accumulation.
However, this study found no association between vitamin D levels in midlife and amyloid accumulation later in life. The researchers said this may be because tau accumulation begins earlier in the progression of dementia and at a younger age than amyloid accumulation.
This study has some limitations
The study was not a controlled experiment aimed at proving whether or how specific vitamin D levels can directly prevent or slow the progression of dementia.
One limitation of this study is that the majority of participants were white, so the results may not apply to people from other racial or ethnic groups.
Another drawback is that because the researchers looked at vitamin D levels at one point in time, it is impossible to determine how changes in vitamin D levels over many years affect future dementia risk.
Additionally, only 22 people were taking vitamin D supplements at the start of the study, so it’s impossible to determine what effect supplements have on future dementia risk.
Still, McGrath says the study adds to the evidence that vitamin D levels are a potential risk factor for dementia that people can control.
“Our findings suggest that lowering vitamin D levels in midlife may be a modifiable goal to reduce the risk of dementia later in life,” McGrath says. “But our results do not prove that [lack of] Vitamin D causes dementia. Further research is needed before regular vitamin D testing can be recommended to the community. ”
How to maintain good vitamin D levels
Most people don’t need supplements to maintain healthy vitamin D levels, says Helen Lavretzky, MD, geriatric psychiatrist, professor, and research director of the Integrative Medicine Collaborative at the University of California, Los Angeles.
“The best way to maintain healthy vitamin D3 levels is to combine safe sun exposure with dietary intake of fatty fish such as salmon, trout, mackerel, and herring, fortified foods such as cod liver oil, egg yolks, milk, orange juice, and cereals,” says Dr. Lavretzky, who was not involved in the study.
To absorb enough vitamin D, just 10 to 30 minutes of midday sunlight twice a week may be ideal, Labretsky added. But some people with darker skin or who don’t get much sun exposure due to climate or season may want to consider taking a lower daily vitamin D3 supplement, around 600 to 800 international units (IU), Lavretzky added.
Should I have my vitamin D levels checked?
“Regular vitamin D testing is not recommended for the general healthy population,” says Lavretsky.
Rather, it should be taken for people who are at higher risk of vitamin D deficiency, such as people with limited sun exposure, people with darker skin, and people who are at higher risk for health problems related to vitamin D deficiency. This group includes people who are obese, people over 65, and people with osteoporosis, Lavretsky said.
She also recommends that women get their vitamin D levels tested around the time they reach menopause. The rapid drop in estrogen that occurs during this transition period can reduce bone density, and vitamin D is important for maintaining stronger bones, she says.
However, when it comes to preventing dementia, Lavretsky says there is currently not enough evidence to support monitoring vitamin D levels.
“It’s still unclear how much increasing vitamin D actually reduces the risk of dementia,” Lavretzky says.
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