From hormones to bone health, Vitamin D plays a critical role in many functions within our bodies. And with 30% of New Zealanders not getting enough, now is a good time to learn a bit more about the ‘sunshine vitamin’
So what’s the deal with Vitamin D? Is it really necessary to take vitamin D supplements and what does it actually do in the body?
Why Vitamin D is important
Unlike many other vitamins that we must gain through the food we eat, our bodies actually make Vitamin D with the help of sunlight. Now, the sun doesn’t shoot down rays of vitamin D into our bodies, but we do need the UVB rays from sunlight in order to produce vitamin D in our skin. A type of cholesterol molecule found in skin cells is activated and transformed into pre-vitamin D3 with the help of UVB that hits our skin, it then moves to the liver and kidneys before becoming the active form of vitamin D called 1, 25 – dihydroxy vitamin D3, also called calcitriol (feel free to dazzle significant others with that fun fact!).
Vitamin D then works to keep the calcium and phosphorous in your blood at adequate levels, this means it can cause other molecules called osteoclasts to break down bones to release calcium into the blood stream when it is needed.
Vitamin D also helps the calcium from the food in your gut to be absorbed and transferred into the blood stream. This is important because even if you’re getting a decent amount of calcium in your diet, less of it will be absorbed if you’ve got a vitamin D deficiency. This means more calcium will be released from bones in order to maintain the blood levels of calcium, which can then lead to bone fragility and may lead to osteoporosis later in life. Vitamin D, along with the parathyroid hormone, also helps valuable calcium to be reabsorbed in the kidneys so that you don’t pee it all out!
Vitamin D Deficiency
In the last Adult Nutrition Survey, there was a vitamin D deficiency seen in about 5% of the New Zealand adult population, but there was also an extra 27% of adults that had low Vitamin D levels. That means 1/3 of New Zealanders are not getting enough.
Having low vitamin D is a risk factor for osteoporosis in later life and can cause serious bone deformities in children if not treated. A Vitamin D deficiency in children is predominantly seen as rickets, which causes bowed legs due to leg bones becoming so weak that they bend under the weight of the body. Although most New Zealand children should be getting adequate vitamin D, rickets is a condition that is still occurring in New Zealand.
A vitamin D deficiency in adults can result in osteomalacia which causes bones to soften and can be seen as bowing of the leg bones and bending of the spine. An ongoing vitamin D deficiency also poses a risk for developing osteoporosis, a disease which causes a higher risk of fractures because the bone becomes so fragile due to larger gaps forming in the meshing inside the bone.
People who are at risk of a vitamin D deficiency are the elderly, those that are in hospital or residential care, or have disabilities and aren’t able to get outside into the sunshine. Also, those with darker skin colouring, or very fair skin, those that wear veils, or anyone that is a super sun smart kiwi to the point of no inch of skin ever sees the golden warmth of sunlight, are all at risk of vitamin D deficiency.
There’s also a higher risk of having a deficiency if you live in the South Island and don’t spend a lot of time outside in the middle of the day during Autumn and Winter. Absorption of vitamin D from food can also be reduced in people following an extremely low fat diet which may lead to insufficient vitamin D levels.
There is some evidence that a low vitamin D status has a link with higher rates of illness such as the common cold, and may also have some associations with depression, although more studies are still needed in both of these areas. It’s safe to say though that a day out in the sunshine often has a positive outcome on most peoples’ moods, and may be one tool that depression sufferers may find provides a beneficial effect even for a short time.
How to get enough Vitamin D
Primarily our Vitamin D needs are met by production thanks to sunlight, so if you’re getting adequate sun exposure there is little need to get vitamin D through food or supplements. However, during winter time and for some individuals it will be important to include some vitamin D containing foods such as egg yolks, oily fish like salmon and tuna, and fortified dairy products, plus it doesn’t hurt to consume some of these foods anyway, as they’re also packed with other important nutrients!
There are differing thoughts on exactly how much sunlight you need to produce enough Vitamin D, but aiming for 15 – 30 minutes around midday, a few times a week during winter time is a good start. In summer, earlier or later in the day is better so you don’t get burnt. It’s important to remember though that UVB rays cannot penetrate glass so if you’re sitting in the sunshine inside you aren’t actually producing any vitamin D, it’s best to sit outside. Different people will also need different amounts of sun exposure to produce the same amount of vitamin D – it depends on a lot of different factors such as skin colour, age, if you’re taking medications that make the skin sensitive to sun exposure, where in NZ you live, and the season.
Excess sun exposure won’t cause a vitamin D toxicity, although you may suffer a little sunburn, but toxicity can occur with Vitamin D supplements so it is important that individuals don’t start taking vitamin D supplements without medical advice that they have a low level of Vitamin D or deficiency. Vitamin D is also found in cod liver oil, an old remedy still sold in some pharmacies, so try not to overdose on that delectable treat either!
So what’s the recommendation? I’d say get your lily-white arms and legs out, freak out your neighbour Noleen, and soak up some sunshine this winter!
About Joanna Bunt
Born and raised in small town New Zealand, I qualified as an Art Historian and Interior Designer before leaving for the big city lights of Melbourne. While working for many years in pharmacies I found a new love in the sciences. The role of nutrients in the body fascinated me and I moved home to New Zealand to complete a Graduate Diploma in Human Nutrition through Massey University.
After just recently finishing my studies I now spend my days creating in the kitchen while hunting for the ideal nutrition job, practising my nutrition consulting on willing friends and family, and volunteering with the Garden to Table program! If you would like to contact me regarding career opportunities, writing requests, or have any queries please send an email to: [email protected]
And watch out for my blog that will be popping up in the next couple of months!
Clinical Sports Nutrition (5th ed.) (2015) by Louise Burke and Vicki Deakin.
Nutrition through the Life cycle (5th ed.) (2014) by Judith E. Brown.
Understanding Nutrition Australian and New Zealand Edition (1st ed.) (2011) by Ellie Whitney, Sharon Rady Rolfes, Tim Crowe, David Cameron-Smith, and Adam Walsh.