Why the sun shines on summer babies

Ultraviolet rays make pregnant women have taller offspring with stronger bones

Women who are pregnant during the summer have taller, stronger-boned babies because they benefit from the sun's vitamin-boosting rays, a study suggested yesterday.

Children born in late summer or early autumn are about 5mm taller and have thicker bones than those born in winter or spring, an 18-year research project found.

Women lucky enough to be blooming in hotter months should get enough sun to boost their vitamin D levels just by walking around outside or even sunbathing. But those pregnant over winter should consider taking vitamin supplements, researchers at Bristol University recommended.

Anyone thinking of trying to short-cut the process by sitting on a sunbed in the final weeks of pregnancy would do themselves no good. Sunbeds emit mainly UVA light, whereas natural UVB rays from the sun trigger vitamin D production. Sunbed users also face well-publicised risks. Sally Watson, a spokeswoman for the study, said: "Perhaps people should not be quite so terrified of the sun. There has been a lot of panic about skin cancer but people do not need to panic about the odd few minutes of exposure. A little controlled English sun is better than none."

The Bristol team assessed the mothers of 7,000 children and calculated their likely exposure to sunshine during the last three months of pregnancy. At the age of 10, their offspring were measured and given X-ray scans to determine their bone density. Compared with the children born in winter months, those whose mothers had the highest sun exposure were, on average, 5mm taller and had 12.75 sq cm more bone area because their bones were thicker.

Taller people tend to have wider bones but these children had increased bone width "over and above" that accounted for by their extra height, the team discovered. This increase in bone mass could be attributed to higher vitamin D levels, proving that vitamin D is important for bone-building even in the womb, the researchers said.

Vitamin D, which works with calcium to build bones, is generated by sunlight on skin and for most people, this is their main source of the chemical. Vitamin D levels in the blood of 350 mothers in the 37th week of pregnancy were also measured, and were found to closely mirror their sun exposure levels.

One of the researchers, Professor Jon Tobias, said: "Wider bones are thought to be stronger and less prone to breaking as a result of osteoporosis in later life, so anything that affects early bone development is significant. Pregnant women might consider talking to their doctor about taking vitamin D supplements, particularly if their babies are due between November and May, when sunlight levels are low."

The findings are the latest to emerge from the Avon Longitudinal Study of Parents and Children, which enrolled 14,000 pregnant mothers between 1991 and 1992 and has since followed their children's development in minute detail. The study is funded by the Medical Research Council, the Wellcome Trust and Bristol University.

Vitamin D: The key to taller babies

Vitamin D is created by the action of sunlight on the skin and levels in all British residents are at their lowest at this time of year, in mid-winter. Short days and grey skies mean 60 per cent of the British population are deficient by the start of spring.

A 40-year review of research found that a daily dose could halve the risk of breast and colon cancer. It has also been shown to play a vital role in protecting against heart disease, cancer, diabetes and high blood pressure as well as being essential for bone health. Widespread deficiency in vitamin D among populations in the northern hemisphere suggests it may account for several thousand premature deaths from cancers alone. Twenty minutes in the sun, with the hands, arms and face exposed, is all that is needed to get an adequate dose, but it needs to be regularly topped up. In winter the only way of maintaining levels is by taking cod liver oil or supplements.

Jeremy Laurance

Suggested Topics
Start your day with The Independent, sign up for daily news emails
ebooks
ebooksAn introduction to the ground rules of British democracy
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
SPONSORED FEATURES
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Telesales Executive - OTE £25,000

£13000 - £25000 per annum: Recruitment Genius: Would you like to be part of a ...

Recruitment Genius: 1st Line Technical Support Engineer

£19000 - £23000 per annum: Recruitment Genius: This IT and Telecoms company ar...

Recruitment Genius: Assistant Manager - Visitor Fundraising

£23000 per annum: Recruitment Genius: The Visitor Fundraising Team is responsi...

Recruitment Genius: Developer

£30000 - £35000 per annum: Recruitment Genius: This is an opportunity to join ...

Day In a Page

The Silk Roads that trace civilisation: Long before the West rose to power, Asian pathways were connecting peoples and places

The Silk Roads that trace civilisation

Long before the West rose to power, Asian pathways were connecting peoples and places
House of Lords: Outcry as donors, fixers and MPs caught up in expenses scandal are ennobled

The honours that shame Britain

Outcry as donors, fixers and MPs caught up in expenses scandal are ennobled
When it comes to street harassment, we need to talk about race

'When it comes to street harassment, we need to talk about race'

Why are black men living the stereotypes and why are we letting them get away with it?
International Tap Festival: Forget Fred Astaire and Ginger Rogers - this dancing is improvised, spontaneous and rhythmic

International Tap Festival comes to the UK

Forget Fred Astaire and Ginger Rogers - this dancing is improvised, spontaneous and rhythmic
War with Isis: Is Turkey's buffer zone in Syria a matter of self-defence – or just anti-Kurd?

Turkey's buffer zone in Syria: self-defence – or just anti-Kurd?

Ankara accused of exacerbating racial division by allowing Turkmen minority to cross the border
Doris Lessing: Acclaimed novelist was kept under MI5 observation for 18 years, newly released papers show

'A subversive brothel keeper and Communist'

Acclaimed novelist Doris Lessing was kept under MI5 observation for 18 years, newly released papers show
Big Blue Live: BBC's Springwatch offshoot swaps back gardens for California's Monterey Bay

BBC heads to the Californian coast

The Big Blue Live crew is preparing for the first of three episodes on Sunday night, filming from boats, planes and an aquarium studio
Austin Bidwell: The Victorian fraudster who shook the Bank of England with the most daring forgery the world had known

Victorian fraudster who shook the Bank of England

Conman Austin Bidwell. was a heartless cad who carried out the most daring forgery the world had known
Car hacking scandal: Security designed to stop thieves hot-wiring almost every modern motor has been cracked

Car hacking scandal

Security designed to stop thieves hot-wiring almost every modern motor has been cracked
10 best placemats

Take your seat: 10 best placemats

Protect your table and dine in style with a bold new accessory
Ashes 2015: Alastair Cook not the only one to be caught in The Oval mindwarp

Cook not the only one to be caught in The Oval mindwarp

Aussie skipper Michael Clarke was lured into believing that what we witnessed at Edgbaston and Trent Bridge would continue in London, says Kevin Garside
Can Rafael Benitez get the best out of Gareth Bale at Real Madrid?

Can Benitez get the best out of Bale?

Back at the club he watched as a boy, the pressure is on Benitez to find a winning blend from Real's multiple talents. As La Liga begins, Pete Jenson asks if it will be enough to stop Barcelona
Athletics World Championships 2015: Beijing witnesses new stage in the Jessica Ennis-Hill and Katarina Johnson-Thompson heptathlon rivalry

Beijing witnesses new stage in the Jess and Kat rivalry

The last time the two British heptathletes competed, Ennis-Hill was on the way to Olympic gold and Johnson-Thompson was just a promising teenager. But a lot has happened in the following three years
Jeremy Corbyn: Joining a shrewd operator desperate for power as he visits the North East

Jeremy Corbyn interview: A shrewd operator desperate for power

His radical anti-austerity agenda has caught the imagination of the left and politically disaffected and set a staid Labour leadership election alight
Isis executes Palmyra antiquities chief: Defender of ancient city's past was killed for protecting its future

Isis executes Palmyra antiquities chief

Robert Fisk on the defender of the ancient city's past who was killed for protecting its future