The review called into question the evidence for all nutrients apart from vitamin D and folic acid – and pressed for greater availability of low-cost tablets containing these two nutrients and vitamin C.
Published in the British Medical Journal’s Drug and Therapeutics Bulletin, the review warned that some pregnant women were being manipulated by the marketing of complex multivitamin and mineral preparations, which were “unlikely to be needed” if the women had a healthy balanced diet.
Best start in life, whatever the cost
It stated: “The marketing of such products does not appear to be supported by evidence of improvement in child or maternal outcomes. Pregnant women may be vulnerable to messages about giving their baby the best start in life, regardless of cost, and be unaware that the only supplements recommended for all women during pregnancy are folic acid and vitamin D, which are available at relatively low cost.”
Major UK health food retailer Holland & Barrett has a whole section on its website for pregnancy supplements. One such multivitamin on sale costs about £15 (€17.80) for a month’s worth of tablets.
Meanwhile, nearly nine months worth of folic acid tablets cost £7.99 (€9.48).
Weighing up the evidence – or lack of
The researchers said they found “no evidence” to recommend that all pregnant women should take prenatal multi-nutrient supplements beyond folic acid and vitamin D supplements.
The strongest evidence of all was for folic acid, they said.
In the UK a daily dose of 400 µg daily is recommended for women first starting to try for a baby until 12 weeks of pregnancy to reduce the risk of neural tube defects (NTDs), with a higher daily dose of 5 mg recommended for women with a higher NTD risk for the infant.
“The evidence for vitamin D supplementation for all pregnant women is less clear cut, with little randomised controlled trial evidence supporting an effect on clinical outcomes,” the researchers wrote.
“Nevertheless, a dose of 10 µg vitamin D daily is recommended throughout pregnancy and breastfeeding (with a higher dose suggested for some women).”
Evidence for other vitamin supplements “does not show clear benefit for clinical outcomes” for most women who are well nourished, they said.
Meanwhile women should avoid taking vitamin A supplements during pregnancy.
Industry responds: Misleading and dangerous
The study has been highly publicised in the mainstream UK press, with a press release published on science news wire EurekAlert yesterday entitled ‘Multivitamin and mineral supplements for mums-to-be are needless expense’.
UK industry group the Health Food Manufacturers’ Association (HFMA) called this title “misleading”, particularly for at-risk groups where uptake of pregnancy and pre-conception supplementation is already low, “leading to a very real danger to the health of UK mothers-to-be and their unborn children”.
The group said this was particularly misleading on iodine, calcium and iron, intakes of which a UK National Diet and Nutrition Survey had shown were inadequate for a “substantial proportion of women of child bearing age” not just for low-income countries as suggested in the paper.
HFMA also rebuked conclusions on vitamin B12, which has been suggested as a strategy in combination with folic acid against NTDs.
“Although there have been many attempts by the government to raise awareness of the huge importance of pregnancy and pre-pregnancy nutrition, uptake of essential supplementation remains low, and messages need to be reinforced with women of a childbearing age, stories such as this one add unnecessary and potentially harmful confusion to Department of Health recommendations,” it said.
“Ideally, we would all get sufficient nutrients from a healthy diet, but for a large proportion of the population, and for certain at-risk groups, such as pregnant women, this is simply not the case. For these groups, the belief they can obtain all the nutrients necessary from the average UK diet poses a very real risk to the health of both mothers and their unborn children.”
Pregnancy health claims
In the EU there is an approved health claim for folic acid stating: “Supplemental folic acid intake increases maternal folate status. Low maternal folate status is a risk factor in the development of neural tube defects in the developing foetus.”
Omega-3 was not mentioned in the review – despite being backed by European Food Safety Authority (EFSA)-approved health claims for docosahexaenoic acid (DHA) maternal intake and the foetus' and breastfed infants' brain and eye development.
There is also an approved claim for iron in the EU for the “normal cognitive development of children”, although this claim does not refer to maternal intakes.
Source: Drug and Therapeutics Bulletin
Published online ahead of print, doi:10.1136/dtb.2016.7.0414
“Vitamin supplementation in pregnancy”