Executive Summary
The results of the recent studies among U.S. pregnant women prove that fish consumption during pregnancy benefits the cognition of the offspring in infancy but at the same time, high levels of mercury that fish contain have adverse effects on the cognition of little children. So, it is recommended to pregnant women to look for the fish species with a low level of mercury.
The issue whether pregnant women harm their babies or on the contrary benefit the child’s brain development while consuming fish is ambiguous. There has been a great quantity of researchers who have been studying this issue for many years and the result of their analysis must be used by government policymakers in the health sector. Maternal fish intake affects the natal development of a baby that may lead to dramatic consequences in future. The conflicting findings that state that fish consumption is potentially toxic to the babies because of severe mercury contamination but at the same time beneficial for the children during the natal period have created uncertainty among pregnant women about what they should do: do not eat fish at all, or if to consume fish then in what amount (in the United States of America, women are asked not to consume more seafood than 340 g per week during pregnancy).
The Results of the Recent Studies
Fish, as well as other seafood, are the main dietary sources of polyunsaturated fatty acids, including elongated omega-3. Sufficient consumption of elongated omega-3 during pregnancy is vital for the future health of a baby, as it may protect the fetal from harmful perinatal and longer-term outcomes. The docosahexaenoic acid that is contained in fish is highly important for optimal fetal neurodevelopment (Bloomingdale, A., Haines, J., Guthrie, L.B., Oken, E., 2016, 1234). Fish is a significant source of protein that is not otherwise available for many people. Fish is not only an excellent source of protein that provides numerous health benefits, but also, it includes omega-3 fatty acids that lower the level of cholesterol and reduces the possibility of heart disease and stroke (Burger, J., Gochfeld, M., 2008, 343). It is especially important to consume fish for pregnant women as it contributes to better cognitive development and prevents pre-term delivery. But such contaminants as mercury and polychlorinated biphenyls can also be found in some species of fish at high concentration. The developing brain of a baby is highly vulnerable to an environmental insult. During the 20th century, devastating exposures to mercury-contaminated seafood in Japan created the sensitivity of the babies to the toxic effects of mercury. The seafood and fish that is high in mercury pose a serious risk to the health of consumers, especially, to fetuses, neonates, developing infants and susceptible adults (Burger, J., Gochfeld, M., 2008, 343).
Experts have already worked out the guidelines for docosahexaenoic acid consumption by pregnant women and suggested the quantity of DHA that was considered optimal for maternal and child’s health but only 25 percent of women eat the recommended amount of DHA during pregnancy.
The US advisory, published in 2004, offers to consume not more than 340 g of fish per week aiming to reduce the negative effects of pollutants, like methylmercury, that can be found in seafood. But though methylmercury certainly harms a fetus’ brain, this harm is not greater than the loss of the benefits of nutrients that present in seafood. So, the advice to lessen the fish consumption may seem ambiguous as fish contains such healthy nutrients as iron, selenium, vitamin E, and n-3 polyunsaturated fatty acids that are necessary for right brain development. So, it is recommended to consume the species of fish that contain little mercury and enough beneficial nutrients. Generally, white meat fish, for example, haddock and cod, have low mercury levels, but at the same time, they are low in n-3 fatty acids, while dark meat fish, for example, mackerel and swordfish, contain a high amount of mercury as well as a high amount of n-3 fatty acids. Such fatty fish as canned light tuna and sardines contain relatively less mercury and more fatty acids.
According to the recent studies, a shark has the highest level of mercury. Bluefish includes more contaminants than any other species of fish. Striped bass, shark, tuna and bottom fish are also on the top list of fish species that are harmful to pregnant women (Burger, J., Gochfeld, M., 2008, 346).
The study has proved that the risk of the loss of the benefits of essential nutrients exceeds the risk of suffering from contaminants. Moreover, the statistics say that more mothers who consumed less than 340 g fish per week had children with suboptimum neurodevelopmental outcomes than the mothers who consumed more fish than it was recommended (Hibbeln, J.R., Davis, J.M., Steer, C., Emmett, P., Rogers, I., Williams, C., Golding, J., 2007, 584).
