Vitamin D seems to be in the news constantly – in fact, only last week, we mentioned that low vitamin D levels may be associated with Multiple Sclerosis.  New research suggests people with very low levels of vitamin D in their blood, known as vitamin D deficiency, are more likely to develop Alzheimer’s disease and other forms of dementia.

This recent study, published in JAMA Neurology, has confirmed that significantly low vitamin D levels reflect a decline in cognitive ability.  The findings indicate that low vitamin D levels can also be responsible for brain structure abnormalities, cognitive decline and incident dementia.

In the United States, deficiency and insufficiency of vitamin D are prevalent, especially in older people. “Insufficiency” is classified as 25-OHD blood levels between 12-20 ng/mL, and “deficiency” is less than 12 ng/mL.

The National Health and Nutrition Examination Survey (NHANES) previously found that 42% of the general adult population were either deficient or insufficient in vitamin D, with the percentage rising to over 50% after age 65.  The prevalence was even higher among Hispanic (69%) and African-American (82%) individuals.

» 3 primary causes for low vitamin D levels

  • Not eating the recommended levels of vitamin D in food
  • Limited exposure to sunlight
  • Darker skin color

» Vitamin D research study

In recent research, Joshua W. Miller, PhD, of Rutgers University in New Brunswick, NJ, and co-authors from the University of California-Davis, examined vitamin D levels and change in cognitive function among 382 people, enrolled from an outpatient clinic in California between February 2000 and August 2010.

» Results

Results showed that participants who had been deficient in vitamin D experienced a greater decline in cognitive ability and episodic memory.  Overall, the results supported previous findings that older adults lack vitamin D, and also confirmed that Hispanic and African-American individuals are more likely to do so.  They also illustrated an apparent link between lack of vitamin D and cognitive impairment.

“Vitamin D insufficiency was associated with significantly faster declines in both episodic memory and executive function performance, which may correspond to elevated risk for incident AD [Alzheimer’s disease] dementia.”

However, while lack of vitamin D appears to be linked to lower cognitive function, the benefit of giving supplements is not yet established.  The authors point out that “it remains to be determined whether vitamin D supplementation slows cognitive decline.”

» Reference