We all know that vitamin D is good for us but just how much sunshine do we need to get enough?
How much vitamin D do you need?
Do you know what your vitamin D level is? For most people it’s lower than we expect. After all Australia is known for its sunshine, and sun is necessary for our body to make the vitamin. But the research tells a different story. Surprisingly most Australians, when are tested, are actually deficient in this nutrient.
However the tests, or more specifically the reference ranges used, remain controversial. Pathology labs in Melbourne use at least three different ranges, leading to the bottom end of “normal” varying from 50 – 75 ng/ml. Most researchers in this field believe the higher figure to be more accurate for the prevention of many diseases.
The variation partly is connected with increasing evidence that vitamin D plays a greater role in our health than just keeping our bones strong. A deficiency in vitamin D is linked to various cancers, autoimmune conditions, cardiovascular and metabolic diseases, neurological and even mental health problems. Being deficient can also make you feel unhappy, interfere with your sleep and even make you more likely to get the flu.
Ultra violet light (UV) from the sun is a plentiful source of vitamin D, thanks to the way our body synthesises the vitamin in the skin, but a number of factors stop us from getting enough. Our skin colour, the latitude of where we live, use of sun block, clothing and time of day we spend in the sun, all play a role in how much vitamin D we can make, and need.
During a Melbourne winter for example, we need an estimated 32 to 52 minutes of sun, with our arms and legs exposed to generate our daily requirements. Not an easy feat in a season dominated by grey skies, cold weather and rain. Considering many people commute in the dark or low light at this time of year, even with sufficient skin exposed, you’re unlikely to get enough UV at lunchtime to meet your daily requirements.
Keep in mind that the exposure guide (in the Medical Journal of Australia) is based on those with an Anglo/Celtic skin type – dark skinned people need significantly more time in the sun. It’s not hard to see why so many people are deficient, let alone those who are housebound, do shift work or dress modestly. Other factors, such as obesity and digestive conditions can also interfere with the way vitamin D is absorbed or utilized.
Gill’s recommended vitamin D dosage
There are a few foods that contain vitamin D, such as liver, some types of fish and eggs, as well as a few fortified dairy products and spreads. However accurate information regarding the actual vitamin D content of Australian foods is not available according to a recent Medical Journal of Australia position statement.
As there is no consensus on what levels of vitamin D are “normal”, the supplement dose also varies. Below is my current recommended dosage range based on blood test results. If you don’t know your level, it might be a good idea to see your GP for an annual check-up and request the test. Don’t forget to get a copy of your results to share with your naturopath.
|mol/L serum 25-hydroxy vitamin D||Dose D3/Day|
Take the recommended dose for 9 – 12 weeks.
If you’re tested at the end of summer and find that you’re only in the bottom of normal range (<80 ng/mol), it’s still a good idea to supplement during the winter months. For example, take a dose of 1,000 iu most days from the end of daylight saving time to the beginning of summer.
At the other end of the scale – for those who are severely deficient there is increasing evidence to use of doses of 5,000 iu and above, per day. Many doctors in New Zealand prescribe a monthly dose of 50,000 iu, although this is not yet common practice in Australia.
Can you have too much vitamin D?
Accounts of vitamin D toxicity are rare, according to the Vitamin D Council.
The Vic Health websites states overdose symptoms may include headache, weakness, drowsiness, dry mouth, nausea, vomiting, constipation, muscle or bone pain, metallic taste in the mouth, weight loss, itchy skin, changes in heart rate, loss of interest in sex, confusion, unusual thoughts or behaviour, severe pain in your upper stomach spreading to your back, or fainting. If you develop any of these symptoms, stop taking supplemental vitamin D immediately and see your doctor.
But keep in mind doctors in some countries prescribe up to 50,000 iu of vitamin D3 as a single dose with little or no adverse reactions. One recent study even used a 300,000 iu single dose to treat painful periods.
Read more about vitamin D, including other causes of vitamin D deficiency.