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
News
ebooksAn unforgettable anthology of contemporary reportage
Life and Style
Angel Di Maria is shown the red card
tech
Sport
Roger Federer after his win over Tomas Berdych
sport
Life and Style
News in briefs: big pants in 'Bridget Jones's Diary'
fashionBig knickers are back
Sport
James Milner is set to sign for Liverpool this week despite rival interest from Arsenal
sportReds baulk at Benteke £32.5m release clause
News
The controversial Motor Neurone Disease Association poster, featuring sufferer Michael Smith, has drawn a series of angry complaints
newsThis one has been criticised for its 'threatening tone'
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

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

iJobs Job Widget
iJobs General

Recruitment Genius: Account Executive - Graduate / Entry Level

£22000 - £27500 per annum: Recruitment Genius: This digital advertising infras...

Recruitment Genius: European Sales Director - Aerospace Cable & Wire

£100000 - £125000 per annum: Recruitment Genius: As a top tier supplier to the...

Recruitment Genius: Digital Project Manager

£17100 - £22900 per annum: Recruitment Genius: One of the North West's leading...

Recruitment Genius: IT Support Technician

£20000 - £22000 per annum: Recruitment Genius: This is an intermediate help de...

Day In a Page

On your feet! Spending at least two hours a day standing reduces the risk of heart attacks, cancer and diabetes, according to new research

On your feet!

Spending half the day standing 'reduces risk of heart attacks and cancer'
Liverpool close in on Milner signing

Liverpool close in on Milner signing

Reds baulk at Christian Benteke £32.5m release clause
With scores of surgeries closing, what hope is there for the David Cameron's promise of 5,000 more GPs and a 24/7 NHS?

The big NHS question

Why are there so few new GPs when so many want to study medicine?
Big knickers are back: Thongs ain't what they used to be

Thongs ain't what they used to be

Big knickers are back
Thurston Moore interview

Thurston Moore interview

On living in London, Sonic Youth and musical memoirs
In full bloom

In full bloom

Floral print womenswear
From leading man to Elephant Man, Bradley Cooper is terrific

From leading man to Elephant Man

Bradley Cooper is terrific
In this the person to restore our trust in the banks?

In this the person to restore our trust in the banks?

Dame Colette Bowe - interview
When do the creative juices dry up?

When do the creative juices dry up?

David Lodge thinks he knows
The 'Cher moment' happening across fashion just now

Fashion's Cher moment

Ageing beauty will always be more classy than all that booty
Thousands of teenage girls enduring debilitating illnesses after routine school cancer vaccination

Health fears over school cancer jab

Shock new Freedom of Information figures show how thousands of girls have suffered serious symptoms after routine HPV injection
Fifa President Sepp Blatter warns his opponents: 'I forgive everyone, but I don't forget'

'I forgive everyone, but I don't forget'

Fifa president Sepp Blatter issues defiant warning to opponents
Extreme summer temperatures will soon cause deaths of up to 1,700 more Britons a year, says government report

Weather warning

Extreme summer temperatures will soon cause deaths of up to 1,700 more Britons a year, says government report
LSD: Speaking to volunteer users of the drug as trials get underway to see if it cures depression and addiction

High hopes for LSD

Meet the volunteer users helping to see if it cures depression and addiction
German soldier who died fighting for UK in Battle of Waterloo should be removed from museum display and given dignified funeral, say historians

Saving Private Brandt

A Belgian museum's display of the skeleton of a soldier killed at Waterloo prompts calls for him to be given a dignified funeral