In a new study, overweight and obese older women who took more than three times the recommended daily dose of vitamin D showed an increase in memory and learning but also had slower reaction times. These slower reaction times may be part of the reason why falls seem to be more common among elderly who take higher doses of vitamin D.
The research team, led by Rutgers University, used computers to assess the impact of vitamin D on cognitive function in three groups of women between 50 and 70 years old.
One group took the recommended daily dose of 600 international units (IU), equivalent to 15 micrograms, of vitamin D each day for a year. Another group took 2,000 IU per day and the third took 4,000. All women received lifestyle counseling and were encouraged to lose a modest amount of weight.
The findings show that memory and learning improved in the group that took 2,000 IU per day, but not in the group that took the higher dosage. Meanwhile, the women’s reaction time showed a trend to be slower at 2,000 IU daily and was significantly slower at the higher dosage.
“The slower reaction time may have other negative outcomes such as potentially increasing the risk of falling and fractures,” said senior author Sue Shapses, Ph.D., R.D., a professor in the Department of Nutritional Sciences at Rutgers University-New Brunswick and director of the New Jersey Obesity Group.
“This is possible since other researchers have found that vitamin D supplementation at about 2,000 IU daily or more increased risk of falls, but they did not understand the cause. Our team’s findings indicating a slower reaction time may be one answer. Many people think that more vitamin D supplementation is better, but this study shows that is not always the case.”
Shapses says 4,000 IU a day might not be a problem for younger people, but for the elderly, this amount could compromise walking or catching one’s balance to avoid a fall because their reaction time is slower. However, this is still a presumption until future research can cover vitamin D levels, cognition and falls, she added.
Future research should also look at varying doses of vitamin D, from both supplements and dietary sources, in men and women of different ages and different races over a longer period of time, Shapses said. Larger studies are needed as well.
Cognitive impairment and dementia are significant public health problems, particularly in older adults. Evidence shows that vitamin D plays a role in cognition and the normal functioning of the central nervous system.
The findings are published in the Journals of Gerontology: Series A.
Source: Rutgers University