Sunshine delivers the vitamin D hit humans need - Stuff.co.nz

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Sunshine plays important biological roles for humans.

OPINION: Auckland-born pop sensation Lorde is once again climbing to the top of music charts around the world, this time with the album and song Solar Power, odes to the sun.

The rest of us love the sun as well. From my vantage point overlooking Wellington’s Oriental Bay, I’ve watched sunbathers soaking it up in a socially distanced manner as they’ve enjoyed the slightly looser restrictions of level 3 lockdown. Come summer, Covid-free status and weather permitting, you won’t be able to see the sand for the beachgoers.

The sun literally keeps us alive by preventing us from freezing to death and allowing plants to grow. But it does something incredible to our biology as well. When exposed to the sun we absorb, through our skin, the ultraviolet B radiation it emits.

That energy triggers the creation of chemicals in our skin, which are then metabolised in our bodies by the liver and kidneys to create vitamin D, the only vitamin that is produced in the body.

Vitamin D increases the intestinal absorption of calcium from the food that we eat. That’s the key to good muscle and bone health. We need a modest amount of exposure to direct sunlight to get all the vitamin D that we need.

Despite that, prescriptions for vitamin D supplements in New Zealand jumped 14-fold between 2003 and 2019 to 1 million prescriptions a year, according to a study published in the latest New Zealand Medical Journal.

Vitamin D supplements have an interesting origin. They are typically made from a fatty substance that is excreted by sheep to keep their wool coat in good condition. It is used to make lanolin but is the precursor to vitamin D3, which when exposed to ultraviolet radiation mimics the reaction in our skin that produces vitamin D. A vegan form of vitamin D is extracted from plants such as algae.

Have all of those cheap vitamin D pills we’ve been popping done us any good? Probably not. Physically, serious vitamin D deficiency manifests in two ways – rickets, a skeletal disorder that impedes bone development in children, and osteomalacia, a condition where bones can become soft and weak.

The scientists analysed annual hospital admissions and found that despite the major increase in vitamin D prescriptions over recent years, cases of rickets and osteomalacia remain steady at between 10 and 20 cases each year. In addition, measuring of vitamin D levels since 2009 found most people weren’t low in the nutrient.

ROBERT KITCHIN/Stuff

Stuff science columnist Peter Griffin.

They pin the increase in supplement use on outdated advice that suggested vitamin D was useful in helping prevent falls and, in conjunction with calcium supplements, reduced bone fractures.

Clinical trials have since found that vitamin D supplements on their own don’t improve bone density. The advice on taking calcium supplements to prevent fractures has also changed. It is no longer recommended, the researchers write, “because the risks outweigh the benefits”.

So get some sun, it will do you a world of good. Just don’t get sunburn.

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