Marine oils, such as fish oil or algal oil, are a rich source of omega-3 fatty acids, especially the essential fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Algal oil is high in DHA and low in EPA, whereas fish oil has more EPA than DHA. The DHA level in breastmilk is typically between 0.2% and 0.3% in Western countries.[1]
Fish oil up to 3 grams daily is “generally recognized as safe” (GRAS) as a food by the U.S. Food and Drug Administration. Current dietary recommendations for nursing mothers is 250 to 375 mg daily of DHA plus EPA.[2] Lactating women require a daily dosage of about 1 gram DHA plus EPA to reach a milk DHA plus EPA of 1 gram/dL at 4 weeks postpartum. This is usually sufficient to meet the DHA requirements of term breastfed infants, but not the higher requirements of preterm infants, where additional maternal supplementation is needed.[3] Maternal diet determines breastmilk levels of DHA and EPA and supplementation increases them within hours after supplementation, although ongoing milk concentrations depend more on long-term than short-term (past 3-days) intake.[4-8] Higher milk levels result in higher infant plasma and erythrocyte levels of omega-3 fatty acid-derived phospholipid. One study found that breastmilk DHA was a better predictor of infant erythrocyte DHA than direct supplementation of the infants with fish oil.[9] Higher levels of DHA in breastmilk are consistently linked to better motor, cognitive, and behavioral outcomes and a reduced risk of allergic disease in early childhood.[10]
Supplementation with omega-3 fatty acids has been studied for improving various infant outcomes. An international panel of experts concluded that DHA supplementation during breastfeeding is desirable.[11] Several meta-analyses have been performed on fish oil supplementation during breastfeeding.[12-16] The most recent and comprehensive meta-analysis found that maternal supplementation with omega-3-polyunsaturated fatty acids during lactation improved language ability.[15,16] Two meta-analyses found that maternal supplementation with omega-3-polyunsaturated fatty acids during lactation had little or no beneficial effect on childhood allergic diseases.[17,18] Although DHA supplementation increases anti-inflammatory components and reduced inflammatory prostaglandins in milk, supplementation of mothers with preterm infants did not decrease the frequency of bronchopulmonary dysplasia at 36 weeks gestational age.[19,20] Weak evidence for improved vision and attention was found in one study.[12,13] Long-term follow-up of a small group of children whose mothers received fish oil supplements during lactation found that boys had a delayed puberty, shorter average height, and higher systolic blood pressure at age 13 years, but no differences in self-rated socioemotional outcomes or physical activity at 13 years of age.[21,22] Infants breastfed by overweight or obese mothers who took 3 grams of fish oil daily had greater ponderal index and reduced insulin resistance compared to placebo at 3 months of age.[23] Other studies found that maternal fish oil supplementation during pregnancy and lactation reduced oxidative stress in their breastfed infants.[24,25] Supplementation of nursing mothers with fish oil of about 800 mg of DHA plus EPA for 6 months altered the infant intestinal microbiome in a way that might decrease resistance to colonization with pathogens; however, no increase in infant illnesses were seen.[26] Another study found that supplementing mothers with DHA during the third trimester of pregnancy and for 6 weeks postpartum increased the prevalence of Lactobacillus in the intestinal tracts of the mothers and their breastfed infants.[27] A meta-analysis of 35 randomized, controlled trials found that women with a diagnosis of severe depression obtained benefit from omega-3 fatty acids, but those with mild depression did not.[28] The most common complaint while taking fish oil is burping a fishy taste after ingestion. However, breast milk odor is not changed by maternal fish oil consumption.[29]
Dietary supplements do not require extensive pre-marketing approval from the U.S. Food and Drug Administration. Manufacturers are responsible to ensure the safety, but do not need to prove the safety and effectiveness of dietary supplements before they are marketed. Dietary supplements may contain multiple ingredients, and differences are often found between labeled and actual ingredients or their amounts. A manufacturer may contract with an independent organization to verify the quality of a product or its ingredients, but that does not certify the safety or effectiveness of a product. Because of the above issues, clinical testing results on one product may not be applicable to other products. More detailed information about dietary supplements is available elsewhere on the LactMed Web site.