Vitamin D from sunshine could help keep dementia at bay, a study shows, and fight other diseases

Vitamin D has been known for its links to bone health and strengthened immunity; a study suggests it could also help protect the brain and lower dementia risk
While some foods naturally contain vitamin D, particularly mushrooms, most of us can get as much of this nutrient as we need from exposure to sunlight

Wellness

Anthea Rowan

Published: 4:15pm, 8 Jul, 2022

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What does vitamin D bring to mind? Sunshine? Bone health? A boost to immunity?

Foods in supermarkets on promotion at the height of the coronavirus pandemic bore labels that boasted of their high vitamin D levels – specifically mushrooms which, exposed to ultraviolet light, deliver significant amounts of vitamin D2.

This fat-soluble vitamin has been touted in recent years as being good for us in a slew of ways, from safeguarding bone health to bolstering immunity. Laboratory studies show that vitamin D could even reduce cancer cell growth, help control infections and reduce inflammation.

A recent study suggests vitamin D could offer another huge benefit: it could help to protect the brain from deterioration and the diseases that come with that – including dementia.

Just a few minutes of sunshine a day can ensure you achieve required vitamin D levels. Photo: Shutterstock

In 1928, German chemist Adolf Windaus was awarded the Nobel Prize for his explanation of the structure of vitamin D, which could then be chemically synthesised for the first time a decade later.

But this important little nutrient had had a long history even before Windaus. Rickets, the bone disease caused by vitamin D deficiency, had been recognised for more than 200 years and was first described in medical literature in 1650.

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The origin of the word rickets is an interesting one. One hypothesis is that it derives from “to rucket”, or to breathe with difficulty. Or from the Anglo Saxon, “wrikken”, to twist. Because most of the words seemed to derive from England, rickets was sometimes called “the English disease” – after the island that gets too little sunshine.

Professor Elina Hypponen is a professor in nutritional and genetic epidemiology at the University of South Australia and director of the Australian Centre for Precision Health – and the lead researcher of the new study.

She notes that “we are strongly dependent on vitamin D intakes from sunlight, which in turn depends on many factors, including season, the location where one lives, and even our skin colour, as melanin in the darker skins acts as a very powerful sunscreen and can block vitamin D synthesis”.

Professor Elina Hypponen is professor in nutritional and genetic epidemiology at the University of South Australia. Photo: Professor Elina Hypponen

Vitamin D – which is technically a hormone – is important for overall health, she stresses.

“It has many effects on the normal functioning of the body. For example, we have recently shown that the same type of severe deficiency that increases the risk of dementia is also associated with greater low-grade inflammation and heart disease risk.”

There are treatments, and cures, for inflammation, heart disease, even many types of cancer now. But dementia? There’s no cure for that. Measures to prevent it are all we have.

Vitamin D is important for overall health. Photo: Shutterstock

Hypponen’s study, the largest of its kind to date, which involved over 300,000 participants, was inspired, she says, because “it has long been suspected that vitamin D receptors which mediate the effects of the active hormone are present in the human brain, and as a result it may have implications for the development of neurocognitive diseases such as dementia”.

Firstly, the presence of vitamin D receptors in the hypothalamus suggests that active vitamin D promotes the growth and maturation of neurons – the information transmitters in the brain.

Secondly, active vitamin D has been associated with reduced blood clotting and with regulation of the system that affects blood pressure – which provides protection against stroke, which can be a catalyst for dementia.

Fresh products rich in vitamin D. Eating them alone will not give you enough vitamin D. Photo: Shutterstock

Thirdly, vitamin D may support brain health by reducing inflammation related to neurovascular damage, and possibly reduce amyloid proteins, which are commonly seen in Alzheimer’s disease and may contribute to disease development.

This is encouraging given the prognosis for dementia is death, and a slow painful one at that. But how do you know if you’re getting enough vitamin D?

Hypponen says diet is a poor source of vitamin D; while some foods such as oily fish, eggs, and milk contain some vitamin D, it is practically impossible to get enough from food unless the diet also includes food products that have specifically been fortified with vitamin D.

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Low levels of vitamin D in the human system are defined as 25 nanomoles per litre (nmol/L) – and your levels are easy to check with a simple blood test.

A test is not always needed, she says. People with active lifestyles, and who regularly go outdoors during sunlight hours, are likely to have adequate vitamin D levels much of the year. During the darker winter months, a simple over-the-counter vitamin D supplement can help to keep those levels up.

You should be aiming for 50 nmol/L or higher, she says.

Supplements can ensure you get enough vitamin D in seasons when sunlight is limited. Photo: Shutterstock

“We saw the strongest effects on dementia risk with participants who had very low concentrations (less than 25nmol/L). There was a slight increase in risk for individuals who were in the 25-50 nmol/L range, but most of the benefits, according to our modelling, appeared to have been reached when levels were 50 nmol/L or higher.”

So, during those bleak winter months, what should you be taking to reach that level?

The UK’s National Health Service (NHS) suggests 10 micrograms a day will be sufficient for most people, and urges adults not to take more than 100 micrograms (4,000 IU) a day. The safe dose for children is much less.

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Not everybody can take vitamin D supplements and taking very high doses can be harmful, as it may lead to a build-up of calcium in the body – hypercalcaemia – which, paradoxically, can weaken bones and damage major organs like the heart and kidneys.

The NHS says you cannot overdose on vitamin D through sunlight exposure. But you can burn. So cover up and protect your skin with a high SPF sunblock. Luckily, during the summer most people only need to stay in bright sunlight for a few minutes a day to get enough vitamin D.

How significant is Hypponen’s research? It suggests that preventing vitamin D deficiency in the population would help to reduce dementia risk, as well as avoidable risks of many other diseases, she says.

Given that dementia is a global issue, with the numbers of sufferers set to rise to 50 million in the next decade, this is sunny news indeed.

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