We Know Vitamin D Matters. So Why Aren't We Taking It?

6 Min read

In this article:

How many of us are actually low?
Do we get enough from sunlight?
We wanted to learn more, so we asked our Inner Circle
Why it matters
So what's getting in the way?
Insufficient vitamin D doesn’t clearly announce itself
What did our Inner Circle say?
We tested ourselves, too
From knowing to doing

Every autumn here in the UK, we see the advice on vitamin D return: the NHS advises everyone to consider taking a daily 10µg vitamin D supplement during autumn and winter.

It is clear advice. But knowing it doesn’t always mean it becomes part of the day. And this is potentially one contributing factor to why low vitamin D is still so common.

How many of us are actually low?

More than you might think.

The latest National Diet and Nutrition Survey (2019–2023) shows a pronounced seasonal pattern in vitamin D status. Between January and March, 21–38% of people aged 11 and over had blood levels of vitamin D below 25 nmol/L, depending on age and sex.

UK public health guidance uses the 25 nmol/L threshold because the risk of poor musculoskeletal health is considered to rise below it. It’s a population threshold, though, not an optimal target, or something you can work out from how you feel. Vitamin D also contributes to normal immune function, but there’s not yet an agreed blood-level target for immune benefit; other authorities use higher benchmarks, for example, the US National Academies considers 50 nmol/L or above sufficient for most people.

Summer improves the picture considerably. But it doesn't make the problem disappear.

Even between July and September, up to 10% of some age and sex groups were still below 25 nmol/L.

Some people are at greater risk all year round, including those with darker skin and people who rarely get outdoors, which is why the NHS advises these groups to take vitamin D throughout the year.

So this isn't simply a winter story. For some people, the risk extends across the whole year.

Yet, despite all this knowledge, supplement use remains low.

The latest National UK data (2019–2023) found that just 28% of adults aged 19–64 took a supplement containing vitamin D.

Do we get enough from sunlight?

Unlike most nutrients, our main source of vitamin D isn't food. It's sunlight: UVB rays on our skin start the process of making it.

In the UK, from around October to early March, the sun sits too low in the sky for our skin to make enough vitamin D.

And unlike our ancestors, most of us now spend our days indoors.

We wanted to learn more, so we asked our Inner Circle

Population statistics can show us the scale of a problem. They tell us less about what happens on an ordinary dark and dreary October morning when someone is aware of the vitamin D guidance but hasn’t managed to make it part of their daily ritual yet.

So we asked 757 members of our Inner Circle, our community of loyal customers, about vitamin D. This is a self-selected group of our customers, primarily women >40, not a representative sample of the UK.

72% of our community currently take vitamin D.

66% knew about the autumn/winter recommendation.

Yet 15% of those who knew about it still weren't taking vitamin D consistently.

We asked those who weren’t taking a vitamin D supplement why.

31% weren’t sure whether they needed it

27% simply haven’t thought about it

16% believed they get enough from sunlight

This is something we often see in nutritional practice: people can understand a risk and still not feel that the recommended action is relevant, urgent or easy to remember.

Why it matters

We tend to link vitamin D with bones, and it certainly matters there. Vitamin D contributes to the maintenance of normal bones and teeth*, and to the normal absorption and how our bodies use calcium and phosphorus*.

But vitamin D also contributes to:

the maintenance of normal muscle function*
the normal function of the immune system*
a role in the process of cell division*

(*EFSA Authorised Health Claims)

Vitamin D isn't a niche nutrient to think about only when something goes wrong, or just needed for strong bones. It plays a key part in many important functions of the body.

The advice to supplement in the darker months is clear. But advice alone hasn’t closed the the gap.

So what's getting in the way?

Most of us already know our skin's ability to make vitamin D from sunlight falls significantly during the British winter. 66% of our Inner circle were aware.

We already have a national public health recommendation designed to address that gap.

And yet low vitamin D status persists.

So perhaps the next question isn't whether we need more vitamin D advice. It's why so much of the advice we already have never becomes something we actually do.

So we asked the Inner Circle a different question: what would actually prompt you to start taking vitamin D? The most common answer was a blood test showing levels were insufficient (33%). Next was clearer information about whether someone personally would benefit from a vitamin D supplement.

For most people it isn't lack of awareness, but uncertainty about how the public health advice applies to them.

Insufficient vitamin D doesn’t clearly announce itself

The other challenge is knowing the signs that our vitamin D might be low. We are used to responding to signals from our bodies.

Hungry? Eat.

Thirsty? Drink.

Tired? Rest.

Vitamin D status rarely comes with a clear, specific signal. More significant deficiency can affect bones and muscles, but symptoms such as tiredness, aches or weakness are nonspecific and can have many possible causes. How you feel can’t reliably tell you whether your vitamin D level is low. In our Inner Circle, 71% believed tiredness was a sign of low vitamin D. It’s an understandable assumption but can’t reliably tell you your need to supplement.

More significant deficiency can affect bones and muscles, but symptoms such as tiredness, aches or weakness are also nonspecific and can have many different causes.

So rather than trying to diagnose your vitamin D status according to how you feel, the more useful question is whether you have the conditions necessary to maintain it.

Where do you live?
What time of year is it?
How much sunlight reaches your skin?
What does your diet look like?
Are you in a group at greater risk of deficiency?
And are you taking a supplement throughout winter?

What did our Inner Circle say?

75% spend most of their day indoors.

Yet, 89% recognised that spending little time outdoors increases the risk of low vitamin D.

So there’s a gap between knowing that time outdoors matters and the reality for many of us that our jobs and responsibilities mean we are indoors for much of the day.

We tested ourselves, too

Five volunteers from the Ancient + Brave team had their vitamin D levels tested in September.

Five volunteers from the Ancient + Brave team had their vitamin D levels tested in September. All five were lower than we’d have hoped to see after summer, when vitamin D levels are usually near their annual peak.

This raises a question: if levels are lower than we’d like after summer, what might they look like by February, when UK sunlight is too weak for our skin to make vitamin D?

Five people can’t tell us how common low vitamin D levels are. But it’s a familiar picture: office days indoors, and sensible sun protection when outside. Protecting your skin is the right thing to do. It just means sunlight alone may not be enough.

From knowing to doing

Our ancestors lived by the rhythm of the seasons. Modern life keeps most of us indoors, and for half the year the British sun can’t do the job on its own. Spending time outside can support wellbeing in many ways. It just isn’t a reliable way to make vitamin D through the British winter. And this isn’t a reason to seek unprotected sun exposure.

The advice is already there, the hard part is remembering. Pair it with something you already do every morning, like your first coffee or brushing your teeth, and it becomes a ritual rather than a reminder.

Vitamin D is one example of a wider question. We’re good at explaining why health behaviours matter; we spend less time asking what makes them possible in the conditions of real life.