Also, the results of recent study prove that increased oily fish intake during pregnancy contributes to low quantity of bacteria of the Atopobiumcluster in the infants’ faeces during first 84 days after birth (Urwin, H. J., Diaper, N. D., Noakes, P.S., Yaqoob, P., 2013, 6).
The qualitative study of fish consumption has found out that pregnant women do not know what species of fish are harmful and what species of fish are recommended to consume. Most of them do not know anything about shellfish. Very few women had a discussion about fish consumption with an obstetrician. As most women knew about a possible harmful effect of fish intake, they refused eating fish during pregnancy but tried to receive DHA via supplements (Bloomingdale, A., Haines, J., Guthrie, L.B., Oken, E., 2016, 1237).
The study conducted in 2007 (Hibbeln, J.R., Davis, J.M., Steer, C., Emmett, P., Rogers, I., Williams, C., Golding, J., 2007, 578) showed that pregnant women who consumed less than 340 g of fish per week had babies with lower quartile for verbal IQ (overall trend, p=0·004) in comparison with the mothers who consumed more seafood than 340 g per week. Also, seafood intake by pregnant women was associated with higher risks of problems with the fine motor, social development, and communication. The study proved that the lower the intake of fish was during pregnancy, the higher the risks were of suboptimum developmental outcomes (Hibbeln, J.R., Davis, J.M., Steer, C., Emmett, P., Rogers, I., Williams, C., Golding, J., 2007, 578). It was also proved that in case pregnant women consumed less than 340 g of seafood per week, their children were not protected from an adverse outcome. It was recorded that in case a mother-to-be consumed more than 340 g of seafood per week, it had beneficial effects on the development of her child. Thus, it was proved that limiting the seafood intake could be detrimental for the baby. So, the risk from an insufficient amount of nutrients was greater than the risk to harm the baby with the trace contaminants contained in 340 g seafood that is consumed weekly.
The data that is obtained in ALSPAC proves that there is no evidence that intake of more than three portions of fish per week during pregnancy has a negative effect on the development of an infant. On the contrary, in case a pregnant woman consumes more than 340 g of fish every week, it will only benefit her baby’s neurodevelopment (Hibbeln, J.R., Davis, J.M., Steer, C., Emmett, P., Rogers, I., Williams, C., Golding, J., 2007, 583). If to advise pregnant women to limit seafood consumption, they may reduce the consumption of the nutrients that are necessary for the right neurological development. The study has found out that the less a mother-to-be consumes omega-3 fatty acid, the more chances her child will have lower verbal IQ. The list of outcomes that are associated with inadequate intake of omega-3 fatty acid during pregnancy is quite long and include retardation, intrauterine growth, adverse neurodevelopmental measures, delayed depth perception, deficits in fine motor skills, lower speed of information processing, and deficits in dopamine and serotonin release.
Another study found out that 7 percent of participants who eat more than 340 g of fish had babies with VRM scores 12.0 points higher than the pregnant women who eat less fish (Oken, E., Wright, R. O., Kleinman, K.P., Bellinger, D., Amarasiriwardena, C.J., Hu, H., Rich-Edwards, J.W., and Gillman, M. W., 2005, 1378). The study also proved that higher mercury exposure during pregnancy leads to low offspring cognitive score. Moreover, it is proved that maternal fish consumption protects babies from asthma (Salama, M.T., Lia, Y-F., Langholza, B., Gillilanda, F.D., 2009).
As some pregnant women have heard an advice to limit the amount of fish and they do not know what fish types are safe for their children, they may come to the conclusion that it would be better to avoid fish in order not to harm their infants. So, the results of the ALSPAC study should encourage pregnant women to eat more fish.
