Vitamin D may play a role in brain health, especially for older adults who already have sleep problems and early changes in memory or thinking.
A new study from Emory University found that people in this high-risk group who took higher amounts of vitamin D supplements performed better on a standard test of cognitive function.
The research was published in the journal Sleep Medicine. It included 54 adults who had both sleep disturbances and mild cognitive impairment, often shortened to MCI.
Mild cognitive impairment means a person has noticeable problems with memory or thinking that are greater than expected for normal aging. However, these problems are not severe enough to interfere greatly with everyday life, and not everyone with MCI will go on to develop dementia.
Sleep problems are also common in older adults and may become more frequent in people with cognitive decline. Poor sleep can affect memory, attention, mood, and the brain’s ability to recover from daily stress.
The researchers wanted to know whether vitamin D supplement use was related to thinking ability in people who had both MCI and sleep difficulties. Vitamin D is best known for helping the body absorb calcium and maintain healthy bones, but it also supports muscles, nerves, and the immune system.
Vitamin D may also be connected with sleep and brain function. Earlier studies have linked low vitamin D levels with insomnia, frequent nighttime waking, and some forms of cognitive decline, although these studies have not proved that low vitamin D directly causes these problems.
In the Emory study, participants reported how much vitamin D they took each day. The researchers then compared supplement intake with scores on the Montreal Cognitive Assessment, or MoCA.
The MoCA is a widely used screening test that checks several areas of thinking, including memory, attention, language, planning, and problem-solving. Lower scores can suggest a higher chance of cognitive impairment, although the test by itself cannot diagnose dementia.
Participants who reported taking at least 5,000 international units, or IU, of vitamin D per day scored more than 13% higher on the MoCA than people who did not take vitamin D supplements. The difference remained even after the researchers adjusted for several other factors.
Lower doses did not show the same clear connection with better cognitive scores. This finding suggests that the amount of vitamin D may matter, although the study was too small to establish an ideal dose.
The researchers also compared vitamin D2 and vitamin D3. Vitamin D2 is often made from plant or fungal sources, while vitamin D3 is the form the body naturally produces in the skin after sunlight exposure and is also found in some animal foods.
Cognitive scores were similar between people taking D2 and those taking D3. This suggests that, in this small group, the form of vitamin D may have been less important than the overall amount.
Senior author Victoria Pak of Emory University’s Nell Hodgson Woodruff School of Nursing said people with both sleep problems and MCI may be at an important stage for early intervention. At this point, cognitive changes have started, but there may still be opportunities to support brain health.
The study is especially relevant because Alzheimer’s disease and other dementias are becoming more common as populations age. More than 7 million Americans are currently living with Alzheimer’s dementia, and that number is expected to rise sharply in coming decades.
Still, the findings should be interpreted cautiously. The study involved only 54 participants, which is a very small sample compared with the number usually needed to make strong treatment recommendations.
The study also looked at reported supplement use rather than assigning people randomly to take different vitamin D doses. That means it cannot prove that vitamin D caused the better cognitive scores.
People who take high-dose supplements may differ from non-users in other ways, such as diet, income, health awareness, medical care, or physical activity. Any of these factors could influence cognitive performance.
Another important point is safety. A daily intake of 5,000 IU is higher than the usual recommended daily amount for most adults, and too much vitamin D over time can cause high calcium levels and other health problems.
For that reason, people should not start high-dose vitamin D solely because of this study without discussing it with a doctor. Blood testing may be useful for people at risk of deficiency, and the safest dose can depend on health conditions, medications, diet, and existing vitamin D levels.
Overall, the study offers an interesting early clue that vitamin D intake may be linked to better cognitive performance in older adults with MCI and sleep problems. However, larger randomized trials are needed before researchers can know whether vitamin D supplements can truly protect thinking ability or reduce dementia risk.
Source: Emory University.
