Vitamin D – are you getting enough of the sunshine vitamin?

 As we head into winter here in New Zealand, it felt like an important time to talk about vitamin D. As our main natural source of vitamin D is from sunlight on our skin, the winter months when UV rays aren’t as strong, are when we are at the greatest risk of deficiency.

While we can get small amounts of vitamin D from animal foods such as oily fish, egg yolks, shitake mushrooms and some dairy products, it is not enough to maintain optimal levels of this important vitamin.

Why is vitamin D so important?

Vitamin D is not actually a vitamin. It’s a hormone, and almost every cell in your body has a vitamin D receptor (the part of the cell that vitamin D attaches to), so that in itself tells us it’s a pretty big deal! We’ve known for a long time that vitamin D is important for bone health because it helps us absorb calcium, but there is now a significant amount of evidence linking vitamin D deficiency to many health conditions including type 2 diabetes, heart disease, skin conditions and even some cancers.

Vitamin D also has a key role in immune function, with deficiency linked to the development of autoimmune conditions such as Hashimoto’s and Rheumatoid Arthritis as well as increased risk of infection. In fact there has been a lot of focus on vitamin D and Covid-19 with numerous studies showing increased severity of symptoms in those with lower levels.

Vitamin D and Mental Health

More and more research is also showing a link between low levels of vitamin D and an increased risk of depression and anxiety.

There are vitamin D receptors throughout the central nervous system so that’s a big clue that Vitamin D is essential for brain health! It can stimulate brain derived neurotrophic factor (BDNF) which promotes the survival of nerve cells in the brain. It can act as an antioxidant and have anti-inflammatory effects in the brain, and we know that inflammation is implicated in depression and anxiety. And low levels of vitamin D may also impact levels of key neurotransmitters that help regulate mood and emotions such as serotonin, dopamine and adrenaline.

Who is at risk?

Several factors affect vitamin D status and there are some specific groups who are at greater risk:

The elderly – our skin is less efficient at synthesising vitamin D as we age and older people who may be frail and less mobile also tend to spend more time indoors

Those with darker skin – as they have higher amounts of the pigment melanin which reduces the skin’s ability to absorb and produce vitamin D from sunlight

Those with obesity – as vitamin D is a fat soluble vitamin it can get stored away in fat cells rather than being released into circulation for use. Those with an increased number of fat cells may therefore need larger doses to reach optimal levels

People with fat malabsorption – vitamin D needs some dietary fat for absorption. Those on low fat diets or with health conditions that affect the absorption of fat (such as Crohn’s or Coeliac disease) may be at increased risk

Those with chronic illnesses – such as liver or kidney disease as both organs play an important role in the conversion of vitamin D to its active form

People who don’t get enough sun exposure – whether it’s working shifts and not having the opportunity, covering up for occupational or cultural reasons, or deliberately avoiding the sun because of the skin cancer risk, some of us just don’t get enough sunlight exposure

What is an optimal level?

In New Zealand a blood level of vitamin D below 25 nmol/L is considered moderate to severe deficiency, 25-50 nmol/L is considered mild deficiency and between 50-100 nmol/L is considered optimal. Though some experts suggest that levels above 75 nmol/L are ideal.

It is estimated that almost 50% of New Zealanders have vitamin D levels below 50 nmol/L, which aligns with global deficiency rates, so it may be worth considering supplementation. As vitamin D is fat soluble, it can get stored in fat cells and is not easily excreted from the body. Whilst toxicity is rare, it is worth getting your levels tested before supplementing to ensure you are not taking a larger dose than needed.

Vitamin D needs friends!

In order to do its job properly in the body, vitamin D needs a little help from other key nutrients. Vitamin K helps regulate the amount of vitamin D made by the body, ensuring it has enough but not too much. Magnesium helps the body use vitamin D, boron increases blood levels of vitamin D and zinc and vitamin A support vitamin D receptors.

It’s therefore important you are not only getting enough vitamin D, but also adequate amounts of these other nutrients, either through diet or supplementation, to get the most out of it.

How to support your vitamin D levels

• Aim to get 10-20 minutes of sun exposure, without sunscreen, every day (obviously being careful not to burn)
• Include foods containing vitamin D in your diet (oily fish, egg yolks, shitake mushrooms, dairy)
• Get tested to understand your vitamin D levels so if supplementation is required, the dosage and duration can be personalised to your specific needs
• Ensure you are also getting sufficient levels of the nutrients needed to support vitamin D

Aside from topping up our vitamin D levels, getting outdoors in natural light has so many other benefits for our mental health, so let’s enjoy this beautiful winter sunshine while it lasts!