Benefits and risks of fish consumption in pregnancy
Submitting InstitutionUniversity of Ulster
Unit of AssessmentAllied Health Professions, Dentistry, Nursing and Pharmacy
Summary Impact TypeHealth
Research Subject Area(s)
Medical and Health Sciences: Nutrition and Dietetics, Paediatrics and Reproductive Medicine, Public Health and Health Services
Summary of the impact
Research undertaken at the University of Ulster has had a global impact
on public health advice about fish consumption during pregnancy. Ulster's
international collaborative research has been used by the Food and
Agriculture Organisation (FAO) of the United Nations and the World Health
Organization (WHO), and also by industry, to promote greater fish
consumption during pregnancy. The work has also been evaluated by the
European Food Safety Authority (EFSA) in its assessment of the public
health risk of methyl-mercury in food.
The Seychelles Child Development Study (SCDS) is a series of
epidemiological studies in mother-child cohorts recruited in the high
fish-eating population of the Seychelles. The key Ulster researchers are
Professor JJ Strain, Dr E McSorley (née Duffy), Dr Maria Mulhern (née
Barnes) and Dr Alison Yeates (née McAfee) who were employed at the
University of Ulster at the time the research was carried out, from 1999
onwards. The research programme was undertaken in collaboration with the
University of Rochester, New York and the Department of Health, Republic
of Seychelles. The results have been published in top nutrition and
It is crucial that pregnant women receive accurate advice on diet. Fish
exposes mothers to potentially high amounts of methyl-mercury, an
environmental pollutant and toxicant to which the developing foetal brain
is particularly sensitive. Government advisories worldwide have cautioned
pregnant women to limit their fish consumption. This advice is based on
limited epidemiological evidence; for example, in the Faroe Islands a
study which found detrimental effects on children's neurodevelopment, was
linked to maternal consumption during pregnancy of pilot whalemeat which
is high in methyl-mercury.
However fish is an excellent source of protein and essential nutrients.
It is the primary source of n-3 (omega-3) polyunsaturated fatty acids
(PUFA), particularly docosahexaenoic acid (DHA), which are important for
brain development. Limiting maternal fish intake could therefore pose a
threat to children's optimal neurological development. Moreover, in many
communities worldwide, fish is the predominant source of protein and other
A resolution of this dilemma comes from studies involving the high
fish-eating population of the Republic of Seychelles. The Seychelles Child
Development Study (Main Cohort), originally set up in 1989, recruited
pregnant women and continues to follow their offspring. It was designed to
determine if prenatal exposure to methyl-mercury had a detrimental effect
on offspring's neurodevelopment. In fact it found positive associations
between maternal methyl-mercury exposure and developmental outcomes in the
children, but the reasons for this association were unclear given that
methyl-mercury is a toxin. A further study (SCDS Nutrition Cohort) was set
up to see if nutritional factors could explain this positive association.
This study involved the recruitment of 300 mothers during pregnancy and
has continued to observe 229 mother-child pairs. It measured the women
during pregnancy both for methyl-mercury exposure and a number of
nutritional factors which are known to influence child development; the
cognitive development of the offspring has been measured at various stages
of their childhood.
The study found positive associations between the maternal intakes of n-3
PUFA (and especially DHA) from fish consumption during pregnancy, and the
developmental outcomes in the children. These associations were shown in
the children at 9 months, 30 months and 5 years of age and these findings
may also explain the positive associations between maternal methyl-mercury
exposure and developmental outcomes found in the SCDS Main Cohort.
Our conclusion was that maternal nutrition has played a confounding role
in these epidemiological studies.
Potentially detrimental effects of maternal methyl-mercury exposure
(negative associations with developmental outcomes in the child) in the
SCDS Nutrition Cohort were only evident at 30 months of age and only when
the n-3 PUFA measures were included as covariates in the regression
analyses. Such negative associations have not been found up to 17 years of
age among the offspring from the SCDS Main Cohort.
The work indicates that the beneficial effects of the n-3 PUFA present in
fish can outweigh any adverse effects of prenatal methyl-mercury exposure
on neurodevelopmental outcomes in children. Indeed, these beneficial
effects were observed with fish intakes up to two meals per day. This
level of fish consumption in this sentinel population is much higher than
that consumed by pregnant women in Western countries.
