I’m not a big fan of vitamins and other supplements, I believe that a proper diet can supply almost all the micronutrients needed for a healthy life. Fatty cuts of grass fed beef are one of the most nutrient dense food on Earth, liver once a week is a great way to add all the vitamin B12 you need, plus the best possible form of vitamin A (no, carrots don’t have any vitamin A), folic acid and iron.
But when our ancestors moved from the sunny savannah to different latitudes, they started suffering from the lack of vitamin D. Vitamin D is produced by our body through exposure to the sun light: the ultraviolet B component of the light (UVB) is absorbed by the skin, which produces vitamin D3 from 7-dehydrocholesterol (7-DHC), a chemical precursor of vitamin D.
Of course the amount of vitamin D3 produced depends on the intensity of the UVB light, the amount of skin exposed to the sun and the time of exposure: a dark skinned person will require significantly longer exposure than a fair skinned one to produce the same amount.
So, why do we need to add vitamin D3 to our diet? Well, for once because the modern lifestyle keep us indoor most of the time, and the maximum production of vitamin D3 in the skin happens during the central hours of the day, when the sun is high and there is the highest concentration of UVB radiation. So, unless you are in the habit of getting naked in the park at lunchtime every day, and you live not too far from the Equator, your vitamin D production won’t be even close to the amount necessary to stay in good health.
Another factor that strongly limit our UVB exposure is the fact that UVB rays cannot penetrate glass, the sunlight has to hit the skin directly to be ale to start the production of vitamin D3, and there are also some studies that shows how UVA light (that can easily pass through glass) can actually destroy the vitamin D3 present in our skin cells.
The amount of vitamin D3 to take daily is usually 10.000 UI, more or less the amount that you can produce with an hour of exposure to the sun of 80% of your body in Summer during the central hours of the day.
Luckily, vitamin D3 supplements are quite cheap, and the best one are gel capsules with Extra Virgin Olive Oil (stay away from the one with seed oils!).
It’s always good practice to assume vitamin K2 together with vitamin D3 (or if you spend quite a lot of time under the sun): this vitamin is able to direct calcium to where is needed, that is bones and teeth instead of arteries. Vitamin K2 is present in many food, like most of fermented vegetables like sauerkrauts, cheese made with raw milk (I know, you can’t make them here in Australia, but there are several imported from France and Italy on the Australian market) and green leafy vegetables.