Mothers' diets may harm IQs in two-thirds of babies

Most pregnant women are deficient in iodine, a mineral vital for cognitive development

Iodine deficiency is widespread amongst pregnant women in the UK and may be harming the cognitive development of their children, scientists have found.

The first large study of the problem in the UK has revealed that two-thirds of expectant mothers had a mild to moderate deficiency in the mineral, which was associated with significantly lower IQ and reading ability in their children at the ages of eight and nine.

Iodine is essential for growth and development of the brain, and pregnant women need 50 per cent more. Researchers said women should ensure they are getting enough from their diet – milk, yogurt and fish are the best sources – and that any pregnancy supplement they take contains iodine.

But they warned that kelp and seaweed supplements should be avoided as they contain variable levels of iodine and could lead to overdose. Severe iodine deficiency is known to cause brain damage and is the biggest cause of mental deficiency in the developing world. But mild to moderate iodine deficiency has been little studied – until now.

Researchers from the Universities of Surrey and Bristol examined records of 1,000 mothers who were part of the Children of the 90s study which has followed the development of children born to 14,000 mothers in Avon since 1990-91. They found that 67 per cent of the mothers had levels of iodine below that recommended by the World Health Organisation. Their children were divided into groups according to how well they performed on IQ and reading tests at eight and nine. The results showed those whose mothers had low iodine levels were 60 per cent more likely to be in the bottom group.

Children of mothers with low iodine scored six points lower on verbal IQ than those born to mothers with adequate iodine. Professor Jean Golding, founder of the Children of the 90s study, said the effect was large enough to influence exam grades later in life. “If iodine deficiency were rare I would not be so worried. But it is not rare. This may prevent a child reaching their full potential.”

Margaret Rayman, professor of nutritional medicine at the University of Surrey, who led the study published in The Lancet, said deficiency of iodine had been widespread in the UK until the 1960s. A change in farming practice led to iodine being added to winter cattle feed to boost milk yield in cows. Milk then became a good source of iodine, especially in winter, supplying 42 per cent of the population’s needs and it was assumed the UK had sufficient levels. However a Lancet study in 2011 found mild deficiency in schoolgirls in nine parts of the UK.

“You would expect to see a deficiency in women and girls. They don’t drink a lot of milk. Teenage girls are worried about their weight,” Professor Rayman said.

Conventional milk contained more iodine than organic milk, and white fish more than oily fish, she said. Recommended amounts for pregnant women were two portions of fish a week and three portions of dairy products a day. “If you are taking pregnancy supplements check the label – not all contain iodine. The recommended levels from all sources for pregnant and breastfeeding women are 250 micrograms of iodine a day, for adults 150 micrograms and for children 90-120 micrograms.”

Important iodine: Get the right amount

Pregnant and breastfeeding women, and those planning a pregnancy, need 250 micrograms daily. The best source is fish and dairy products. 

As a guide, two portions of fish a week and three portions of dairy products a day should be sufficient. Women taking pregnancy supplements are advised to choose ones containing iodine. The recommended amount is 140-150mcgs a day – the rest coming from diet. It is important not to have too much – more than 600mcgs a day can cause thyroid problems. Kelp and seaweed supplements should be avoided as they contain excessive amounts of iodine.           

Jeremy Laurance

Life and Style
ebookNow available in paperback
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

ES Rentals

    Independent Dating
    and  

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

    iJobs Job Widget
    iJobs General

    Guru Careers: Software Developer / C# Developer

    £40-50K: Guru Careers: We are seeking an experienced Software / C# Developer w...

    Guru Careers: Software Developer

    £35 - 40k + Benefits: Guru Careers: We are seeking a Software Developer (JavaS...

    SThree: Trainee Recruitment Consultant / Resourcer

    £18000 - £23000 per annum + Commission: SThree: As a Trainee Recruitment Consu...

    Ashdown Group: UI Developer - (UI, HTML, CSS, JavaScript, AngularJS)

    £25000 - £40000 per annum: Ashdown Group: UI Developer - (UI, JavaScript, HTML...

    Day In a Page

    Sun, sex and an anthropological study: One British academic's summer of hell in Magaluf

    Sun, sex and an anthropological study

    One academic’s summer of hell in Magaluf
    From Shakespeare to Rising Damp... to Vicious

    Frances de la Tour's 50-year triumph

    'Rising Damp' brought De la Tour such recognition that she could be forgiven if she'd never been able to move on. But at 70, she continues to flourish - and to beguile
    'That Whitsun, I was late getting away...'

    Ian McMillan on the Whitsun Weddings

    This weekend is Whitsun, and while the festival may no longer resonate, Larkin's best-loved poem, lives on - along with the train journey at the heart of it
    Kathryn Williams explores the works and influences of Sylvia Plath in a new light

    Songs from the bell jar

    Kathryn Williams explores the works and influences of Sylvia Plath
    How one man's day in high heels showed him that Cannes must change its 'no flats' policy

    One man's day in high heels

    ...showed him that Cannes must change its 'flats' policy
    Is a quiet crusade to reform executive pay bearing fruit?

    Is a quiet crusade to reform executive pay bearing fruit?

    Dominic Rossi of Fidelity says his pressure on business to control rewards is working. But why aren’t other fund managers helping?
    The King David Hotel gives precious work to Palestinians - unless peace talks are on

    King David Hotel: Palestinians not included

    The King David is special to Jerusalem. Nick Kochan checked in and discovered it has some special arrangements, too
    More people moving from Australia to New Zealand than in the other direction for first time in 24 years

    End of the Aussie brain drain

    More people moving from Australia to New Zealand than in the other direction for first time in 24 years
    Meditation is touted as a cure for mental instability but can it actually be bad for you?

    Can meditation be bad for you?

    Researching a mass murder, Dr Miguel Farias discovered that, far from bringing inner peace, meditation can leave devotees in pieces
    Eurovision 2015: Australians will be cheering on their first-ever entrant this Saturday

    Australia's first-ever Eurovision entrant

    Australia, a nation of kitsch-worshippers, has always loved the Eurovision Song Contest. Maggie Alderson says it'll fit in fine
    Letterman's final Late Show: Laughter, but no tears, as David takes his bow after 33 years

    Laughter, but no tears, as Letterman takes his bow after 33 years

    Veteran talkshow host steps down to plaudits from four presidents
    Ivor Novello Awards 2015: Hozier wins with anti-Catholic song 'Take Me To Church' as John Whittingdale leads praise for Black Sabbath

    Hozier's 'blasphemous' song takes Novello award

    Singer joins Ed Sheeran and Clean Bandit in celebration of the best in British and Irish music
    Tequila gold rush: The spirit has gone from a cheap shot to a multi-billion pound product

    Join the tequila gold rush

    The spirit has gone from a cheap shot to a multi-billion pound product
    12 best statement wallpapers

    12 best statement wallpapers

    Make an impact and transform a room with a conversation-starting pattern
    Paul Scholes column: Does David De Gea really want to leave Manchester United to fight it out for the No 1 spot at Real Madrid?

    Paul Scholes column

    Does David De Gea really want to leave Manchester United to fight it out for the No 1 spot at Real Madrid?