As days darken, vitamin D can be our defence against illness

SOMETIMES, on a blue sky, crisp morning in October, I will make the bold statement that “autumn is my favourite season of the year”.

Forgetting how happy I am to see daffodils in spring, or the long, warm evenings of summer, a pile of crunchy russet and yellow leaves convince me that this is the best time of the year.

My birthday is in October, so maybe thoughts of presents cloud my judgement. I forget that the season of conkers and scarlet leaves heralds the approaching season of coughs and snot.

A respected climate scientist recently described the barmy, balmy September and October temperatures as “absolutely gobsmackingly bananas”, so it has been almost a relief to see the temperature dial drop to more normal ranges in the last week.

Two more weeks and the clocks will go back, and we will be heading for the dark days of winter. 

Already, there are bus shelter advertisements warning us to get “winter-ready”, with pictures of various paracetamol-laced potions you can try when the lurgy hits.

But, as we know, prevention is better than cure, and many scientists think that, instead of dosing ourselves once an infection has lodged in a lung, upping our vitamin D levels could boost our immune system and help us better ward off the onslaught of winter bugs and viruses.

We are so (rightly) attuned to protecting ourselves from the damaging effects of the sun to avoid cancer and ageing, that we do not often think of the sun as a critical part of our immune system, but our bodies require sunlight to make vital vitamin D.

Yes, the so-called ‘sunshine vitamin’ is present in some foods like oily fish, red meat, and egg yolks, but the primary natural source of vitamin D is made in our skin.

When skin is exposed to sunlight, the energy from the rays interacts with a molecule that is naturally present in our skin and causes a photochemical transformation to Vitamin D3. Once it is formed, it enters the bloodstream, travels to the liver and kidneys, where it is further modified to provide for different essential processes in the body.

However, in Ireland, 50% of adults are deficient in vitamin D in winter months. Worldwide, an estimated one billion people have inadequate levels of vitamin D in their blood.

People with darker skin living in northern latitudes are more susceptible to vitamin D deficiency because dark skin contains more melanin, a natural pigment that protects from harmful UV radiation from the sun.

Melanin stops the radiation penetrating the skin, and as a result people with darker skin need more sun exposure to produce sufficient vitamin D.

For people with dark skin living in countries like Ireland, where sunshine is in short supply for six months of the year, supplementation of vitamin D is especially important. And for people like me who are pure bán, hide from the sun and wear sunscreen year-round for fear of burning, and spend large parts of their waking days chained to a desk, supplementation is a smart idea too.

Vitamin D’s significant role in bone and teeth health and in the immune system has long been understood, but the Covid-19 pandemic focused the attention of public health doctors on the influence of vitamin D deficiency on outcomes for Covid-19 patients.

Back at the start of the pandemic, doctors noticed that many of the earliest admissions to hospital - frail nursing home residents and people with obesity - were severely deficient in vitamin D.

The higher rates of death for hospital workers with dark skin may also have been linked to vitamin D deficiency.

Irish researchers in TU Dublin have recently published a number of papers looking at links between vitamin D deficiency and risks of Covid-19, and say there is now a wealth of data which show that low vitamin D levels significantly increase the risks associated with Covid-19.

There are numerous studies which show that supplementation both before and during hospital admission helps to reduce these risks.

Daniel McCartney and his colleagues’ studies suggest that, compared with individuals who are replete with vitamin D, those with low vitamin D levels are 1.5 to 2 times more likely to develop symptomatic Covid infection, are more likely to be hospitalised with Covid-19, are more likely to be admitted to ICU once hospitalised, are more likely to require ventilation during their admission, and are also more likely to die from Covid-19 during their admission.

Many experts think increased vitamin D supplementation is required for avoiding the worst of Covid-19 infection outcomes and for improving population health overall.

Vitamin D has protective effects against cancer mortality, heart failure, diabetes, and dementia, but there is scientific debate about how much people need each day and what the optimal levels should be to prevent disease.

In Ireland, healthy adults of fair-skinned ethnicity are advised to take 15 micrograms from October to March, and adults of dark-skinned ethnicity are advised to take that amount throughout the year.

The TU Dublin researchers believe that a higher dose is required and recommend that the “vitamin D supplement dose required by Irish adults to achieve both bone health and enhanced immune coverage against Covid-19 and other respiratory pathogens is 20-50 micrograms/day”

Considering the stresses on our health system, it would appear prudent to fully explore how a low cost vitamin supplement could positively impact the overall health of the population and reduce disease and hospital admissions.

At the very least, a public health campaign about taking a vitamin D supplement during the winter months could keep a few people off trolleys.