Ljupka Peev Naturopath, Nutrition, Herbal Medicine for women's health and fertility.

VITAMIN D EXPLAINED

In recent years there has been a huge amount of interest and information on vitamin D. So why is it so important, how much do you need and where can you get it from?

Vitamin D is a fat-soluble vitamin and has many roles and functions in the body. It is thought to function more like a hormone than a vitamin since receptors for vitamin D have been found in many parts of the body including bone, intestine, kidneys, lungs, muscle, skin, the vagina, and heart. It has been found to influence the immune and cardiovascular systems, the control of cell cycles, the brain, mood and more, with many of its actions still unknown. The main role of vitamin D, however, is to maintain blood levels of calcium and support bone health.

Where do we get Vitamin D from?
Who as it at risk of deficiency?
How much do we need?
How much sun exposure do we need?
What if Im deficient?

 

Where do we get Vitamin D from?

Sunlight

Vitamin D is synthesised in the skin by the sun’s ultraviolet-B light. This accounts for 90% of the bioavailable vitamin D. Season, geographic location, time of day, cloud cover, smog, skin colour, sunscreen use and age are among the factors that affect UV radiation exposure & vitamin D synthesis. Adequate sunlight exposure can eliminate the need for dietary intake of vitamin D, but it is estimated that between 5-15 minutes of midday sun exposure every day is required to maintain adequate vitamin D levels in persons living at lower latitudes. Unfortunately, this is also likely to increase skin cancer risk and thus increasing exposure to sunshine is rarely recommended as the sole means to improve vitamin D status.

Dietary sources

There are very few natural food sources of vitamin D and the form found in food is less biologically active, making it virtually impossible to get enough vitamin D from diet alone. Fish liver oils have the highest concentrations of vitamin D, however these are likely to be contaminated with organochlorins, which may negatively impact health. Oily fish are another source but only provide very low amounts of vitamin D.

Food sources of vitamin D (per 100g):

  • Cod liver oil = 8mcg (320 IU)
  • Herring, Atlantic, pickled = 13mcg (520 IU)
  • Butter, dairy blend = 10mcg (400 IU)
  • Fatty fish (salmon, tuna, herring, sardines) = 5-40mcg (200-1,600 IU)
  • Egg yolk, chicken = 2mcg (80 IU)

Other foods may be fortified with vitamin D. In Australia, all edible oil spreads (margarine) must be fortified with vitamin D and some manufacturers of milk, yoghurt and cheese may also fortify their products.

 

Who is at risk of deficiency?

Some groups of people may not get enough sun exposure or their bodies may have trouble using the sunlight to make enough vitamin D to maintain their levels.?People found to be at risk of deficiency include:

  • Everyone living in latitudes south of Sydney
  • Infants and babies of vitamin D deficient mothers (see your practitioner for supplemental advice)
  • The elderly
  • Individuals with limited sun exposure (those who are home-bound or institutionalised)
  • Dark skinned people – melanin (the pigment in skin) reduces UV penetration
  • People who cover most of their skin, such as for religious or cultural reasons
  • People with osteoporosis or osteopaenia
  • Obese individuals
  • Smokers

 

How much do we need?

Recommended daily intake (RDI) for vitamin D for Australia and New Zealand:

  • Infants 0 – 12 months = 5-25mcg (200 – 1,000 IU)
  • From 1 year of age through adulthood (including pregnancy and lactation) = 5-80 mcg (200 – 3,200 IU)
  • 50+ years = 10-80mcg (400-3,200 IU)
  • 70+years = 15-80 (600-3,200 IU)

As you can see from the ranges above, the recommended daily intakes for vitamin D still requires some fine tuning. This is largely because the optimal blood level, which is the only way to reliably assess individual vitamin D status, is also continuously being investigated.

Currently, the recommended blood level of vitamin D (25(OH) D) is above 50nmol/L (or 75nmol/L at some labs). It is important to note that this level is based on the minimal level required to reduce fracture risk in the Australian population and thus the level can vary greatly depending on the outcome that is being assessed. For example, optimal levels for risk reduction in cancer, diabetes, cardiovascular disease, autoimmune disease and others may be as high as 150nmol/L, however this is an area that needs further research. See your practitioner for advice in relation to this.

 

How much sun exposure do we need?

This will depend upon where you live, what time of year it is, how dark your skin is, how much skin you have exposed and your age. The Cancer Council of Australia has provided guidelines for sun exposure in their publication ‘How much sun is enough?’.

For fair-skinned people living in Melbourne, the recommendations are:

  • From May until September – 2 to 3 hours of sunlight over the week, with the face, arms and hands exposed, without sunscreen.
  • From September until May – a few minutes on most days, with the face, arms and hands exposed, before 10am or after 3am (when the UV index is below 3), without sunscreen.

However, there is considerable difference of opinion about what is sensible advice for Melbournians since lower latitude dwellers are unlikely to produce any vitamin D during winter because of the low angle of the sun.

In fact, it has been shown that adequate vitamin D synthesis only occurs between the hours of 10 AM and 3 PM during summer when the sun is overhead, precisely the time when the maximal skin damage will occur. Other experts are thus advising that short periods of sun exposure to the limbs (not face or torso) is the safest way to minimise skin cancer risk and maximise vitamin D synthesis. But really, like a lot of the information about vitamin D, we are still learning what the best advice to give is.

 

What if I’m deficient?

If blood tests reveal a deficiency in vitamin D, you will need to take a supplement to reach and sometimes, to maintain your optimum levels. The amount of vitamin D supplementation required depends on your bloods levels and other factors, such as your level of sun exposure, your age, skin colour, health status. See your practitioner for individualised assessment and treatment.

 

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