"How could you be that tired at 21?"

Vitamin D deficiency is a lot more prevalent in the colder months - and it's a lot more common than you think. New research from Trinity College Dublin has shown that Vitamin D deficiency is widespread across Dublin and its surrounding areas, with 1 in 6 people being deficient all year round, rising to 1 in 4 in the winter. The study, part funded by MISA and Avonmore, also showed that young people aged between 18 and 39 had the lowest recorded levels of Vitamin D in the area. Niamh Mitchell was diagnosed with Vitamin D deficiency in her early 20s. Young, fit, and a regular taker of multivitamins, the Leixlip-born woman couldn't figure out why her immunity was dipping so significantly.

“I was just wrecked all the time," she tells Her. "Ridiculously wrecked. It was 3pm in the day and I’d be exhausted, like I could go straight to bed.

"I was getting muscle cramps, which isn’t something I’d ever have suffered from. It just didn’t make sense to me. How could you be that tired at 21?"

Niamh went to the doctor and got a blood test. Presuming her exhaustion was to do with her iron levels, she was surprised when her results came back stating Vitamin D deficiency. Levels of 30nmol/ml and lower tend to indicate a person is lacking in the sunshine vitamin. In Niamh's case, her reading came back at around 12 or 13 - levels low enough that she was given a prescription to increase her intake.

"You can get over the counter supplements but I needed a much bigger dose," she says. "I also had a whole list of foods I needed to introduce into my diet, and had to make sure I was getting 20 to 30 minutes of sunshine per day.

"I didn’t really think the changes would have much of an impact. I thought, ah yeah I’ll have a bit more fruit and veg, but it started working immediately."

Within a couple of weeks, Niamh was a new woman. Her energy was back, her mood was better, and her muscle cramps had stopped. She stayed on supplements for most of the year, trying to get out in the sun as much as possible. During pre-Covid times, she'd make sure that she had a getaway or two planned leading into the winter months, to make sure that she was getting her fill from somewhere. "I’m always joking saying I need to go away for a bit of the Vitamin D, but it's true!" she says. "It's the lack of sunshine where we live. "In Ireland, it's so common. Most people just don't even know it's a thing. The doctor I went to was saying it’s crazy the amount of people who come in and say they’ve never even heard of Vitamin D deficiency. They’re so surprised. "I always thought taking a multivitamin would cover me, but clearly not. I’d say the majority of my friends and family are lacking in Vitamin D too, they just haven’t been tested.” Now, Niamh pretty much has a handle on her Vitamin D deficiency. As the summer months come to an end, she feels her mood start to dip, her energy levels start to drop, and she knows she needs to get back on her supplements. The lack of travel amid the pandemic, she says, triggered her symptoms a lot earlier this year. "It has hit me harder," she says, "so I’ve really had to really keep an eye."

"Given everything that’s going on at the moment, it’s really not that rare to feel low energy. But once I went to the doctor it made total sense for me."

So, what steps can you take to increase your Vitamin D intake? The first step is to get more sunshine - a feat that may prove difficult in Ireland, but an important one all the same. Similarly, you can get yourself some Vitamin D supplements from the pharmacy or any health food shop. There are also a selection of specific foods that are good for those lacking in the sunshine vitamin. TCD's nutritionist Helena Scully advises the best food sources for Vitamin D are:

• Oil fish, including salmon, mackerel and herring
• Egg yolk
• Fortified foods, like Vitamin D fortified milk and cereals

If you're concerned about your Vitamin D intake, you can purchase supplements in most pharmacies, or ask your doctor for a blood test.