Despite what its name implies, vitamin D is actually a hormone. It has many roles within the body including a part to play in the immune system. Sunlight is one of the best boosters of vitamin D, and during the spring and summer months our children should get enough if they spend short daily stints outside, without sun protection. However, as the dark afternoons draw in, how can we be sure how much vitamin D our children are actually getting?
We all know that calcium is needed for bone growth and strength, but vitamin D is also needed in the metabolic equation to absorb the calcium. This is why vitamin D is often fortified alongside calcium in products such as children’s breakfast cereals and milk. With recent reports of the Victorian disease of Rickets on the increase in children, it might be prudent to keep a closer eye on our children’s intake Only 10% of our vitamin D is usually through our diet – highlighting how problematic this may become during the darker months (Oct-Mar in the UK) when the sun isn’t around to provide us with the other 90%. Wherever you live, an extra dietary boost may be needed during the months where the sun is not high in the sky. Also, those children with darker skin will require more sunlight when they are outside due to the protective nature of darker skin (increased melanin). Dietary sources of vitamin D are fatty fish (salmon, sardine, and mackerel), liver, cheese, egg yolks, butter and in a lesser absorbed form (D2) from mushrooms. Supplementation is usually from cod liver oil or from fortified foods (eg. breakfast cereal, fruit drinks, nut milks, soya milk and margarine).
There are variations of recommended intakes between different countries, with something in the region of 8-25 mcg per day for 0-12 year olds, and a little more for 12-17 year olds, due to their growth phase. Most of this can be met by a daily sunshine exposure of around 15-20 minutes, with top ups coming from dietary sources. Median dietary intakes of vitamin D in children are between 1.9 mcg and 2.4 mcg per day according to a recent Irish study (2); so you can see that during the darker months or if children have their skin almost completely covered, then vitamin D in the blood may become quite low.
It is thought that bouts of asthma are often brought on by a cold or respiratory infection. However, research indicates that when vitamin D supplementation was given in addition to usual steroid inhalers, there was a reduced risk of events triggered by respiratory tract infections. This shows us how vitamin D has an important role to play in reducing inflammatory responses. There is also some speculation as to whether a lack of vitamin D can increase food allergies in children (3). The mechanism occurs as an increase in infections in the gastro-intestinal (GI) tract increases with vitamin D deficiency. As the internal workings of the GI tract becomes further compromised, it brings on an allergic response to certain trigger foods such as dairy, nuts and shellfish. The reason for this is that molecules arising from vitamin D metabolism help to defend the inner gut lining from foreign bodies. Without the correct barrier, the body ‘sees’ certain foods as invaders.
Vitamin D deficiency has been linked to many other disorders including multiple sclerosis, depression, arthritis, heart attacks, seizures, cardiomyopathy, muscle weakness and even cancer.
It is important to note that vitamin D is fat soluble and will build up within the body if taken in excessive amounts for a length of time. However, you cannot get too much vitamin D from exposure to the sun, as the body will only make as much as you need. Obviously, care needs to be taken with reference to long exposure to the sun and the risk of sunburn.
In summary, allowing your child some daily sunshine, where possible, is essential for a natural vitamin D production. Adding into the equation a mix of foods that are high in vitamin D will ensure that ‘all bases are covered’ when the sun isn’t shining.