Vitamin D has been getting some increased air time over the past few weeks as its potential role in promoting immunity has come to light.
Despite being a valued member of the vitamin family, vitamin D is rarely the centre of attention. But as my mum always said, ‘every dog has his day’, and even before coronavirus ran rampant and destroyed our social lives, vitamin D was building some social status.
We get most of the vitamin D we need from the sun, which is why historically Australians have never been deficient. But with an increase in skin cancer awareness, and anti-ageing campaigners going wild on the damaging effects of UV exposure to the skin, we’ve all become much more sun conscious.
As a result, way more of us are becoming deficient. What’s interesting is that it’s actually people in their 20’s and 30’s who are at the highest risk, with 1 in 3 of us being deficient. This might be because we’re more likely to work in office jobs, but probably also because we’re hella scared of melanoma and having skin like a leather bag when we’re 40.
For our Northern Hemisphere pals, deficiencies in vitamin D have been more of a concern for a while, mainly due to the lack of sun. Back in the 1930’s, they built these specially made ‘baby cages’ to hang out apartment windows in the UK so the babies could get some sunlight – possibly my favourite invention of the 21st century, I can’t think why these went out of fashion?
What’s the problem with a lack of vitamin D?
So what’s the big deal with vit D and should we be concerned if we’re not getting enough? The problem with vitamin D deficiency is that it can take a long time for signs and symptoms to show up, unlike other vitamin deficiencies where we know pretty quickly.
It was previously thought that the main role of vitamin D was to keep our teeth and bones healthy. Vitamin D is needed for the absorption of calcium from foods we eat, which is important in building and maintaining healthy bones and teeth. If we’re not getting enough calcium through our diet, or enough vitamin D to help absorb that calcium, then our body will start taking the calcium from our bones and teeth which is why they become weakened.
More recently, there’s been a stack more research into other roles that vitamin D plays in the body.
Firstly, deficiencies in vitamin D have been correlated with lowered immunity and higher risk of contracting respiratory viruses. The link here is clear, but this doesn’t mean that vitamin D can improve our immune response, it just means that if we’re deficient, we seem to be more likely to get sick. This basically means that it’s important to make sure you’re not deficient in vitamin D, but taking extra amounts won’t improve your immunity.
Studies have also found links between low vitamin D and higher incidence of depression and anxiety. These links aren’t causal, which means there’s no way we could say that vitamin D deficiency causes depression or anxiety, but it’s an interesting association nonetheless. And this one kinda makes sense given people are much more prone to seasonal affective disorder in areas where there’s less sun. Although again, that could be related to a range of different factors. For example, they found higher rates of serotonin (our ‘happy’ hormone) in post-mortem brains of people who died in summer compared to winter. Moral of the story: we’re just better people in summer.
The other interesting role that’s been researched more recently is vitamin D in preventing preeclampsia and preterm birth. It’s now routine for all pregnant women to have their vitamin D levels checked and supplemented if low.
Finally, research has found a correlation between low levels of vitamin D and some types of cancer, including breast and prostate cancer, and also low levels of vitamin D and dementia or cognitive decline. Again, definitely no way we can say low levels of this vitamin cause these things, but obviously having adequate amounts is important.
Where can we get vitamin D from?
The ‘adequate intake’ recommendation in Australia is 5.0µg/day, with an upper level of intake at 80µg/day, but experts think this level might be largely underestimated.
Ideally, we’d be getting all the vitamin D we need from the sun as this is the best form of absorption, but obviously that’s not always possible. The recommendation for how much sun exposure we need each day to get adequate vitamin D vary greatly depending on where you live and what you’re wearing. Luckily, some genius has simplified this problem for us and created an app to help us work out how long to spend in the sun. The best one I found was QSun which takes your location and tells you how long you can stay out in the sun to get adequate vitamin D without burning – so smart!
Otherwise, there are also foods which are high in vitamin D, so that’s another way we can be getting more. You’ll see almost all of the highest foods in vitamin D are from animal products, except for those sun-baked mushrooms!
Vitamin D in food
- Trout (85g) = 16.2µg
- Swordfish (85g) = 14.1µg
- Salmon, canned (85g) = 12.3µg
- Cod liver oil (1tsp) = 11.3µg
- Salmon, cooked (85g) = 11.1µg
- White fish (85g) = 9.7µg
- Eggs (2 medium) = 8.2µg
- Mushrooms, exposed to UV light (½ cup) = 7.9µg
- Tuna, canned (85g) = 5.7µg
- Sardines, canned (85g) = 4.1µg
- Whole milk (1 cup) = 3.2µg
- Fortified cereals (⅓ cup) = 0.2µg
Interestingly, there’s actually no difference between caged eggs and free range eggs in terms of vitamin D content, but these two different types of hens get their vit D from different places. Caged hens are fed grain fortified with vitamin D, whereas free range hens get their vitamin D from sun exposure. Feels like that choice is a no brainer.
Studies have also found that the vitamin D in fish can get destroyed throughout transit and in storage, with highest amounts being in fresh, market fish.
Finally, how cool is it that mushrooms absorb vitamin D? If you put those bad boys in the sun they’ll be fortified AF.
What about supplements?
You don’t need to get a blood test to diagnose a deficiency before taking a vit D supplement. If you’re in the risqué group, it’s probably best to just be taking one.
So, what constitutes high risk?
- If you follow a plant based or vegan diet
- If you have a darker skin tone
- If you’re pregnant or breastfeeding
- If you have no or limited sun exposure or the sun has insufficient intensity (i.e. living in the UK, particularly in winter)
- If you cover your skin for cultural reasons or sun protection
- If you’re confined indoors, or just spend most of your time inside
Don’t be fooled thinking you’re safe from vitamin D deficiency in Aus – stats show that 16% of people are deficient over summer, but this level increases to 49% in winter. That’s literally 1 in 2 of us.
If you’re in this high risk group, Osteoporosis Australia recommends a supplement of 1000-2000IU/day (25-50µg). If you’re getting some sun exposure but not at the recommended levels, they suggest a supplement of 600IU/day (15µg).
In the UK, the NHS recommends blanket supplementation over winter of at least 10µg/day.
What about overdosing?
An overdose of vit D can cause too much calcium to get absorbed in your body, which results in calcification (aka hardening) or our arteries and organs. But this only happens if you go bonkers on the supplements for years. It’s basically impossible to overdose in vitamin D from the sun or food and toxicity has been seen in people taking really large amounts of supplements (we’re talking 30,000-50,000IU) over a long period of time. So just be a sensible Sally when it comes to your supplements.
So, there we have it!
Vitamin D has become super important for our overall health and many more of us are becoming deficient.
Taking more will definitely not increase your immunity, but having adequate amounts is really important to prevent a range of illnesses, diseases and health complications.
Big thanks to Dr Joanna McMillan who collaborated this research in her recent webinar through Dietitian Connection.