NMU 358 – Vitamin D’s Preventive Role in Alzheimer’s disease Strengthened by Experimental and Human Prospective Studies

Nutrition/Natural Medicine Update No 358 (June 4, 2025)

with Dr. James Meschino

Topic: Vitamin D’s Preventive Role in Alzheimer’s disease Strengthened by Experimental and Human Prospective Studies

Source: Journal of Brain Science (2021)

Several human prospective studies in recent years have shown that higher blood vitamin D levels are associated with a significant reduction in risk of developing Alzheimr’s disease. For example, in 2014 Littlejohns et al, published their findings showing that individuals with a blood vitamin D level (25-hydroxycholecalciferol) below 25 nmol/L (10 ng/ml) had a two-fold risk of developing Alzheimer’s disease over the ensuing 5.6 years of follow-up, compared to individuals who had a blood vitamin D level above 50 nmol/L (20 ng/ml). They studied 1658 older individuals during the study period. In 2017, The Rotterdam Study, published in the Journal Alzheimer’s disease, also showed that lower vitamin D blood levels in individuals over 55 (yrs old) was associated with an increased risk of developing Alzheimer’s disease over the 15-year follow-up period. Experimental and animal model studies have demonstrated the mechanism through which vitamin D has been shown to help prevent Alzheimer’s disease.

As brilliantly outlined in the Journal of Brain Science (2021), the brain shows the ability to receive vitamin D from the bloodstream and to produce some of its own vitamin D. Brain cells convert vitamin D into its most active form, which is 1,25-dihydroxy vitamin D (calcitriol). In the brain this form of vitamin D has been shown to enhance the ability of brain immune cells, called macrophages, to ingest and clear beta-amyloid plaque. Beta-amyloid plaque is a hallmark feature of Alzheimer’s disease. In fact, macrophages derived from patients with existing mild cognitive impairment and Alzheimer’s patients show enhanced capability to eliminate amyloid plaques after treatment with 1,25 dihydroxy vitamin D. In mice that are bred to develop amyloid plaque and Alzheimer’s disease (transgenic mice) a vitamin D-enriched diet was shown to decrease the amount of beta-amyloid plaque accumulation to a significant degree.

Other studies show that vitamin D is also required to stabilize the amyloid protein precursor, helping to prevent its transformation into beta-amyloid plaque. Vitamin D has also been shown to play a role in suppressing brain inflammation and reducing free radical damage to brain cells (reducing oxidative stress), which are two other mechanisms shown to be helpful in preventing Alzheimer’s disease and other neurodegenerative diseases.

In my view, there are many reasons to maintain optimal vitamin D blood levels. Optimal vitamin D status is required to help prevent osteoporosis and various studies have shown its importance in the prevention of some cancers and possibly some autoimmune diseases. Optimal vitamin D status is also critical to support immune health, helping to prevent virulent infections, most notably respiratory tract infections like COVID-19 and pneumonia. But vitamin D is also required for brain health and shows impressive mechanisms involved in the prevention of Alzheimer’s disease. Human prospective studies clearly show that better vitamin D status is associated with a decreased risk of developing Alzheimer’s disease. For all these reasons you should ensure that your blood vitamin D level is above 50 nmol/L (30 ng/ml) and more ideally above 78-85 nmol/L (30 – 34 ng/ml) (but below 150 nmol or 60 ng/ml)) to get the full health benefit of vitamin D.

It may interest you to know that in Canada approximately 32% of people have vitamin D levels below 50 nmol/L (30 ng/ml) and 20% of the US population have vitamin D levels as low as 30-49 nmol/L. (reference #2)Most people can achieve an ideal blood vitamin D level by supplementing with 1,000 – 2,000 IU per day. (reference #3)

I have provided the references for this information in the test below.

Reference:

1. Main Reference: Bivona G et al. The rôle of vitamin D as a biomarker in Alzheimer’s disease. Brain Science. 2021; 11(3): 334

The Role of Vitamin D as a Biomarker in Alzheimer’s Disease – PMC

2. Amrein K et al. Vitamin D deficiency 2.0 : An update on the current status worldwide. Fur J Clin Nutr. 2020; 74(11): 1498-1513.

https://pmc.ncbi.nlm.nih.gov/articles/PMC7091696/#:~:text=Prevalence%20rates%20of%20severe%20vitamin,2%2C%2017%E2%80%9319%5D.

3. Dedeckova E et al. Vitamin D3 Supplementation : Comparison of 1,000 IU and 2,000 IU dose in healthy individuals. Life (Basel). 2023;16(3): 808.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10053989/

Eat Smart, Live Well, Look Great,
Dr. Meschino