People with darker skins from African, Afro-Caribbean or South Asian backgrounds are nearly four times as likely compared to the Caucasian population to be seriously lacking in vitamin D, according to LiveSmart user data. This is because these individuals have darker skin colour due to the presence of melanin, which reduces the skin’s ability to make vitamin D in response to sunlight exposure. Adults with darker skin are at a high risk of very low levels of vitamin D and therefore deficiency (deficiency is serum levels below 25 nmol/L). Just 5% of our Caucasian users with fair skin were found to have very low levels of vitamin D, whilst other ethnicities were a very worrying 19 per cent.

In addition, 79 percent of LiveSmart users were found to have either deficient or insufficient (insufficiency is 25-50 nmol/L) levels of vitamin D. Interestingly, these individuals were unaware of the problem prior to testing. Despite the raised press profile of vitamin D over recent years, the vast majority of UK adults still aren't getting anywhere near enough.

What's the big deal about vitamin D?
Vitamin D is an essential nutrient that helps regulate the amount of calcium and phosphate in the body, and so contributes to healthy bones and teeth, and strong muscles. There's also a wealth of evidence to suggest that maintaining adequate vitamin D levels can reduce the risk of cardiovascular disease, osteoporosis, cognitive decline and mental health issues, while supporting immune function.

The main natural source of Vitamin D is direct skin exposure to sunlight. It's also found in a small number of foods: oily fish, red meat, liver, egg yolks and fortified foods, such as fat spreads and cereals. The problem? From October to March, the UK sun is rarely strong (or present) enough to have the required effect. And it's almost impossible to get adequate vitamin D through diet: in fact, only around 10 percent of our intake comes from food sources.

Why should employers care?
Anything that compromises the health and wellbeing of your workforce should be a concern. The low mood and lack of energy associated with vitamin D deficiency, for example, will have a knock on effect to the overall wellbeing of your team.

However, the typical office environment – which generally has little or no natural light – is a major contributor to the issue too. For that reason, employers are culpable. The good news, though, is that it's a problem that's relatively easy to solve.

Are supplements the answer?
Back in July 2016, Public Health England issued new guidelines stating that everyone over the age of one should consider taking a daily supplement containing 10mcg vitamin D, particularly during autumn and winter. In addition, people who have a high risk of vitamin D deficiency were advised to consider taking a supplement all year round. This group includes those with darker skins (such as people of African, African-Caribbean or South Asian family origin), as well as pregnant and breastfeeding women, under-18s, over-65s and anyone whose skin has little or no exposure to the sun.

You could well argue that July was an odd time to issue a warning about the dangers of not getting enough sunshine. And to add insult to injury, there have since been no official public health campaigns to hammer the message home – particularly to the high-risk people who should be taking a year-round supplement, among whom awareness is very low. So, if the government isn't going to address the issue, it's time for employers to step in.

Case study: Michelle’s story:
'Throughout the winter months, I've always tended to feel tired and irritable. I knew it was something to do with the season, but never even considered it could be down to vitamin D deficiency until I took a blood test. Since I started taking a daily supplement, I have so much more energy throughout the day. It's inspired me to get my husband and mum tested, too. I just wish I'd known about this years ago!' - Mrs Michelle Desmond-Smikle, 36, Building Manager

What can employers do?
Getting the message across is key here. But we believe one-off campaigns, blanket benefits and initiatives such as 'wellness days' simply aren't enough. To put it bluntly, you can't just stick some fortified foods in the staff kitchen and assume your work is done.

What's needed is a bespoke approach. Employers have a duty to recognise that some of their workforce – black and older workers, for example – are at higher risk of vitamin D deficiency, and to make them aware of this. It's then important to work alongside each individual to address the issue in a way that benefits them.

What else needs to change?
The quest to boost everyone's vitamin D levels should be a sustained and integrated part of company culture. Between April and October, this could be something as simple as encouraging employees to spend more time outdoors: to hold meetings or take phone calls outside, for example, and to ensure that everyone leaves their desk at lunchtime.

And in winter? While it may not be necessary to actually provide vitamin D supplements to the entire workforce, regular reminders of the benefits of taking them are definitely a good idea. It's also worth considering supplying them in a targeted way to high-risk employees. This kind of cost-effective exercise can have a huge impact. Additionally, initiatives that support bone health through a more active lifestyle – subsidised gym memberships or bike hire schemes, could also play a key role.

Ultimately, employers should engage more with their workforce, make an effort to recognise individual risks and needs and continue to monitor the ever-changing data that's available to them through innovations such as LiveSmart in order to build a happier, healthier team.

Further reading: the top 5 signs your staff are struggling with their mental health.