What is Vitamin D?
Vitamin D is an essential fat-soluble nutrient found in animal products and fish oils in the form of cholecalciferol (vitamin D3).
What role does Vitamin D play in the body?
Vitamin D is needed for a multitude of body functions and vitamin D receptors (VDRs) are found in most cells and tissues in the body. One of the most well known roles is helping the body absorb and utilise Calcium. If Calcium had to pass through a locked door before the body could actually use it to support healthy bones, vitamin D3 would be the key that unlocked that door. However, maintaining bone health and density is not vitamin D’s only function: it also supports a strong immune system; helps to maintain muscle and joint health, especially in older adults; supports cardiovascular health, and brain function, and influences insulin sensitivity.
How does the body get Vitamin D?
The human body manufactures vitamin D from the cholesterol in skin when it is exposed to Ultra Violet (UV) sunlight. From the skin, vitamin D travels into the circulatory system, which then transports it to the parts of the body that use it, e.g. the bones and muscles. Additional vitamin D can be stored in the muscle and fat tissue. It can occur in several forms, but vitamin D3 (Cholecalciferol) is the form that the body naturally manufactures.
Is sunlight the only source of Vitamin D?
While sunshine is certainly the best natural source of vitamin D, it is not the only one. Some vitamin D3 occurs naturally in foods such as eggs, butter, oily fish (salmon, tuna and sardines), cod liver oil, beef, liver and fortified milk. Some foods are also fortified with vitamin D; and of course, there are vitamin D supplements. However, many people cannot meet their Recommended Daily Intake of vitamin D through diet alone, so most nutritionists recommend sunshine and/or a supplement.
How do I know I’m deficient in Vitamin D?
Vitamin D levels can be measured with a blood test.
The references ranges(1) include:
|Vitamin D serum concentration||Vitamin D status|
|25 nmol/L||Moderate to severe deficiency|
|25-50 nmol/L||Mild deficiency/insufficiency|
|50-100 nmol/L||Optimal range|
|100-150 nmol/L||Associated with adverse effects|
|>250 nmol/L||Vitamin D toxicity|
Who is at risk of a Vitamin D deficiency?
Anyone who is housebound or particularly sensitive to sunlight is unlikely to spend sufficient time exposed to the sun to meet their recommended daily levels of vitamin D. So, for example, people who are ill or in nursing homes, who spend long hours indoors, working in offices, or who work nightshifts and sleep during the day may become low in vitamin D.
Additionally, while melanin (the pigment that determines our skin colouring) helps to protect the skin from the damaging effects of UV light, it also interferes with the body’s ability to manufacture vitamin D; as does clothing that shields skin from sun exposure. This means that people with darker skin, or who cover their arms and faces for cultural reasons, may not be able meet their daily requirements.
Seasonality also plays a large role in determining vitamin D status. For example, cloud cover, air pollution, time of the day, and season, such as during the winter months, can affect vitamin D levels. Distance from the equator is another factor to consider, such as people living in southern regions who spend little time outdoors in the middle of the day between May and August.
How common is Vitamin D deficiency in New Zealand?
Recent data(2) suggests 5 percent of New Zealanders were deficient in Vitamin D (demonstrating blood levels of less than 25 nmol/L) and a further 27 percent demonstrated vitamin D levels between 25 and 50nmol/L.
How do low vitamin D levels affect my health?
Low vitamin D levels are associated with numerous health complaints. Some of these include:
- High blood pressure
- Poor immunity and increased susceptibility to infection
- Autoimmune conditions
- Osteoporosis and increased risk of fracture
- Insulin resistance and Type 2 Diabetes
- Chronic pain
Vitamin D deficiency indicators(3) include:
- Alopecia (falling hair)
- Chronic fatigue syndrome
- Chronic lower back pain
- High blood pressure
- Increased fracture risk in the elderly
How can I maintain my Vitamin D levels?
Vitamin D levels can be maintained with safe, adequate sun exposure. However if you don’t get outdoors often, especially during the winter months, taking a vitamin D supplement may be helpful.
By Eve Storer-Blake BHSc, ND, Dip Med Herb
Nutra-Life Vitamin D 1000IU provides this important vitamin in the same form that our bodies naturally produce. It can help to maintain heart health, strong, dense bones, while also supporting the immune system.
We’d Love Your Feedback
Do you find it hard to get enough exposure to the sun, especially in winter?
If so, have you tried taking a Vitamin D supplement?
(1) Working Group of the Australian and New Zealand Bone and Mineral Society. Vitamin D and adult bone health in Australia and New Zealand: a position statement. MJA 2005;182:281-85.
(2) Ministry of Health NZ, Consensus Statement on Vitamin D and Sun Exposure in New Zealand. March 2012, pg. 4
(3) Braun, L. and Cohen, M. (2010). Herbs & Natural Supplements: An evidence-based guide, 3rd edition, pg. 988