Key Researchers at Ulster:
Key staff: Professor JJ (Sean) Strain (Professor of Human
Nutrition and Director of NICHE; 1981-present); Dr Emeir McSorley (née
Duffy) (Senior Lecturer; 2002-present); Dr Maria Mulhern (née Barnes)
(Lecturer; 2007-present); Dr Alison Yeates (née McAfee) (Research
Associate 2009-present); Professor Julie Wallace (Professor; deceased)
References to the research
Strain, J.J., Davidson, P. W., Thurston, S. W., Harrington, D., Mulhern,
M. S., McAfee, A. J., van Wijngaarden, E., Shamlaye, C. F., Henderson, J.
and Watson, G. E. (2012). Maternal PUFA status but not prenatal
methylmercury exposure is associated with children's language functions at
age five years in the Seychelles. Journal of Nutrition, 142(11):
|Times Cited: 6
||Impact Factor: 3.916
Paper also selected for pubcast:
Video Pubcast, Scivee (in association with American Society of
Nutrition) (October 2012):
Maternal Polyunsaturated Fatty Acid Status but not Prenatal
Methylmercury exposure is associated with Children's Language Functions
at Age Five Years in the Seychelles
Available at: http://www.scivee.tv/node/53926
1024 views (as of 08/09/2013)
Davidson, P. W., Cory-Slechta, D. A., Thurston, S. W., Huang, L.-S.,
Shamlaye, C. F., Gunzler, D., Watson, G., van Wijngaarden, E., Zareba, G.,
Klein, J. D., Clarkson, T. W., Strain, J. J. and Myers, G. J. (2011). Fish
consumption and prenatal methylmercury exposure: Cognitive and behavioral
outcomes in the main cohort at 17 years from the Seychelles child
development study. Neurotoxicology, 32(6): 711-717.
|Times Cited: 14
||Impact Factor: 3.096
Lynch, M. L., Huang, L.-S., Cox, C., Strain, J. J., Myers, G. J., Bonham,
M. P., Shamlaye, C. F., Stokes-Riner, A., Wallace, J. M. W.,
Duffy, E. M., Clarkson, T. W. and Davidson, P. W. (2011). Varying
coefficient function models to explore interactions between maternal
nutritional status and prenatal methylmercury toxicity in the Seychelles
Child Development Nutrition Study. Environmental Research, 111(1):
|Times Cited: 7
||Impact Factor: 3.398
Stokes-Riner, A., Thurston, S. W., Myers, G. J., Duffy, E. M., Wallace,
J., Bonham, M., Robson, P., Shamlaye, C. F., Strain, J. J., Watson, G. and
Davidson, P. W. (2011). A longitudinal analysis of prenatal exposure to
methylmercury and fatty acids in the Seychelles. Neurotoxicology and
Teratology, 33(2): 325-328.
|Times Cited: 12
||Impact Factor: 2.983
Davidson, P. W., Strain, J. J., Myers, G. J., Thurston, S. W., Bonham, M.
P., Shamlaye, C. F., Stokes-Riner, A., Wallace, J. M. W., Robson, P. J.,
Duffy, E. M., Georger, L. A., Sloane-Reeves, J., Cernichiari, E.,
Canfield, R. L., Cox, C., Huang, L. S., Janciuras, J. and Clarkson, T. W.
(2008). Neurodevelopmental effects of maternal nutritional status and
exposure to methylmercury from eating fish during pregnancy. Neurotoxicology,
|Times Cited: 51
||Impact Factor: 3.096
Strain, J. J., Davidson, P. W., Bonham, M. P., Duffy, E. M.,
Stokes-Riner, A., Thurston, S. W., Wallace, J. M. W., Robson, P. J.,
Shamlaye, C. F., Georger, L. A., Sloane-Reeves, J., Cernichiari, E.,
Canfield, R. L., Cox, C., Huang, L. S., Janciuras, J., Myers, G. J. and
Clarkson, T. W. (2008). Associations of maternal long-chain
polyunsaturated fatty acids, methyl mercury, and infant development in the
Seychelles Child Development Nutrition Study. Neurotoxicology,
|Times Cited: 52
||Impact Factor: 3.096
Grant income obtained to undertake the studies was from the US
National Institutes of Health (NIH) and the European Commission (EC):
Strain, J. J., Wallace, J. M. W., Duffy, E. M., Mulhern, M. and McAfee,
A. Methyl mercury effects on adolescent development. Funded by grant
5-R01- ES008442 US National Institute of Environmental Health Sciences,
NIH; 2011-2015; £200k.
Strain, J. J., Chang, C. K., Wallace, J. M. W. and Duffy, E. M. Toxicity
of methyl mercury in a fish-eating population. Funded by grant
5-R01-ES010219 US National Institute of Environmental Health Sciences,
NIH; 2010-2014; £710k.
Strain, J. J., Bonham, M. P., Wallace, J. M. W., Duffy, E. M., Rowland,
I. and Livingstone, M.B.E. Public health impact of low-level mixed element
exposure in susceptible population strata (PHIME). Funded by grant from
the EC through its Sixth Framework Programme for RTD (contract no
FOOD-CT-2006-016253); 2006-2011; £445k.
Strain, J. J., Wallace, J. M. W., Robson, P. J., Rowland, I. and
Livingstone, M. B. E. Factors modifying the toxicity of methyl mercury in
a fish eating population. Funded by grant 5-R01 - ES010219 US National
Institute of Environmental Health Sciences, NIH; 2010-2014; £467k.
Details of the impact
Experts and global leaders in health matters have used the collaborative
research undertaken in the Seychelles by researchers at Ulster to revise
the guidelines on fish intake during pregnancy.
