By Ania Lichtarowicz
BBC Science Reporter
Modern life has been blamed for a resurgence in cases of the crippling bone disease rickets.
Rickets weakens the bones
Doctors writing in The Lancet medical journal warn that rickets - which many see as a disease of the past - is still a global health problem.
They say that concern about the health effects of exposure to sunlight, and increasing levels of pollution have played a role.
In addition, the promotion of exclusive breastfeeding for long periods without vitamin D supplementation could be a factor.
And they say that one way to combat the problem would be to give all pregnant women and children up to puberty vitamin D supplements.
Rickets is usually caused by a lack of vitamin D which stops the body from absorbing calcium needed to make strong, healthy bones.
We make vitamin D in our skin from sunlight - just five to ten minutes exposure can be enough to produce a day's worth of the nutrient.
But fear of skin cancer means many parents make children cover up in the sun.
And it is estimated sunscreen blocks about 90% of ultraviolet light - leaving our bodies unable to make enough vitamin D.
Professor Nick Bishop, from the University of Sheffield was one of the doctors behind the work.
He said: "It's coming back largely because of social factors and concerns about sun exposure - which obviously are entirely appropriate and justified.
"Most parents these days will put cream on their children even before they go outside or put a hat on them and the children don't make vitamin D in the skin."
The same is true in cultures where people cover themselves completely for social or religious reasons.
The researchers also believe that increasing levels of atmospheric pollution are responsible for an increase in cases of rickets, particularly in India and China.
Pollutants block the ultraviolet component of sunlight from reaching ground level.
The problem is not yet at epidemic proportions, but the numbers are increasing significantly each year.
Professor Bishop says the disease can be seen everywhere.
"If we look at countries where people cover their skin with cloth because of social or religious reasons - say in the Middle East, there are lots of mums there with the adult form of rickets and children with rickets as well.
"They don't get enough vitamin D form the sunlight and they don't get any in their diet either."
The researchers argue that giving pregnant women vitamin D supplements would be an effective way to combat the problem.
They also emphasise that a short period of exposure to sunlight every day is a good thing - and could stop rickets resurfacing on a major scale.