Parents have been urged to give their children vitamin D supplements after the number of cases of rickets tripled in four years.
Official figures show that 4,638 children admitted to NHS hospitals in 2013/14 were found to be suffering a Vitamin D deficiency, compared with 1,398 cases in 2009/10.
Shortage of vitamin D can cause rickets in children and increase the risk of osteoporosis and cancers in adults.
Experts said some of the problems were likely to be linked to indoor lifestyles, with children spending too much time on computers and gaming consoles during summer, and being left with low stocks of vitamin D when winter arrives.
In Britain, sunlight between November and March is short of ultraviolet B radiation.
The bone-deforming disease - which was rife in the Victorian era - had been virtually wiped out, but has returned and risen five-fold in the past 15 years, figures show.
As well as causing brittle bones, bow legs and other deformities, deficiencies of vitamin D can be fatal, causing a type of heart failure.
A survey of 250 GPs and health visitors commissioned by the Vitamin D Mission, a public health awareness campaign, found almost one third were not aware of Government advice that those aged between six months and five years should take a daily supplement, especially during winter.
Dr Benjamin Jacobs, consultant paediatrician at the Royal National Orthopaedic Hospital, said: "These findings are very worrying as they seem to suggest that parents in the UK are still not properly informed of the major health issues associated with low levels of vitamin D."
Vitamin D can be found in oily fish, egg yolk, red meat and some fortified foods, but sunlight is its major source.
Mum and TV presenter Jenni Falconer, who is supporting the Vitamin D Mission, said: "As a family, we like to spend as much time as possible outdoors and I assumed my little girl would get all the vitamin D she needs from the sun; however, through my work with the Vitamin D Mission I now understand that this isn't the case, especially during the winter months.
"So, I'm going to make a special effort throughout this season to ensure we include more naturally vitamin D-rich foods at home, such as oily fish and eggs as well as vitamin D-enriched cereals and milks, so we're all getting our daily intake of vitamin D and I whole-heartedly encourage other mums and dads to do the same."
Dr Ellie Cannon, celebrity doctor and GP, added: "The average British toddler is only getting 27% of their reference nutrient intake of vitamin D and much more work needs to be done to increase awareness among parents and healthcare professionals.
"Government guidance states that all infants and young children aged 6 months to 5 years should take a daily supplement of vitamin D, and during winter this is particularly important.
"In addition, parents can make a few simple adjustments to their children's diet such as including more naturally-rich and enhanced vitamin D foods."
Nutritionist Juliette Kellow added: "There are only a few naturally occurring food sources of Vitamin D such as oil-rich fish and eggs. It's good news then that many wholegrain cereals are now fortified with Vitamin D.
"A bowl of vitamin D-enriched cereal each morning is a simple, inexpensive and tasty way to introduce more of the sunshine vitamin into our diets and can make an important contribution to our intake of this essential nutrient, especially during the winter months."
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