From NZ Doctors Speaking Out With Science, 10 March 2023
The Magic of Vitamin D
As we head into autumn, it is worth thinking about vitamin D levels and whether they are optimal for good health during the winter months.
Vitamin D is an important vitamin (it is actually a hormone) that plays a significant role in combatting infections, regulating immune balance and inflammation, and preventing and managing cancer, as well as being important for bone health and mineral absorption.
If you engage with mainstream media, you will have seen increasing articles about the potential infectious threats that are set to befall us – influenza, RSV, measles, whooping cough, meningococcal disease, maybe even bird flu and Marburg virus and, the latest on the block, climate change zombie virus. One way to reduce the chance of poor outcomes from any infections, alarmist or not, is to have optimal levels of Vit D.
Vit D is the ‘sunshine vitamin’ and as sun exposure increases during Sept and Oct body levels start to rise, here in the Southern hemisphere. They will usually be at their highest at the end of summer and then gradually decline during the winter months being at their lowest in July and August.
After the summer we have had (particularly in the North Island), it is likely that many people have not had enough sun exposure to generate optimal vitamin D levels.
In addition to sun exposure, food sources of vitamin D include herring, salmon, tuna and sardines, as well as some beef, liver, eggs and butter. The amount of Vitamin D from animal sources depends on agricultural practices but is never enough on its own. If sun exposure and nutrition are not sufficient, supplements can be taken.
Vitamin D is a fat-soluble vitamin which means it is stored in the body and levels could get too high with excessive supplementation, though this is incredibly rare.
GPs used to be able to test Vitamin D levels for their patients as part of funded blood work, but a number of years ago, the funding for this test was removed. We learnt that low levels occur commonly. A GP can still request it, but there is a charge between $50 and $60 for the test, in addition to the consultation cost.
If you want to know your vitamin D level but don’t need to see your doctor for anything else, you can order a test yourself at https://www.mytests.co.nz/ for a cost of $57.50.
Although the reference ranges are mentioned on this website and suggest that a level of over 50nmol/l is sufficient for bone health, we would suggest a Vit D level between 100 and 150 nmol/l is better with respect to infectious diseases and general prevention..
If you determine your levels are low or likely to be low, there is funded supplementation available from your GP, in the form of 50,000 IU capsules which would commonly be taken once a month. Sometimes they are taken more frequently for a period of time if levels are particularly low. Certainly, for the prevention of infection, evidence is good that daily smaller doses are more effective than occasional high doses.
This is in line with nature, where sun on exposed skin can provide vitamin D on a daily basis. The secret to success is surface area. Exposing more skin for less (than burn) time, but frequently, also helps the body make not just vitamin D from the sun’s UVB radiation, but a powerful protective molecule called nitric oxide too. Also, infrared radiation (the warmth of the sun) penetrates the skin to nourish the blood. No wonder we feel so much better in the sunny outdoors!
Vit D supplements can also be obtained from a health food shop at a lower daily dose, up to 1000IU, the government recommended dose. However, in people who are severely deficient (often unknowingly) this amount won’t even touch the sides. Up to 4000 IU/day is very unlikely to lead to dangerous blood levels.
A note re Measles – vitamin A levels are particularly important for this condition and many third world children with poor outcomes from measles have low levels. Vitamin A as retinol is found in liver, milk, cheese and butter, and as carotenoids is in dark green leafy vegetables (spinach, broccoli) and yellow-orange coloured fruits and vegetables (carrots, capsicum, kumara). It is much safer in pregnancy than previously thought. Vegetable sources cannot cause toxicity.
For more detail about Vitamin D see our previous article here.