In Australia and New Zealand, the prevalence of vitamin D deficiency varies, but it’s recognised to be much higher than previously thought, even though we live in a relatively sunny climate. A study of over 11,000 Australians found that 31% of the population were deficient in vitamin D1.
Where can you find vitamin D?
Vitamin D is interchangeably known as a vitamin or hormone and is naturally produced by the body when your skin is exposed to ultraviolet B (UVB) sunlight. The best time for UVB sunlight exposure is between 10am–3pm and should be for a duration of between 5-10 minutes. You can also find small amounts of vitamin D in certain foods, such as cold-water fish, cod liver oil, dark green leafy vegetables, egg yolks and milk, but this may not be enough to maintain good levels of vitamin D.
Vitamin D2 vs D3
There are two types of vitamin D: vitamin D2 and vitamin D3. Vitamin D2 (ergocalciferol) is a synthetic form of vitamin D, whereas vitamin D3 (cholecalciferol) is identical to the vitamin D produced naturally by UVB sunlight exposure. Vitamin D3 is much more effective at raising vitamin D levels in the blood, making it the preferable choice of vitamin D in nutritional supplements.
How much vitamin D is enough?
How much vitamin D you need can be influenced by the starting point of your vitamin D level and your body mass index (BMI) i.e. one size does not fit all. Normal reference ranges for blood levels of vitamin D can vary between pathology laboratories, but it’s generally accepted that blood levels:
- Less than 50nmols/L indicate deficiency
- Between 52-72nmols/L indicate insufficiency
- Between 75-150nmols/L indicate sufficiency
Risk factors for vitamin D deficiency
A significant number of Australians do not receive enough vitamin D and the Australian government has taken steps to correct this by mandating vitamin D fortification in many dairy products. Common risk factors for a vitamin D deficiency include:
- Limited or inadequate exposure to sunlight – excessive sunscreen usage, confinement indoors
- Lifestyle factors – exposure to air pollution, being overweight, excessive alcohol intake
- Dietary deficiency – due to food restrictions such as a low-fat diet, intolerances or allergies
- Ageing – the skins capacity to produce vitamin D is decreased in the elderly
- Dark pigmented skin – the pigment melanin in dark skin can’t absorb as much sunlight
- Some medications
- Issues with absorption in the small intestines
- Women wearing a veil (particularly during pregnancy) and their infants
Vitamin D supplementation helps prevent dietary vitamin D3 deficiency.
The importance of vitamin D for health
Vitamin D plays a crucial role in many areas of your health and is important for maintaining:
- Immune system health
- Bone health - aids the absorption of dietary calcium and a diet deficient in calcium can lead to osteoporosis in later life. Vitamin D is required to support bone mineralisation, density and strength for people in general and for post-menopausal women
- Healthy teeth
- Muscle strength and health
- A healthy pregnancy and supporting healthy foetal development
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1Vitamin D deficiency strikes one-third of Australians. (2012). Retrieved from https://www.deakin.edu.au/research/research-news/articles/vitamin-d-deficiency-strikes-one-third-of-australians