Sun glorious sun...do I have enough vitamin D?
I hope you had a wonderful Easter and were able to get out and enjoy some amazing sunshine to rejuvenate and boost your immune system.
As we head into autumn and cooler weather, sunshine and vitamin D become evermore important to keep our immune systems in tip-top shape. Vitamin D helps optimise our white cell production and help our bodies fight infection from invasive organisms.
A good place to start is getting your vitamin D level checked with a blood test - ask your GP. The "normal" range in Australia is 50 - 150nmol/L (this may vary slightly from laboratory to laboratory). If you are reading about vitamin D in other countries you may see the unit ng/mL. 1ng/mL = 2.5nmol/L if you want to convert.
As you can see it's a massive range and there is still debate over what the most beneficial level within this range is.
Get tested at the same time of year, at the same laboratory and note if you are taking vitamin D supplementation and how much at the time of testing. Getting tested at the same laboratory is crucial as different laboratories use different testing methods which can make quite a big difference in results. If you want to know what your naturally lowest level is - test at the end of winter when you've had the least exposure to UVB rays. And vice versa, if you want to know how high your vitamin D level gets naturally with sun exposure - test at the end of summer i.e. now.
Do I need supplementation?
Here are some general guidelines for supplementation but these are not intended to substitute for individual advice from a healthcare practitioner with knowledge of your medical history.
If you were to get a blood test now and your level was:
< 50 nmol/L you may need approximately 3000IU vitamin D per day
50-75 nmol/L - 2000IU/day
75-100 nmol/L - 1000IU/day
> 100 nmol/L - unlikely that any supplementation is needed
Take vitamin D with vitamin K as the latest research is showing they work synergistically.
Can I get vitamin D from foods?
Oily fish is a great source of vitamin D. This includes fresh and tinned salmon, fresh tuna, sardines, herrings and mackerel.
Cod liver oil is also a really good source of vitamin D.
Egg yolk and the offal meats kidney and liver contain some vitamin D but only 25 - 50 IU compared to 400 - 500 IU for oily fish and cod liver oil.
How much sun exposure do I need to get a good daily dose of vitamin D?
Firstly determine when you have access to UVB rays from the sun. For the southern hemisphere, if you live more than 37 degrees south of the equator, you will likely get no UVB ray exposure in autumn and winter. This is the opposite for the northern hemisphere - more than 37 degrees north of the equator.
Here are the latitudes of the main Aussie cities:
Here in Adelaide we are borderline so during autumn and winter our bodies are mostly relying on the stores of vitamin D that have built up over the spring and summer. Vitamin D is fat soluble so it can store in the body as opposed to vitamin C or Bs which are water soluble. If you live in the tropics or sub-tropics you may have access to UVB rays all year round in which case you may be able to rely on sun exposure to keep a good blood level of vitamin D.
When you do have access to UVB rays you want to expose your arms and legs to the sunshine for at least half the time it takes for them to start to go pink or feel really warm but not burn. This will vary from one person to the next. For the translucently pale among us (myself included!) this doesn't take very long at all but the darker your skin the longer it will take. This will also vary depending on the time of day and the season - be careful at midday in summer! This exposure needs to be with no sunscreen on then if you need to be out in the sun for longer use a sunscreen or cover up with light clothing.
The other important aspects for optimal vitamin D are your liver and kidney health. After sun exposure or taking supplements, the vitamin D has to be converted in the liver and the kidneys to become its active form. So...you know the score - more leafy greens, more cruciferous veggies (cabbage family), more water, less alcohol, less coffee (I can hear hubby groaning from here!) The usual suspects :)
Happy sunning yourselves!