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Recommend -3 fatty acids in pregnancy?

Thank you for your Motherisk Update on -3 fatty acid supplementation during pregnancy.¹ I agree that the essential fatty acids linoleic acid, -linolenic acid, docosahexaenoic acid (DHA), eicosapentenoic acid, and arachidonic acid are all essential components of the human brain and are all required for normal brain development and function.

It is important to remember the effects of -3 fatty acids on cell and cell membrane function. Docosahexaenoic acid has "significant effects on photoreceptor membranes and neurotransmitters involved in the signal transduction process; rhodopsin activation, rod and cone development, neuronal dendritic connectivity, and functional maturation of the central nervous system."²

I also agree that -3 fatty acids benefit preeclampsia, or pregnancy-induced hypertension, in observational studies. Reference ^10,3 however, is used in the article for both observational and interventional trials. Which is it?

Second, reference ¹¹⁴ is used in the article to indicate that this interventional trial does not support benefit in preventing preeclampsia, when the opposite is true. This article showed improvement in gestational age (primary outcome) by about 6 days, which was statistically significant. It also showed improvement of birth weight (primary outcome), length, and head circumference (secondary outcomes), but these improvements were not statistically significant. Preeclampsia was not discussed beyond being listed in Table 3 of the article. Those taking high levels of DHA (interventional group) had a relative risk reduction of about 50% for developing preeclampsia and the number needed to treat to prevent 1 case of preeclampsia was 30, which certainly favours some benefit. Please explain.

The recent study⁵ that shows potential harm from -3 fatty acids and fish consumption is done in a community that traditionally has a high fish intake and might have an unaccounted confounder. Background levels of methylmercury were not taken in this population—a major concern in similar populations.⁶ It is recognized that hypertension has been induced by chronic ingestion of methylmercury among rats.⁷ Human exposure is a relatively new area of medicine and information is exploding at this time. The reason for the adverse outcome of the study might relate to toxicity, a point not mentioned in the article.

Third, I am disturbed by the conclusion of the article that no recommendations should be made to encourage women to take -3 fatty acid supplements. It has been estimated that the brain alone accumulates 67 mg DHA daily in the third trimester.⁸ Canada was the first country to recommend fatty acid intake, and international guidelines have been making recommendations since 1999. The International Society for the Study of Fatty Acids and Lipids, a scientific society, recommends adequate intakes of 4.44 g of linoleic acid and 2.22 g of -linolenic acid, with 0.22 g of DHA and 0.22 g of eicosapentenoic acid for adults and 0.3 g of DHA daily for pregnant women.⁹ Two excellent studies in Canada have shown that women rarely achieve these intakes and that more than 80% do not meet these requirements.^10,11 If Canadian women are deficient in DHA, if women are choosing to limit seafood intake in pregnancy because of public health warnings about toxicant exposure,¹² and if DHA is absolutely required for fetal brain development as the article correctly states, where do the authors propose that pregnant women obtain these required nutrients other than through supplementation? Public health recommendations have been discussed in other articles on this important topic.¹³

Finally, it would be appreciated if all sources of funding (including industry support) to the individual authors and the Motherisk program, as well as potential conflicts of interest, were fully disclosed in the article as is standard protocol with medical journals.

	References

TOP References

 

1. Dubnov-Raz G, Finkelstein Y, Koren G. -3 fatty acid supplementation during pregnancy. For mother, baby, or neither? Can Fam Physician 2007;53:817-8.[Abstract/Free Full Text]
2. Uauy R, Hoffman DR, Peirano P, Birch DG, Birch EE. Essential fatty acids in visual and brain development. Lipids 2001;36(9):885-95.[Medline]
3. Makrides M, Gibson RA. Long-chain polyunsaturated fatty acid requirements during pregnancy and lactation. Am J Clin Nutr 2000;71(1 Suppl):307S-11S.[Abstract/Free Full Text]
4. Smuts CM, Huang M, Mundy D, Plasse T, Major S, Carlson SE. A randomized trial of docosahexaenoic acid supplementation during the third trimester of pregnancy. Obstet Gynecol 2003;101(3):469-79.[Medline]
5. Olafsdottir AS, Skuladottir GV, Thorsdottir I, Hauksson A, Thorgeirsdottir H, Steingrimsdottir L. Relationship between high consumption of marine fatty acids in early pregnancy and hypertensive disorders in pregnancy. BJOG 2006;113(3):301-9.[Medline]
6. Hansen JC, Tarp U, Bohm J. Prenatal exposure to methyl mercury among Greenlandic polar Inuits. Arch Environ Health 1990;45(6):355-8.[Medline]
7. Wakita Y. Hypertension induced by methyl mercury in rats. Toxicol Appl Pharmacol 1987;89(1):144-7.[Medline]
8. Clandinin MT, Chappell JE, Heim T, Swyer PR, Chance GW. Fatty acid utilization in perinatal de novo synthesis of tissues. Early Hum Dev 1981;5(4):355-66.[Medline]
9. Simopoulos AP, Leaf A, Salem N Jr. Workshop on the essentiality of and recommended dietary intakes for omega-6 and omega-3 fatty acids. J Am Coll Nutr 1999;18(5):487-9.[Free Full Text]
10. Innis SM, Elias SL. Intakes of essential n-6 and n-3 polyunsaturated fatty acids among pregnant Canadian women. Am J Clin Nutr 2003;77(2):473-8.[Abstract/Free Full Text]
11. Denomme J, Stark KD, Holub BJ. Directly quantitated dietary (n-3) fatty acid intakes of pregnant Canadian women are lower than current dietary recommendations. J Nutr 2005;135(2):206-11.[Abstract/Free Full Text]
12. US Department of Health and Human Services, US Environmental Protection Agency. What you need to know about mercury in fish and shellfish. EPA and FDA advice for women who might become pregnant, women who are pregnant, nursing mothers, and young children. Rockville, MD: Food and Drug Administration; 2004. Available from: www.cfsan.fda.gov/~dms/admehg3.html. Accessed 2007 Mar 9 2004.
13. Genuis SJ, Schwalfenberg GK. Time for an oil check: the role of essential omega-3 fatty acids in maternal and pediatric health. J Perinatol 2006;26(6):359-65.[Medline]

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