The Sunshine Vitamin and Your Brain: What the Latest Research Reveals
Everwood Reserve | Resident Wellness
Vitamin D Deficiency, Aging, and Cognitive Health: What Families Should Know
Vitamin D deficiency is rampant in older adults, and emerging science links it to accelerated cognitive decline. Here is what families and care teams need to know.
At Everwood Reserve, our approach to memory care and assisted living begins with a foundational belief: prevention starts long before a diagnosis. One of the most underappreciated tools in that effort, sitting quietly in your bloodwork, is vitamin D.
Often dismissed as merely a “bone vitamin,” vitamin D is increasingly recognized as a powerful neuroactive hormone with far-reaching effects on brain health, immune function, mood regulation, and longevity. And the population most at risk for deficiency? Older adults — the very people we serve every day.
Part One: Why Older Adults Are Running Low
Vitamin D deficiency is not a fringe concern. Research consistently shows it affects anywhere from 40 to 70 percent of older adults globally, with the highest rates found among nursing home residents and those with multiple chronic conditions. The reasons are multifactorial.
As we age, the skin’s capacity to synthesize vitamin D from sunlight declines significantly. Reduced time outdoors, decreased dietary intake, impaired kidney and liver conversion, and common medications all compound the problem.
And in sunbelt states like Texas, where many assume sun exposure is ample, indoor living habits and sunscreen use often tell a different story.
Vitamin D deficiency has been linked to:
- Cardiovascular disease
- Compromised immunity
- Depression
- Increased fall risk
- Bone fragility
- Neurodegenerative disorders
These are not independent concerns. In older adults, they often travel together.
“More than half of adults over 50 exhibit vitamin D concentrations below optimal thresholds, and nearly half of those affected are not taking any supplement at all.”
— English Longitudinal Study of Ageing
Part Two: Vitamin D and the Brain — Deeper Than We Thought
Decades of research assumed vitamin D’s role in the brain was indirect, supporting vascular health, reducing inflammation, and perhaps lifting mood. But the science has grown far more specific — and far more compelling.
Vitamin D receptors (VDRs) are distributed widely throughout the brain, including the:
- Hippocampus
- Cortex
- Cerebellum
- Substantia nigra
The brain does not just respond to vitamin D; it actively converts and uses it locally.
Astrocytes, the brain’s support cells, express VDRs that, when activated, initiate protective gene transcription pathways.
What Activated Vitamin D Does in the Brain
Neuroinflammation Control
Vitamin D suppresses pro-inflammatory cytokines and microglial activation — a central driver of age-related cognitive decline and Alzheimer’s pathology.
Amyloid-Beta Clearance
Active vitamin D promotes clearance of amyloid-beta plaques and reduces their formation.
Tau Hyperphosphorylation
Vitamin D reduces age-related tau hyperphosphorylation, a process linked to neurofibrillary tangles and neuronal instability.
Neurogenesis and Synapses
Vitamin D supports neurogenesis and promotes proteins required for new synapse formation, especially within the hippocampus — the seat of memory.
Beyond structural support, vitamin D also regulates key neurotransmitters including:
- Acetylcholine
- Dopamine
- Serotonin
- GABA
It also supports nerve growth factor (NGF) production, helping protect hippocampal and cortical neurons.
This is a hormone the brain is clearly designed to use — and when it is absent, the consequences may accumulate quietly over years.
Part Three: What the Research Shows About Dementia Risk
A major 2025 meta-analysis published in Frontiers in Neurology, synthesizing 22 studies and more than 53,000 participants, found that individuals with the lowest vitamin D levels carried a 49 percent higher relative risk of developing dementia compared to those with the highest levels.
The relationship demonstrated a dose-response pattern:
As vitamin D levels declined, dementia risk climbed.
Separately, a landmark study published in Neurology in April 2026 followed 793 adults from midlife and measured vitamin D levels at baseline.
Years later, researchers found that participants with higher midlife vitamin D levels had measurably lower deposits of tau protein in the brain.
Tau accumulation is considered one of the earliest detectable markers of Alzheimer’s pathology.
“Higher vitamin D levels in midlife may offer protection against developing tau deposits in the brain, with low vitamin D potentially setting the stage for future cognitive risk.”
— Neurology, April 2026
It is important to recognize the nuance in the evidence.
