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Aveen Bannon - Food Surgery

Friday, 22 May 2009

Are we getting enough Vitamin D in our diets?

According to a recent study undertaken at UCC it was found that Nearly 75 per cent of adults in Ireland have an average daily intake of Vitamin D that is less than half of what is recommended, while 88 per cent of primary schoolchildren don't meet recommended Vitamin D levels.

What is Vitamin D?
Vitamin D is a fat-soluble vitamin that is naturally present in a few foods, added to others, and available as a dietary supplement.

There are two forms of this vitamin; D2 which comes from plants and D3 which is formed by the body when skin is exposed to sunlight. Both D2 and D3 are converted into an active form in the liver and kidney that the body can use.

Why do we need Vitamin D?
Vitamin D plays an essential role in the absorption and use of calcium and phosphorus, so it is imperative for the formation and health of bones, teeth and cartilage. Without sufficient vitamin D bones can become thin, brittle, or misshapen. Prolonged vitamin D deficiency can cause rickets in children and osteomalacia (softening of the bones) in adults. More marginal vitamin D deficiency is likely to be a significant contributing factor to osteoporosis risk. A good dietary intake of calcium and vitamin D can help protect against osteoporosis.

Who is at risk of Vitamin D deficiency?
Elderly people who do not get sufficient skin exposure to sun along with a poor dietary intake, those who cover themselves for religious or cultural reasons, those with malabsorption conditions and those with kidney disease. Also certain medications may interfere with the body's conversion of vitamin D.

What is the recommended daily allowance?
In the UK and Ireland, the recommended daily allowance (RDA) for vitamin D is 0-10µg/ day depending on how much sunlight you obtain. For those aged over 51 years the RDA is 10µg/ day.
The absorption of vitamin D from sunlight can vary at different times of the day and year. Very little if any vitamin D is absorbed through sunlight from October to end of March.
During the summer months we absorb vitamin D from the sun especially between the hours of 11am and 3pm. Therefore extra care needs to be taken with dietary sources of vitamin D in wintertime.

Sunscreen can also reduce vitamin D absorption from the sun as ultraviolet rays are prevented from penetrating the skin.
With both our climate and safe sun protection practises possible factors in affecting our vitamin D status, a good dietary intake, supplements and food fortification are important to help prevent low vitamin D status.

Good dietary sources of vitamin D include;
Oily fish e.g. herring, salmon, tuna, sardines, pilchards and mackerel, fish liver oils and egg yolks are among the best sources. There are also fortified foods available including; dairy produce e.g. supermilk, breakfast cereals and margarines. *See add info for breakdown.

When are supplements necessary?
1. The FSAI now recommend that all babies aged from 0-12months in Ireland are supplemented with vitamin D. It is particularly important for exclusively breast fed babies. We know that breast is the best start for a baby and is recommended for at least the first six months of life. Breast milk is nutritionally complete and contains immunological agents that promote the development of a baby's immune system. However breast milk is a poor source of vitamin D, especially if the mother herself has a low vitamin D status. Supplementation is recommended in;
a. All exclusively breast fed babies (particularly those with dark skin). They should receive 0.3mls of Abidec daily from birth to 12 months. This provides 5µg of vitamin D.
b. Partially breast fed babies should also be supplemented with 0.3 mls of Abidec provided they do not receive more than 500mls of formula per day.2
c. Infant formulas are already fortified with vitamin D therefore babies who are fed infant formula do not require supplementation.
d. All babies no matter how they are fed would benefit from having extra vitamin D as foods containing vitamin D are rarely included in weaning diets. Good sources for babies include Abidec if solely breast fed, infant formula and follow on milks.

2. Those who are confined to indoors may benefit from a vitamin D supplement.
3. Elderly adults may benefit from supplements for two reasons. One is that negligible absorption of vitamin D occurs between October and the end of March but the second factor is that skin syntheses of vitamin D can decrease with age. A daily intake of 10 µg is recommended for adults aged 51-70 years. However recent Irish research has shown that 89% of 51-64 year olds do not achieve the 10µg/day recommendation, with mean daily intakes (MDI) of vitamin D from food sources being 4.01 µg in men and 3.39 µg in women.3 Results like this show us that we need to concentrate on good dietary sources in the diet and supplementation should be promoted amongst our older population.

References;
1. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom, 1996
2. Vitamin D - new recommendations from the food safety authority o f Ireland, www.fsai.ie
3. UCC vitamin D research group; www.ucc.ie/en/vitamin

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