A report of the Joint FAO/WHO Expert Consultation on the Risks and
Benefits of Fish Consumption  concluded that maternal fish
consumption contributes to optimal neurodevelopment in their offspring and
that the neurodevelopment risks of not eating fish exceed the risks of
eating fish for up to at least seven 100g servings per week and
methyl-mercury concentrations up to at least 1 µ/g. Data from studies
undertaken in the SCDS were central to these conclusions and the work of
Davidson et al. 2008, Strain et al. 2008 and Lynch et
al. 2011 was cited in the report. This report was a landmark in
global recommendations for maternal advice on fish consumption during
pregnancy. Maternal advice in most countries has recommended that fish
intake should be limited during pregnancy because of the concerns of
methyl-mercury neurotoxicity to the foetus. The report recognised that
eating fish is part of the cultural traditions of many peoples and in some
populations fish is a major source of food and essential nutrients. This
report was the first time in an official advisory publication that the
direct benefits of the n-3 fatty acids, from fish eaten during pregnancy,
were indicated to outweigh any possible risks of methyl-mercury on child
Following the FAO/WHO report, the European Food Safety Authority (EFSA) 
was asked by the European Commission (EC) to consider these new
developments regarding methyl-mercury toxicity and evaluate whether the
Joint FAO/WHO Expert Committee on Food Additives (JECFA) provisional
tolerable weekly intakes (TWI) for methyl-mercury were still appropriate.
This request recognised that the SCDS Nutrition Cohort had indicated that
n-3 PUFA in fish may counteract any potential negative effects from
methyl-mercury exposure. It also recognised that beneficial nutrients in
fish may be the confounding factor that accounts for the positive outcomes
in the SCDS study compared with the adverse outcomes in previous child
cohort studies. In light of these findings, the Panel on Contaminants in
the Food Chain (CONTAM) established a revised TWI for methyl-mercury. The
Panel also concluded that, if measures to reduce methyl-mercury exposure
are considered, the potential beneficial effects of fish consumption
should also be taken into account. All six key references in section 2
were evaluated and used in this scientific opinion, which is being used by
the EC to update European recommendations.
In the most recent Dietary Guidelines for Americans 2010 , it
was appreciated that a variety of seafood in the amounts recommended
outweigh the health risks associated with methyl-mercury. There was some
relaxation, compared with the Advisory from the Environmental Protection
Agency (EPA), with respect to the advice given to pregnant women on fish
consumption. Women were still advised not to consume the fish with the
highest methyl-mercury content and limit consumption of white tuna because
of its methyl-mercury levels.
The work of the SCDS has also been cited in various websites associated
with industry  and websites giving advice to clinicians 
and health professionals [6-9], albeit citations to the specific
key references in section 2 are not always given.
The Seychelles Child Development Study is the largest epidemiological
prospective study of nutrition and toxicology. The results continue to
inform policymakers on the risk-benefit analysis of fish consumption
Sources to corroborate the impact
- FAO/WHO (2011). Report of the Joint FAO/WHO Expert Consultation on the
Risks and Benefits of Fish Consumption. Rome, Food and Agriculture
Organization of the United Nations; Geneva, World Health Organization,
Executive Summary available at:
http://www.who.int/foodsafety/chem/meetings/RBfish_exec_summary.pdf. Accessed March 2011.
- EFSA Panel on Contaminants in the Food Chain (2012) Scientific Opinion
on the risk for public health related to the presence of mercury and
methylmercury in food. EFSA Journal, 10(12):2985
- Dietary Guidelines Advisory Committee. (2010). Report of the
Dietary Guidelines Advisory Committee on the Dietary Guidelines for
Americans, 2010, to the Secretary of Agriculture and the Secretary of
Health and Human Services. U.S. Department of Agriculture,
Agricultural Research Service, Washington, DC.
- Food Product Design (08/01/13)Prenatal exposure to fish boosts child's
brain power http://www.foodproductdesign.com/news/2013/01/prenatal-exposure-to-fish-boosts-child-s-brain-po.aspx
- UpToDate (April 2012) Risks and benefits of fish consumption and fish
oil supplements during pregnancy. http://www.uptodate.com/contents/risks-and-benefits-of-fish-consumption-and-fish-oil-supplements-during-pregnancy
- Fats of Life (December 2012) Higher maternal PUFAs, not methylmercury,
associated with language scores at age 5. PUFA Newsletter 17(3) 16-18.
- Fats of Life (April 2012) Maternal and infant health: Unimpaired
neurodevelopment in adolescents of mothers with high prenatal fish and
methylmercury intakes. PUFA Newsletter 17(1) 5-6.
- Fats of Life (September 2008) Maternal and infant health: Interplay
between nutrients and methylmercury in child neurodevelopment. PUFA
newsletter 13(3) 15-17.
- Omega-3 Centre (December 2012) Nutrients in fish can boost brain
development The Omega-3 Centre: e-newsletter 11.