A new study by Taiwan’s National Health Research Institutes (NHRI) has found that extended use of vitamin D supplements could make older adults up to 80 percent more likely to develop Alzheimer’s and double the risk of death among those who already have the disease.
The new findings, which challenge the long-held consensus that vitamin D is broadly beneficial to brain health, were presented at a press briefing Monday by research team leader J.L. Juang (???) of the NHRI’s Institute of Molecular and Genomic Medicine.
According to Juang, epidemiological studies have long linked vitamin D deficiency to a higher risk of Alzheimer’s disease and other forms of dementia, but have not clearly established a causal relationship.
The purpose of his team’s research, he said, was to clarify whether vitamin D deficiency was a risk factor for Alzheimer’s or an outcome caused by the disease.
In its study, the team found that mice with Alzheimer’s given a vitamin D sufficient diet exhibited significantly lower levels of vitamin D in their blood than wild mice, suggesting that the deficiency was an outcome of early-stage Alzheimer’s.
At the same time, they discovered that the mice had higher levels of vitamin D receptors in their brain, particularly in the senile plaques (known as beta amyloid) associated with Alzheimer’s disease, Juang said.
Investigating this latter phenomenon, the team found that beta amyloid triggered the interaction of vitamin D receptors with tumor suppressor p53 in a process that promoted the death of neuronal cells.
As this interaction was strongly enhanced by vitamin D, the researchers concluded that vitamin D could in fact be promoting Alzheimer’s disease.
Given these “surprising” results, Juang said, the team decided to see if they could be validated through research on human subjects.
Using Taiwan’s National Health Insurance Research Database, they found that dementia-free older adults were 1.8 times more likely to develop dementia if they took a 0.25-microgram tablet of calcitriol (the active form of vitamin D3) daily for over 146 days per year.
Meanwhile, older adults with pre-existing dementia were at 2.17 times higher risk of death if taking vitamin D3 supplements, Juang said.
Juang noted that the data was derived from people who had received prescriptions for calcitriol, the active form of vitamin D3, but not the inactive form which is sold over-the-counter, and is “activated” at varying rates, depending on a person’s liver and kidney function.
Juang said the concordant results produced by the team’s animal tests and subsequent human study had “overturned long-term understandings” about vitamin D, but indicated that the vitamin’s other benefits should not be discounted.
Rather, the research should remind older adults that prolonged and high-dose consumption of vitamin D supplements may be detrimental to their brain health, Juang said, adding that more moderate levels of the vitamin could be derived from sun exposure.
The NHRI team’s study on the subject was published last year and most recently on July 12 in the scientific journal Aging Cell.
Source: Focus Taiwan News Channel