A Vitamin D Deficiency Could Affect Both Mood & Memory, Study Shows
It's no secret that vitamin D plays a vital role in everything from immunity to bone health, but. But many past studies have also linked a vitamin D deficiency (or insufficiency) to depression and cognitive decline (including dementia) over time.
Now, a new review brings fresh insight into how vitamin D may influence mood1 and how much of the vitamin you need to supplement with to improve your levels (and cognition).
About the study
For this study, researchers weren’t just interested in vitamin D’s impact on mood, but also its impact on brain-derived neurotrophic factor (BDNF).
BDNF is a protein that helps brain cells survive, grow, and communicate. When BDNF levels drop (which happens with age, high levels of inflammation, and damage from oxidative stress), your mood and cognition take a hit.
Previous research shows that people with depression and cognitive disorders (like dementia and Alzheimer’s disease) have lower levels of BDNF.
Vitamin D, meanwhile, may act as a trigger to the body to increase BDNF production, which would in turn, improve mood and cognition.
So, researchers reviewed studies published between 2009 and 2025 that explored the connection between vitamin D levels, brain-derived neurotrophic factor (BDNF), and outcomes related to mood and cognition.
Vitamin D supplements can improve mood
Researchers found that vitamin D supplementation consistently improved mood across the studies evaluated, especially in people who are deficient. For reference, vitamin D deficiency is when blood levels are at or below 20 ng/mL2, and 30 ng/mL2 is considered the upper end of insufficiency (or low vitamin D levels).
- Vitamin D supplements are especially important for mood: Taking higher doses of vitamin D (2,000 IU/day or more for about 12 weeks) improved mood in people who were low in vitamin D.
- Adequate vitamin D levels were linked to better cognition: This is most relevant over longer periods of supplementation.
- Vitamin D can raise BDNF: Higher doses of vitamin D supplements boost BDNF levels by about 7% in people with a deficiency.
- Hitting the target range matters: Getting vitamin D levels into the adequate range (above 30 ng/mL) is an effective way to improve mood and cognition.
- Pair vitamin D with other nutrients: Pairing vitamin D with nutrients like magnesium, zinc, omega-3s, probiotics, or regular exercise can double the brain and mood benefits.
How to supplement
Right now, around 29% of U.S. adults are considered straight-up vitamin D deficient3, and 41% are vitamin D insufficient3.
So most people need a supplement to first correct that inadequacy in the diet.
From there, the purpose of supplementation is to achieve vitamin D sufficiency (levels at 30 ng/mL or more) for life and then vitamin D optimization (levels at 50 mg/mL). And achieving optimal vitamin D levels requires a dose of about 5,000 IU a day.
If you’re looking for a vitamin D supplement to help raise your blood levels, here’s a list of our favorites.
The takeaway
Vitamin D has so many important roles in supporting our physical and mental health. And taking a high-quality vitamin D supplement daily is the most effective way and correcting a deficiency and protecting your cognition.
