Vitamin D: The sun and seafood hormone

Vitamin D is essential for maintaining calcium concentrations in your blood. It does this by enhancing the small intestines ability to absorb dietary calcium. And in relation to calcium, it is therefore very important for bone health.

Further to this, Vitamin D is likely involved in maintaining the immune system, as well as plays a role in both skin health and muscle strength.

When you do not consume enough calcium from your diet, the active form of vitamin D (calcitriol) works with parathyroid hormone to turn on cells (osteoclasts) that mobilise calcium stores from your bones.

Overtime, if you continuously do not get enough calcium and/or Vitamin D, your bones will weaken.

Vitamin D deficiency...

Vitamin D deficiency results in inadequate mineralisation (bone formation), as well as demineralistation (bone loss) of the skeleton. This can lead to bowed legs and knocked knees in children, formally labelled as rickets. In adults, vitamin D deficiency can lead to osteoporosis (weak bones) and increased risk of fractures.

Theres more than one type of Vitamin D...

Vitamin D comes in two forms:

(1) Vitamin D3 (Cholecalciferol), which is produced by the action of sunlight on your skin, and

(2) Vitamin D2 (Ergocalciferol), which is found in a limited range of foods.

Diet alone is pretty much impossible to obtain your Vitamin D needs, but if sunlight exposure is adequate, all your vitamin D needs can likely be met.

Foods sources of Vitamin D

As mentioned above, Vitamin D is found in very few foods, including some fortified foods (e.g. margarines, soy milks), eggs, fatty fish such as salmon, herring and mackerel, and mushrooms exposed to ultraviolet light. But to mention it again, it is pretty much impossible to obtain your Vitamin D needs from foods alone.

Getting enough Vitamin D

The sun...

Ultraviolet radiation (UV) from the sun is the best natural source of vitamin D. In terms of safe sun exposure, this is dependent on the time of year, where you live, as well as your natural skin type. To help your body make enough vitamin D, get active outdoors every day and apply appropriate sun safety recommendations.

Greater sun exposure time is required for those with darker skin and for those living in more southerly latitudes (i.e. further away from equator).


If adequate sun exposure is not possible, a supplement is advisable. To prevent vitamin D deficiency in people who do not achieve adequate sun exposure, the following is recommended:

  • < 70 years old = At least 600 IU of Vitamin D per day

  • > 70 years old = A least 800 IU of Vitamin D per day

  • Vitamin D deficiency / high risk deficiency = higher doses (e.g. 1000 – 2000 IU per day).

Speak to your Dietitian, Doctor or Pharmacist for advise regarding Vitamin D supplements.