Also known as the ‘sunshine vitamin’, Vitamin D is a fat soluble vitamin that people often neglect. In fact 1/5 of the UK and nearly 1/2 of the US are considered to be deficient.
What is Vitamin D?
Vitamin D is a steroid hormone produced from cholesterol, activated when your skin is exposed to the sun. In fact (if you live somewhere sunny) your body can make up to 90% of the vitamin D that you need, so the latter 10% comes from foods.
That said if you live somewhere, perhaps like the UK, or if you prefer to stay covered up in the sun- you could find yourself short. Particularly in the winter months.
There are 2 kinds of Vitamin D-
Vit D2- (ergocalciferol)- found in some plants and mushrooms.
Vit D3- (cholecalciferol)- found in animal foods like fatty fish and egg yolks.
D3 is the kind that we make endogenously (within our body) upon exposure to sunlight and for this reason this is the most highly recommended to supplement as we already produce it.
Benefits and Requirements:
The main point with Vitamin D is to not be deficient, as this poses more problems.
The benefits of Vitamin D are slightly hit and miss, with research studies often finding contrasting results. It was believed that Vit D played a role in strengthening bones, and whilst it’s been found to aid absorption of calcium and phosphorous from your gut. Unless you have low bones mass, have osteoporosis or are in fact deficient in the vitamin itself, Vitamin D didn’t find a clinically meaningful decrease in fracture risk.
That said- it has been shown to be an aid to immune health, particularly in the defence against upper respiratory tract infections. As well as some research into musculoskeletal function, reducing stress fractures and regulating blood sugar in those with type 2 diabetes.
Supplementation.
The RDA for Vit D is 600-800 IU per day.
Being a fat soluble vitamin, it is stored in the body, this means you could take a vitamin with 10,000 IU once every 7-10 days or you could take a lower dose daily.
Try taking your vitamin with food, preferably a fatty meal or even a slice of avocado to increase absorption.
In the UK, during summer months between 11am-3pm, this is when the most effective synthesis from sunlight occurs. However, during the winter we find ourselves needing to take a supplement.
People with darker skin contain more melanin in their skin, which acts as a natural sunscreen- this means that they need up to 5-10 times more time in the sun to gain the same results, and can find themselves at a higher risk of deficiency. Aswell as vegetarians and vegans, who aren’t able to get the same amount from food sources as an omnivore.
D3 seems to be almost twice as effective at increasing blood levels of vitamin D compared to D2.
Some sources include:
- Cod Liver oil, providing 227% of the RDA
- Salmon, providing 75%
- Tuna, providing 26%
- Egg yolk, providing 7%
The bottom line is, if you live in the UK and/or spend a lot of time indoors it’s recommended you find yourself a D3 supplement.