I Just Learned Vitamin D Isn't Really A Vitamin — Here's How It Really Works

The NHS has advised all Brits to consider taking vitamin D supplements in the colder, darker months ahead. 

That’s because our body usually makes its own vitamin D when the sunlight hits our skin, and as anyone who’s stepped outside recently knows, the sun is pretty shy at the minute. 

But speaking to gut health company ZOE’s co-founder Jonathan Wolf on the brand’s podcast, professor of genetic epidemiology at King’s College London Dr Tim Spector and head nutritionist Dr Federica Amati revealed the vitamin isn’t exactly what we think. 

The so-called vitamin “was misnamed a long time ago,” Dr Spector (who also co-founded ZOE) said. 

What’s vitamin D if not a vitamin?

Dr Spector argued that “the definition of a vitamin is something that the body cannot produce itself and you only need minute quantities in order for it to be effective and keep your body going.”

One such example is B vitamins which we can only get from food and which we need to stay alive. 

Vitamin D doesn’t fit this category because “it’s actually [required] in huge amounts compared to the small amounts you need for vitamins already in its natural form, and the body synthesises itself via sunlight.” 

Harvard Health agrees, writing that vitamin D “breaks the rules” of the category because “it’s produced in the human body, it’s absent from all natural foods except fish and egg yolks, and even when it’s obtained from foods, it must be transformed by the body before it can do any good.” 

Vitamin D is made by mixing converted sunlight with various lipids under the skin, Dr Spector added. 

This “is actually more like a pro-hormone or a form of a steroid. So it’s closer to a steroid than it is to a vitamin,” he claimed. 

Dr Amati called it “parahormone D.”

What does vitamin D do?

It’s “crucial for our immune health, primarily,” he added.

But Dr Spector says the amount of vitamin D recommended has “just been pushed up and up and up without really any scientific evidence to say that 28 nanograms is better than 14 nanograms and that there isn’t a universal amount.”

“We did a very large twin study to show that the blood levels you have is not so much dictated by how much you eat or how much you go in the sunshine, but it has a genetic basis,” he shared.

Nonetheless “from a public health perspective, there is little harm in recommending that certain patient groups take vitamin D to help them reach that healthy marker level that we feel would be good for them, basically,” Dr Amati says.