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Vitamin D – the most important hormone of all?

Feeling the warmth of the sun on your skin after a long winter is amazing isn’t it? I think it’s your body drinking in the Vitamin D that it’s been lacking for such a long time.

We know Vitamin D is the ‘sunshine vitamin’ but did you know, it is actually a hormone? And it’s absolutely vital to keep us in optimal health.

Here in Europe we are coming out of our winter hibernation, and seeing some long-awaited sunshine. Not just important for boosting our mood (how many more smiles do you see when the sun’s out?), but incredibly important for topping up our Vitamin D stores that have been depleted over the winter.

Are you deficient? Probably!

According to the National Diet and Nutrition Survey, 90% of the general population in the United Kingdom have insufficient blood levels of vitamin D, and 5%-20% of the population are in a state of severe deficiency.

Where do we get it from?
The main source of Vitamin D is from direct sunlight, so unless you’re holidaying in the Caribbean every few weeks during the winter months, you are likely going to be deficient! According to UK Government guidelines, we only get enough sunlight to make Vitamin D between mid May and September. You can get small amounts from animal foods, such as egg yolks, meat, oily fish and dairy, but it’s not enough to keep your levels in the optimal range.

You can get a good 10,000 IU of Vitamin D from exposure to direct sunlight in 10- 20 minutes (without suncream!). The skin absorbs the UVB radiation from the sun, converts it to Vitamin D3, then the liver and kidneys transform it again into the active form (1,25(OH)2D.) to do it’s work.

Why is Vitamin D so important?

Nearly every cell in your body has a Vitamin D receptor, and more and more evidence is now confirming that it’s role in the body is much wider than just protecting your bones.

  • Immune booster – it helps to fight infection. Maybe that’s why we get more colds and flu in the winter time when there’s no sunlight?
  • Auto-immune protection – many conditions such as MS, Crohn’s, Rheumatoid Arthritis, Hashimoto’s and other auto-immune conditions have been linked to Vitamin D deficiency
  • Cancer protection – more and more evidence now points to the links between vitamin D deficiency and certain cancers, including breast, prostate and colon cancer. One study claims rates of these cancers would be cut by 50% if we got adequate amounts!
  • Bone and muscle health – it regulates calcium levels and the activity of bone building cells (severe deficiency we know causes rickets)
  • Brain health – it plays a crucial role in neurological health, mood and cognitive function
  • Heart health – it prevents calcium build up in the arteries, helps to normalise blood pressure and reduce inflammation
  • Skin – it helps to prevent excess cell proliferation (eg psoriasis, eczema)
  • Blood sugar balance and insulin control – it helps to regulate blood sugar and prevent insulin resistance

What can affect your levels of Vitamin D?

  • Lack of exposure to sunshine – whether that is lack of actual sunshine all year round, covering up or avoiding the sun (or wearing sunblock)
  • Darker skin – the darker your skin the more sun you need to be exposed to
  • Kidney or liver disease – as Vitamin D is converted in the liver and kidneys, any issues here can lower your levels
  • Pregnancy – you need extra amounts in pregnancy for building baby’s bones
  • Stresscortisol is a steroid hormone made from cholesterol. If the body is stressed, cortisol will take priority over the synthesis of Vitamin D
  • Obesity – can reduce the biological activity of Vitamin D
  • Genetics – certain gene mutations can cause lower levels of Vitamin D

If any of these affect you, then you will more than likely need to add a Vitamin D3 supplement to your daily routine.

How do we know how much we need?

You need to get your levels tested to properly determine how much you need to supplement;

Reference range UK;

Status Blood level
Deficient < 25 nmol
Insufficient 25-50 nmol
Adequate 50-75 nmol
Optimal >75 nmol


Like anything, toxicity is possible if you take too much for a long period of time, but experts say that occurrences are very rare and many high dose supplement protocols have been undertaken with no adverse effects.

The current daily recommendation for vitamin D is 200iu. Recent medical research indicates that human daily requirements of vitamin D may be up to 10x more than this. If you consider that the skin will naturally produce approximately 10,000iu vitamin D in response to 20-30 minutes summer sun exposure, you can easily see how 200iu might be considered too low!

If you have had a blood test and know your current levels, Grassroots Health has a fantastic calculator that you can use to determine how much you need to take. You put in your weight, current levels and desired levels and it calculates how many IU you need to get there. You will need to convert your nmol reading to their ng reading (UK to US) – they have a handy serum level converter on the home page too.

Vitamin D doesn’t work alone!

Vitamin D has to have help from certain co-factors to work properly in the body. These include Magnesium, Vitamin K2, Vitamin A, Boron, Zinc. So if you start supplementing with vitamin D, make sure you are also getting these co-factors too or you risk causing more imbalances.

I recommend a good quality multivitamin, plus a Vitamin D complete with all your fat soluble vitamins (A, E, K) to ensure you get the full spectrum. (If you order anything from the Natural Dispensary, use code NJW010 for a 10% discount). But please check with your Doctor or health practitioner before starting any new supplements.


  • Get sun exposure, without sunscreen, for 20 minutes whenever possible (without burning)
  • Eat oily fish, egg yolks, organ meats to top up your levels during the winter
  • Get tested
  • Supplement with D3 during the winter months
  • Supplement with D3 co-factor vitamins and minerals

If you want to read more about Vitamin D, these are some of my favourite blogs.

Nicki WilliamsVitamin D – the most important hormone of all?

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