Some supplementation trials in already-sufficient populations have not demonstrated dramatic reductions in dementia incidence. A 2025 Finnish trial found no significant benefit from supplementation in adults who were not deficient at baseline.
The strongest protective signal appears to come from identifying and correcting true deficiency — especially in high-risk populations.
Part Four: General Health Benefits Beyond the Brain
Even outside cognitive health, the systemic benefits of adequate vitamin D in older adults are well established.
Bone and Muscle Health
Vitamin D is essential for calcium absorption and bone mineralization. Deficiency accelerates bone loss and increases fracture risk.
Fall-related fractures remain one of the leading causes of morbidity and loss of independence in seniors.
Immune Function
Vitamin D acts as an immunomodulatory hormone, regulating both innate and adaptive immune responses.
Deficiency is associated with increased susceptibility to respiratory infections and more severe illness outcomes.
Mood and Depression
Low vitamin D is consistently associated with depressive symptoms in older adults.
Given the overlap between depression and cognitive decline, this represents a meaningful and modifiable target.
Cardiovascular and Metabolic Health
Emerging evidence links adequate vitamin D levels to:
- Better blood pressure regulation
- Reduced diabetes risk
- Lower rates of certain cancers
These conditions commonly overlap in aging populations.
Part Five: Why This Is Personal to Me
I take 5,000 IU of vitamin D3 daily with a meal since it is best absorbed as a fat-soluble supplement.
My reasons are not purely clinical.
I train with weights four to five days per week, and bone density, muscle function, and long-term skeletal integrity are things I think about actively — not just in the context of patient care, but in my own life.
Vitamin D is a foundational part of that.
I also carry what I have learned into my family.
My mother is in her 60s, and as a Caucasian female, she carries a disproportionately elevated risk for osteoporosis.
I placed her on a protocol that includes:
- 5,000 IU of vitamin D3
- Vitamin K2
- Structured resistance training
K2 works synergistically with vitamin D to direct calcium toward the bones rather than allowing it to deposit in soft tissue.
This kind of proactive, whole-person approach reflects what we believe in at Everwood Reserve.
My interest in vitamin D sharpened significantly during COVID-19, when outcome data linked deficiency with substantially worse illness severity.
The consistency of that data reinforced my belief that vitamin D deserves far more attention than it currently receives.
This is the lens through which we think about resident wellness at Everwood Reserve:
Not reactive.
Not minimal.
But curious, evidence-informed, and individualized care at its core.
The Everwood Reserve Commitment
We built Everwood Reserve around a simple conviction:
Excellence in residential care means going beyond the basics of medication management and ADL support.
It means paying attention to the nutritional, cognitive, and physiological factors that determine whether residents truly thrive — not merely survive.
Vitamin D is only one piece of that picture.
But it is a piece too often overlooked in homes and clinics alike.
Every resident is an individual, and their care should reflect that.
Not another number in a nursing home.
Joseph Rasberry, PA-C
References
- Huang Y, Chen Y, Wu Y, Dai X, Feng J, Li X. Association of vitamin D with risk of dementia: a dose-response meta-analysis of observational studies. Front Neurol. 2025;16:1649841.
- Liu Y, Zhong Z, Xie J, Ni B, Wu Y. Neuroprotective roles of vitamin D: bridging the gap between mechanisms and clinical applications in cognitive decline. Neurology. Published April 2026.
- Lönnroos E, Ylilauri M, Lamberg-Allardt C, et al. Effect of vitamin D3 supplementation on the incidence of diagnosed dementia among healthy older adults. J Gerontol A Biol Sci Med Sci. 2025.
- Stafford M, Cooper R, Cadar D, et al. The prevalence and determinants of vitamin D status in community-dwelling older adults. Nutrients. 2019.
- Salari N, Hassanabadi M, Khaleghi AA, Mohammadi M. The global prevalence of vitamin D deficiency in the elderly: a meta-analysis. Indian J Orthop. 2024.
- di Filippo L, Terenzi U, Giustina A. Vitamin D in the elderly: preventing bone, muscle, and adipose deterioration. Arch Endocrinol Metab. 2025.
- Amrein K, Scherkl M, Hoffmann M, et al. Vitamin D deficiency. StatPearls. Updated February 2025.
