Recently, U.S. researchers have established a link between vitamin D intake and higher cognitive scores in people showing early signs of cognitive decline. For the authors, high-dose intakes could protect the brain from the earliest stages of dementia.
What is vitamin D?
To recall, vitamin D is an essential substance for the body that, in fact, behaves like a hormone. Unlike other vitamins that come solely from our diet, it has the particularity of being synthesized by the human body under the action of ultraviolet rays (UV-B) from the sun on the skin. Primarily, vitamin D positively influences bone and dental health, the immune system, and muscle function.
Note that vitamin D from sun exposure is referred to as D3, just as the form from animal-derived products such as fatty fish, cod liver oil, egg yolk, and dairy products and butter. There is also the so-called D2, which appears in plant-based sources, namely certain mushrooms, avocado, and dark chocolate. Naturally, this substance is found in a wide range of dietary supplements to prevent or correct deficiencies.
A meaningful improvement when the dosage exceeds recommendations
An Emory University team (United States) conducted a study involving 54 adults with sleep disorders and mild cognitive impairment. According to the results, high-dose vitamin D may play a protective role against dementia. These findings, slated to be published in Sleep Medicine in October 2026, could shift medical perceptions of vitamin D, particularly regarding the prevention of neurodegenerative diseases.
In reality, the researchers observed a significant improvement in cognitive abilities among participants taking more than 5,000 IU per day. This amount is higher than the usual recommendation, which stands at 4,000 IU per day. Moreover, the scientists quantified this improvement using the Montreal Cognitive Assessment (MoCA), a quick screening tool that health professionals use to detect mild cognitive impairment early. For the authors, the benefits are especially pronounced when intervention occurs at the early stages of decline, before the onset of advanced dementia. These findings thus suggest that vitamin D is a preventive option very easy to implement in the face of rising Alzheimer’s cases and, moreover, fairly inexpensive.
« To our knowledge, this is the first study assessing the link between vitamin D supplementation and global cognitive function in people who simultaneously suffer from sleep disorders and mild cognitive impairment. Our results suggest that higher daily vitamin D supplementation is associated with better overall cognitive performance in this population.
How does vitamin D protect the brain?
It should be noted that the brain contains numerous vitamin D receptors, notably in the hippocampus — the region playing a crucial role in memory. The data show that the substance acts as a shield, thanks to several actions. The first is anti-inflammatory and antioxidant, since vitamin D safeguards neurons against chronic inflammation, a key factor in the development of neurodegenerative diseases.
Additionally, prior research has demonstrated that good vitamin D levels in midlife can reduce the accumulation of the tau protein, responsible for the characteristic lesions of Alzheimer’s disease. Also, vitamin D participates in the synthesis of dopamine and serotonin and thus helps preserve neurotransmitters.
