Six months of exclusive breast feeding: how good is the evidence?

BMJ 2011; 342 doi: (Published 13 January 2011) Cite this as: BMJ 2011;342:c5955

When to start solids: what the WHO review actually found

Fewtrell et al have provoked a storm of indignation by their
suggestion that UK health authorities review the current policy on
starting solids and consider returning to a guideline to start between 4
and 6 months rather than the 6 months currently recommended (1). The 6-
month guideline is being hotly defended on the grounds that this is the
one recommended by the WHO's systematic review of the subject, but this is
misleading; the actual finding of the WHO review was that, for infants in
the developed world, there is not a great deal of difference between the
two guidelines.

Nearly all of the wide range of outcomes examined in the WHO review
were unaffected by whether infants started solids at six months or during
the preceeding couple of months. One study in the developing world (3)
found increased rates of respiratory infection in breastfed infants who
started solids earlier, but this was not found in infants in the developed
world (4). Another study found increased rates of eczema in the earlier
starters (5), but in this study the 'early starters' started at three
months, not four, and the findings were not replicated in the PROBIT trial
(4). Therefore, the only finding likely to be of relevance to
consideration of the effects of a 4 - 6-month guideline on infants in the
developed world is the increased rate of gastroenteritis in the infants
who started solids earlier than six months (4). While this rate was high
in the developing world (3), in the PROBIT trial it approximated to a 1 in
41 chance of gastroenteritis from starting mixed feeding between three and
six months, which may well overestimate possible adverse effects of a 4 -
6-month guideline since it will have included infants who started solids
between three and four months. Rates of hospitalisation for
gastroenteritis showed no statistically significant difference. Finally,
follow-up of the PROBIT study at 6.5 years found no long-term differences
between the earlier starters and the later starters (6).

The available evidence therefore suggests that the benefit of waiting
a full 6 months to start solids rather than starting them between 4 and 6
months is small and short-term at best. While I am quite happy to advise
parents that delaying solids until six months may slightly reduce the risk
of tummy bugs and thus it is worth aiming to do so if possible, I do feel
it is important to keep the matter in perspective. The furore in response
to Fewtrell et al's paper is out of all proportion to what the evidence
actually shows. We need to consider what effect this may be having on
parents who may be left unnecessarily concerned about the possible effects
on their infants of having started solids earlier than advised by the
current guidelines, as well as on parents who are currently facing the
decision as to when to start solids and need accurate information on which
to base this decision.

It is important to remember that health policies are not implemented
in a vacuum; they have practical implications for the lives of those
attempting to follow them. While these can be beneficial (it is worth
noting that the effects of later introduction of solids also include
greater ease of introduction, delayed resumption of maternal menses, and
slightly faster weight loss for the mother), there can also be
considerable potential difficulties in maintaining exclusivity of
breastfeeding for a full six months, especially for women returning to
work before this time. Mothers need to be able to weigh any such
drawbacks against the benefits of exclusive breastfeeding over mixed
breastfeeding. To do this, they need accurate information. Let's be
honest about what the evidence actually does show in terms of benefit or
lack thereof, and let parents make a fully informed choice for themselves
as to whether or not they find those two extra months of avoiding solids
or formula supplements worthwhile.

(1) Fewtrell M, Wilson DC, Booth I, Lucas A. Six months of exclusive
breast feeding: how good is the evidence? BMJ 2011; 342:c5955

(2) Kramer MS, Kakuma R. Optimal duration of exclusive breastfeeding.
Cochrane Database of Systematic Reviews 2002, Issue 1. Art. No.: CD003517.
DOI: 10.1002/14651858.CD003517.

(3) Khadivzadeh T, Parsai S. Effect of exclusive breastfeeding and
complementary feeding on infant growth and morbidity. East Mediterr
Health J 2004; 10(3): 289 - 94.

(4) Kramer MS, Guo T, Platt RW, Sevkovskaya Z, Dzikovich I, Collet
JP, et al. Infant growth and health outcomes associated with 3 compared
with 6 months of exclusive breastfeeding. Am J Clin Nutr 2003;78:291-5.

(5) Kajosaari M, Saarinen UM. Prophylaxis of atopic disease by six
months' total solid food elimination. Evaluation of 135 exclusively
breast-fed infants of atopic families. Acta Paediatr Scand 1983; 72: 411
- 4.

(6) Kramer MS, Matush L, Bogdanovich N, Aboud F, Mazer B, Fombonne E.
Health and development outcomes in 6.5-y-old children breastfed
exclusively for 3 or 6 mo. Am J Clin Nutr 2009; 90(4): 1070-4.

Competing interests: No competing financial interests. SCV breastfed both children successfully by expressing milk after returning to work, but had to supplement her first child with solids and formula from four months onwards.

02 February 2011
Sarah C. Vaughan