Scientists from Rutgers University found that vitamin D could improve memory in older women but too much supplementation could slow down their reaction speed in cognitive tasks.
Vitamin D is a nutrient the body needs to build and maintain healthy bones. That’s because the body can only absorb calcium, the primary component of bone when vitamin D is present.
Vitamin D also regulates many other cellular functions in the body.
Previous research has found that vitamin D is neuroprotective, regulates the immune system, and helps with calcium balance.
It is also involved with regulating many genes important for brain function. Although vitamin D is thought of as a vitamin, it acts as a neurosteroid and plays important roles in the brain.
Recent studies also found that vitamin D may affect cognitive performance, but previous studies are either short-term or observational.
In the current study, the team examined the effects of vitamin D supplementation on cognitive functions in older women.
They tested overweight or obese women with serum 25-hydroxyvitamin D (25OHD) levels less than 30 ng/mL.
These women received vitamin D3 supplementation (600, 2,000, or 4,000 IU/d) for 1 year.
Previous studies have repeatedly shown that vitamin D3 is superior at raising levels of vitamin D in the body.
The researchers measured the blood 25-hydroxyvitamin D, bone density, amyloid beta, parathyroid hormone, and estrogen before and after supplementation.
Amyloid beta is the main component of the amyloid plaques found in the brains of people with Alzheimer’s disease.
Parathyroid is a gland next to the thyroid which secretes a hormone ( parathyroid hormone ) that regulates calcium levels in the body.
The participants also took cognitive tests after treatment.
The researchers found that women taking 2,000 IU/d compared to other doses performed better in learning and memory tests, but the 4,000 IU/d groups had a slower reaction time compared to the 600 IU/d groups.
They also found that bone density predicted tasks associated with reaction time and executive function, whereas body mass index and parathyroid hormone negatively predicted reaction time and executive function.
Executive function is a set of mental skills that include working memory, flexible thinking, and self-control. People use these skills every day to learn, work, and manage daily life.
These findings suggest that vitamin D has differential effects on cognitive functions and that a higher dose may negatively affect reaction time.
The team suggests that 4,000 IU of vitamin D a day may be dangerous to older people because it can disrupt walking or one’s balance.
One limitation of the study is whether reaction time is related to risks of falls and injuries in people with a high risk is still unknown.
Another limitation is how different doses of vitamin D supplementation may affect women and men separately is still unclear. More studies are needed to solve the issues.
The research was published in the Journal of Gerontology and was conducted by Sue Shapses et al.
If you care about nutrition, please read studies about how the Mediterranean diet could protect your brain health, and Vitamin B supplements could help reduce dementia risk.
For more information about nutrition, please see recent studies about antioxidants that could help reduce dementia risk, and Vitamin D deficiency linked to higher dementia risk.
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