If humans were sun-basking cats, we could have possibly protected ourselves from several health conditions, primarily vitamin D deficiency. With an increasing number of people working indoors, vitamin D deficiency has taken a toll on people’s health, studies show.
Scientists have long established that sunlight is essential for the production of vitamin D, which is necessary for strong bones and muscles, as well as for immunity. However, we can characterise the deficiency as a modifiable risk, as we can address it with supplements.
In a recent study published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, a team of researchers found that taking vitamin D supplements was associated with living dementia-free for longer periods. The team observed 40 per cent fewer cases of dementia in supplement takers than in those who did not take them.
“We hypothesised that exposure to any type of vitamin D supplement would be associated with lower dementia incidence,” according to the paper.
The deal with vitamin D
Vitamin D is not readily available in the body. One form, Vitamin D2 (ergocalciferol), is derived from plant-based foods. The other form, Vitamin D3 (cholecalciferol), is produced in the skin cells on exposure to ultraviolet B rays. Both these forms are pivotal for the absorption of calcium in the body.
It is well known that calcium is vital for bone health; however, what is not that well known is  it is also a crucial element for neuron communication. Therefore, doctors commonly advise supplements to address vitamin D deficiency based on the levels in the blood.
“Our findings give key insights into groups that might be specifically targeted for vitamin D supplementation. Overall, we found evidence to suggest that [starting vitamin D] supplementation might be beneficial before the onset of cognitive decline,” professor Zahinoor Ismail of the University of Calgary and the University of Exeter, who led the research, said in a statement.
Dr Miller cautions that awareness of prior vitamin D status and doctor-prescribed dosage of supplements is important.
Analysing the numbers
To understand the relationship between vitamin D supplements and the onset of cognitive decline, the team screened the medical information of 12,366 dementia-free participants, with an average age of 71, from the US National Alzheimer’s Coordinating Centre.
Of these, 4,637 participants took vitamin D supplements – either calcium–vitamin D, cholecalciferol, or ergocalciferol. In addition, the participants were tracked for 10 years and monitored for dementia.
The number of participants who took supplements before being diagnosed with dementia was recorded to get an accurate picture.
The researchers from the University of Calgary’s Hotchkiss Brain Institute, Canada and the University of Exeter noted:
- 74.8 per cent of the 2,696 participants who were diagnosed with dementia in the interim 10 years had no exposure to vitamin D supplements
- The positive effect of the supplement on cognitive health was greater in women
- The supplement had a more significant effect on people who did not carry the APOE4 gene, compared to those who carried the APOE4 gene (mutations in APOE4 are identified as a high-risk factor for Alzheimer’s)
Dr Joshua W Miller, Rutgers, The State University of New Jersey, USA, puts his team’s observations into context. “If one is destined to become demented in five years, with all else being equal, taking vitamin D supplements may extend the time without dementia to seven years. That would mean two extra years one would have with family and friends before the disease makes one profoundly impaired,” he said.
Read more: Decoding the genetics of Alzheimer’s: the role of APOE4 and SHMOOSEÂ
Future directions
The study provides a good beginning for a clearer understanding of the impact of vitamin D supplements in delaying dementia. However, certain limitations need to be addressed, such as other health conditions, lifestyle factors, and unbiased reporting of vitamin supplement use. The researchers indicate that future trials would factor in sun exposure, ethnicity, and whether it influences the onset of dementia.
“The ongoing VitaMIND study at the University of Exeter explores this issue further by randomly assigning participants to either take vitamin D or [a] placebo and examining changes in memory and thinking tests over time,” according to co-author Dr Byron Creese from the University of Exeter, Â in the statement.
As vitamin D accumulation in the body can become toxic. Dr Miller cautions that awareness of prior vitamin D status and doctor-prescribed dosage of supplements is important.
“My suggestion is that if you decide to take vitamin D supplements, doses of 1000 or 2000 IU per day are a reasonable recommendation. Something to consider would be to have your doctor measure your vitamin D status before you start taking supplements and then again after several months. This would tell you if the dose you are taking effectively improves your status,” said Dr Miller.
Read more: How ‘hidden hunger’ influences cognitive decline in the elderly
