D in the Diet

In Australia, the major dietary sources of vitamin D are found in margarine (50%), canned fish such as herrings and salmon (16%) and eggs (10%). Other sources include butter, cheddar cheese and lean meat. Milk is low in vitamin D unless it is fortified.

Mushrooms that grow in the wild are naturally high in vitamin D. Cultivated mushrooms that are exposed to light also have vitamin D. In fact, just a 100 gram serve of light-exposed mushrooms provides the daily needs of vitamin D.

Approximate Vitamin D in Foods

Food Vitamin D mcg
Fruit, vegetables 0
Egg, 1 whole (50g) 0.5
Margarine 2 teaspoon 1.0
Beef, 100g 1.0
Salmon, 100g 1.0
Tuna, 100g 2.0
Milk, vitamin D fortified, 200 mL 1.0 - 4.0
Mushrooms, retail, 100g 0 - 0.5
Mushrooms, light exposed, 100g 20.0+


How much D do we need?

The older we get, the more vitamin D we need. Despite exposure to sunlight, aging causes our skin to produce less vitamin D and our kidneys produce less of the active form of vitamin D.

The table below outlines the recommended vitamin D daily needs as stated in the Nutrient Reference Values for Australia and New Zealand (NHMRC 2005) and from the United States Institute of Medicine (IOM 2010).

Age Adequate Intake (ANZ) RDA (US)
1-18 years 5 mcg (200 IU) 15 mcg (600 IU)
19-50 years 5 mcg (200 IU) 15 mcg (600 IU)
50-70 years 10 mcg (400 IU) 15 mcg (600 IU)
70+ years 15 mcg (600 IU) 20 mcg (800 IU)

Note: Vitamin D is often expressed in International Units for supplements. One microgram is equal to 40 IU; 1000 IU vitamin D tablet = 25 mcg.

The latest research findings for vitamin D saw the United States Institute of Medicine recently increase the recommended requirements for vitamin D. In Australia, the new Nutrient Reference Values for Australia and New Zealand will not be released until 2013. It is expected this update may include an increase in the recommended needs for vitamin D.

With the weight of research now highlighting the importance of maintaining adequate levels of vitamin D, dietary sources are likely to continue to grow in value. Mushrooms are a practical and tasty way to obtain vitamin D, in amounts that provide the recommended Adequate Intake levels of vitamin D.

Insufficiency

In recent years, vitamin D has become of great interest to health researchers and medical authorities around the world. Research has linked vitamin D to a rapidly increasing number of benefits beyond healthy bones and the prevention of rickets and osteoporosis. These include a decreased risk of multiple sclerosis, diabetes, rheumatoid arthritis, high blood pressure, influenza, heart disease, bowel cancer, breast cancer, prostate cancer, ovarian cancer and depression. Researchers have found there is a link between vitamin D deficiency and the risk of falls and bone fragility fractures.

Are you at risk?

The World Health Organisation identifies infants, adolescents, the elderly, and pregnant and lactating women as the main risk populations for vitamin D deficiency.

Infants have relatively large vitamin D needs due to their high rate of skeletal growth. This can be further compounded by restricted sunlight exposure. Skeletal growth is also rapid during puberty, making adolescents more susceptible to vitamin D deficiency.

As we age, it becomes more difficult to obtain our vitamin D requirements from the sun. The technical explanation is that there is a reduced amount of skin conversion to cholecalciferol; reduced conversion to calcitriol in the kidneys and a lesser response by target tissues such as bone. The simple explanation is that we need further help as we age to obtain our required levels of vitamin D.

The difficulties are further compounded if people have less sunlight exposure due to illness or reduced mobility. As human milk is a poor source of vitamin D, often due to mother’s low exposure to sunlight, rickets can occur in breast-fed infants deprived of sunlight exposure.

People who risk having low vitamin D are those living far from the equator, those with dark skin (UV light cannot reach the appropriate layer of skin), those who completely cover the skin for medical, cultural, environmental, social or religious reasons and those who liberally use sunscreens which inhibit the skin production of vitamin D (WHO 2004).

How do Australians rate with vitamin D?

It is a mistake to think that most people in Australia get enough vitamin D each day from the sun. Vitamin D insufficiency is prevalent in Australia. Many people avoid the sun during the day due to work commitments or fear of skin cancer. Published research shows that vitamin D insufficiency (plasma < 50 nmol/L) is found in:

  1. 28% of Sydney office workers in summer (Fayet 2011)
  2. 30% of healthy women in Geelong (Pasco 2001)
  3. 41% of people in south-east Queensland (van der Mei 2007)
  4. 42% of Sydney office workers in the winter (Fayet 2011)
  5. 58% of aged care residents in Melbourne (Woods 2009)
  6. 67% of Tasmanian women (van der Mei 2007)
  7. 70% of people living in hostels (position statement MJA 2005)
  8. 74% of general inpatients in a Melbourne hospital (Chatfield 2007)
  9. 80% of women Royal Women’s Hospital Melbourne (Erbas 2008)
  10. 83% of dermatologists in the winter (Czarnecki 2009)
  11. 87% of African refugees in Sydney (Benitez-Aguirre 2009)

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