Vitamin D: How do you know if you are getting enough?

Vitamin D, the sunshine vitamin, is famous for its role in helping our bodies absorb calcium to keep our bones strong.

Despite the abundance of sun in Australia, more than 1 in every 4 Australian adults are deficient in vitamin D which can lead to osteoporosis, bone and joint pain. Older people who don’t have enough vitamin D are more likely to fall and fracture their bones.

To keep our bones healthy and strong adults need 5 - 15 µg of vitamin D a day, increasing as we get older. Australians get about 90% of their vitamin D requirements from the sunlight on their skin, and 10% from the food they eat. So, what happens when we spend so much time indoors?

Can we get enough vitamin D in winter?

Spending a lot of time indoors or being housebound is a risk factor for low vitamin D.

We see this happen naturally with changes of seasons. The Australian data on vitamin D levels shows that in summer 14% of us are low in vitamin D, while in winter this increases to 36%, and even higher among Australian women (more than 50%).

Spending time outside really is important. As well as being good for our mental wellbeing, it helps restore levels of vitamin D and whether it’s a cuppa on the balcony, some gardening in the backyard, chatting to a neighbour, walking to the shops or exercising outside – any time in the sunshine counts.

How much time in the sun do we need to get enough vitamin D?

It’s tough to give an exact amount of time as this will depend on a range of factors, including where you live, what time of day it is, the colour of your skin and how much skin is exposed.

A review of research commissioned by the Australian and New Zealand Bone and Mineral Society and Osteoporosis Australia recommends: “for people with moderately fair skin, adequate vitamin D levels are likely to be maintained in summer by a walk outside with arms exposed for 6-7 minutes, mid-morning or mid-afternoon, on most days. In winter the task is more difficult but, depending on latitude, walking outside at lunchtime for 7-40 minutes, with as much bare skin exposed as feasible."

The further away from the equator you live, the more time outside you’ll need. So, in winter it’s 29 minutes for those in Hobart, compared to 7 minutes for those in Cairns.

If the UV index is 3 or above sun protection is recommended while outside, for most people.

Can I get vitamin D from food?

You can get vitamin D in small amounts from foods including eggs, oily fish, UV-irradiated mushrooms. What’s that you ask? Like our skin, mushrooms convert the sunlight they absorb into vitamin D, so placing mushrooms in the sun can increase the amount of vitamin D they contain. Eating a 100g serve of mushrooms that has been left in the sun for an hour, will provide your daily dietary vitamin D needs.

There are also several foods that have been fortified with vitamin D including soy milks, almond milks and some margarines and milk.

In cases of vitamin D deficiency, health professionals may also prescribe vitamin D supplements.

What happens if I don’t get enough vitamin D?

Low levels of vitamin D can increase your risk of bone and joint pain and the chance of fractures and broken bones, especially if you are over 50. It’s also a risk factor for osteoporosis.

Osteoporosis makes bones brittle and occurs when your bones lose minerals, like calcium, quicker than our body can replace them. Vitamin D plays an important role in helping our body absorb calcium.

There are also several diseases that have been linked to low vitamin D levels including cardiovascular disease, severe asthma and cancer. While moderate or severe vitamin D deficiencies in infants and children can lead to soft bones or rickets.

If you have any questions or concerns about your vitamin D levels please speak to your GP or a dietitian.