Alzheimer’s disease is linked to vitamin deficiencies
Although the development of Alzheimer’s disease is complex, evidence suggests that vitamin deficiencies play a significant and often overlooked role. This is especially true for vitamin C, which supports neuronal health in multiple ways. Deficiencies in vitamin D, certain B vitamins, vitamin A, and vitamin E also play important roles through various mechanisms. A large meta-analysis comparing vitamin levels in Alzheimer’s patients and healthy individuals found that those with Alzheimer’s had significantly lower levels in the blood.
Alzheimer’s disease is the leading cause of dementia and imposes a huge personal and socio-economic burden. The disease stems from failing brain function as nerve cells in key brain regions gradually die. Researchers have identified accumulations of beta-amyloid and tau proteins that displace healthy cells and lead to symptoms such as memory loss, disorientation, and cognitive decline. It is also believed that brain insulin resistance contributes to Alzheimer’s; people with type 1 and type 2 diabetes face a higher risk, and the disease is sometimes referred to as “type 3 diabetes.”
Overall, Alzheimer’s is characterized by inflammation and oxidative stress in the brain, where free radicals damage neurons and trigger programmed cell death (apoptosis). The disease progresses slowly, and most patients die 7-10 years after being diagnosed with the condition.
Given the rising number of cases and the large impact of diet and lifestyle, the researchers behind the meta-analysis wished to investigate different vitamins’ roles in prevention and adjunct treatment. They trawled PubMed, Web of Science, MEDLINE, and other databases for studies comparing blood vitamin levels in Alzheimer’s patients and healthy controls. Based on 67 published papers, the analysis showed significantly lower vitamin C levels in Alzheimer’s patients, with notable deficiencies also in vitamin D, folate (B9), B12, vitamin E, and vitamin A.
The researchers conclude that these findings shed new light on the potential role of vitamin deficiencies in Alzheimer’s disease progression. The meta-analysis was published in the Journal of Human Nutrition and Dietetics. It also highlighted that different vitamins contribute to brain health in unique ways:
Vitamin C and brain health
The brain contains more vitamin C than any other organ, yet its neuroprotective role is underestimated. Vitamin C is well known for collagen formation in connective tissues, which includes brain tissue. It also supports the development and differentiation of neurons, as well as myelin formation, all crucial for cognitive function. Additionally, as a powerful antioxidant, it shields neurons from chronic inflammation and oxidative stress. Vitamin C is water-soluble and found in citrus fruits, vegetables, and berries. Research shows that about 15% of people in Western countries - especially older adults, smokers, and those socially disadvantaged - are deficient. The daily recommendation (RI) is 80 mg to prevent scurvy, but some researchers suggest more may be needed for optimal brain health.
B vitamins and brain health
B vitamins are essential for energy metabolism and nervous system function. Deficiencies in vitamin B12 and folate (B9) seem to raise Alzheimer’s risk, likely due to their role in regulating homocysteine, which is a metabolic byproduct. High homocysteine levels can trigger oxidative stress and inflammation, damaging neurons and blood vessel linings. B vitamins are predominantly found in whole grains, green produce, and animal products (for B12). Deficiencies often stem from poor diet, low stomach acid, heavy alcohol use, or certain medications (e.g., acid blockers, antibiotics, and metformin). Supplements are an option: B-complex tablets and sublingual B12 can help, especially in cases of poor absorption, while severe deficiency may require injections.
Vitamin D and brain health
Vitamin D regulates various genes and metabolic processes. Brain regions such as the hippocampus that is crucial for memory have vitamin D receptors. The vitamin helps control inflammation and oxidative stress in the brain and may prevent the buildup of harmful proteins linked to Alzheimer’s. At northern latitudes, sunlight is our main source of vitamin D. Although daily recommendations (RI) are 5-20 µg, actual needs may be higher due to genetics, age, and body weight. A meta-analysis in Nutrients suggests that 50 µg daily may prevent deficiency in most adults.
Vitamins A and E and brain health
Vitamins A and E are fat-soluble antioxidants that protect nerve cells from free radical damage and oxidative stress. Vitamin A (retinol) comes from animal products like liver, eggs, butter, and fatty fish, while provitamin A (carotenoid) is found in carrots, tomatoes, and peppers. Vitamin E is found in nuts, seeds, avocado, leafy greens, and unrefined oils.
In summary:
- A diet lacking in certain vitamins is linked to Alzheimer’s.
- Nutrient intake (including from supplements) can be key for prevention and overall brain health.
References:
Sagar Marwaha et al. Unlocking the Vitamin Puzzle: Investigating Levels in People With Alzheimer´s Disease Versus Healthy Controls Through Systematic Review and Network Meta-analysis. Journal of Human Nutrition and Dietetics. 2025
K. Chaudhari et al. Vitamin C supplementation, APOE¤ genotype and cognitive functioning in a rural-dwelling cohort. The Journal of Nutrition, health and ageing. 2016
Chi-Ping Ting et al. Diet Pattern Analysis in Alzheimer´s Disease Implicates Gender Differences in Folate-B12-Homocystein Axis on Cognitive outcomes. Nutrients 2024
Li-Ju Chen et al. The associations of serum vitamin D status and vitamin D supplements use with all-cause dementia, Alzheimer´s disease, and vascular dementia: a UK Biobank Based prospective cohort study. The American Journal of Clinical Nutrition. 2024
Pawel Pludowsky et al. Vitamin D Supplementation: A review of the Evidence Arguing for a Daily Dose of 2000 International Units (50 µg) of vitamin D for adults in the General Population. Nutrients 2024
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