Such conflicting findings, that state that fish consumption is necessary for developing healthy fetus though it may be toxic at the same time, lead to an uncertainty among pregnant women. The only advice that can be made to women is to look for the species of fish that is low in mercury and at the same time high in docosahexaenoic acid and avoid consuming fish that is high in mercury.
Recommendations
There are several effective ways for coping with the problem of consuming harmful species of fish (Burger, J., Gochfeld, M., 2008, 348):
1. Till the environmental remediation and source reduction lessen the environmental burden of mercury, the main method of lessening the exposure to methylmercury should be making commercial and sport fish advisories.
2. A special risk communication campaign should provide detailed information about benefits and risks in order to let people make informed decisions. For instance, freshwater fishers should be targeted while they are buying fishing licenses. Though it is clear and undoubtedly that fish is an excellent source of protein and it gives a wide range of other health benefits, people should have enough information about the fish species that are high in contaminants, such as mercury, as well as they should know what species of fish provide high level of fish oils like omega-3. The studies found out that respondents lack basic and important information about the fish species that are contaminants. Most people do not know that predatory fish have a very high level of contaminants and that the level of contaminant gets higher with the size and age of fish. These facts will arm people with the proper information that will allow them to take right decisions while choosing fish dishes.
3. One more method of informing people about harmful and healthy fish is to publish a list of local subsistence and recreational species of fish and note the levels of PCBs and mercury, as well as the levels of healthy fish oils, like omega-3. Such information can be provided on small cards and carried by fishermen, given to people who cook fish dishes and for pregnant women. This will allow people take informed decisions and escape dramatic health problems.
Conclusion
The issue whether pregnant women harm their babies or on the contrary benefit the child’s brain development while consuming fish is ambiguous, as though fish includes fatty acids that are necessary for the right development of fetal brain, some fish species also include methylmercury – the demonstrated neurotoxin that has a significant negative influence on the brain development. According to the statistics, every tenth woman in the U.S.A. has mercury concentration higher than recommended. As it is clear that fish has high-dose mercury that harms the developing fetus, the U.S. advisory bodies have recommended pregnant women to limit fish consumption. But this advice is ambiguous because limiting the quantity of consumed fish, a pregnant woman limits the quantity of healthy microelements and vitamins that are essential for brain development of an infant. So, women are recommended to choose the species of fish that are low in mercury in order not to harm their babies and let them receive the healthy elements that fish contains.
References
Bloomingdale, A., Haines, J., Guthrie, L.B., Oken, E., 2016. A qualitative study of fish consumption during pregnancy. American Journal of Clinical Nutrition, pp. 1234-1240.
Burger, J., Gochfeld, M., 2008. Perceptions of the risks and benefits of fish consumption: Individual choices to reduce risk and increase health benefits. Environmental Research, 109 (2009), pp. 343 – 349.
Hibbeln, J.R., Davis, J.M., Steer, C., Emmett, P., Rogers, I., Williams, C., Golding, J., 2007. Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): an observational cohort study. Lancet, vol 369, pp. 578 – 585.
Oken, E., Wright, R. O., Kleinman, K.P., Bellinger, D., Amarasiriwardena, C.J., Hu, H., Rich-Edwards, J.W., and Gillman, M. W., 2005. Maternal Fish Consumption, Hair Mercury, and Infant Cognition in a U.S. Cohort. Children’s Health. Environmental Health Perspectives, 113 (10), pp. 1376 – 1380.
Salama, M.T., Lia, Y-F., Langholza, B., Gillilanda, F.D., 2009. Maternal Fish Consumption During Pregnancy and Risk of Early Childhood Asthma. Journal of Asthma. [Online] (updated 02 Jul 2009). Available at: http://www.tandfonline.com/doi/abs/10.1081/JAS-67619?journalCode=ijas20 [Accessed 5 May 2016].
Urwin, H. J., Diaper, N. D., Noakes, P.S., Yaqoob, P., 2013. Effect of salmon consumption during pregnancy on maternal and infant faecal microbiota, secretory IgA and calprotectin. The British journal of nutrition, pp. 1 – 12.
