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. DHA and EPA are normal components of breastmilk where concentrations reflect maternal intake. The DHA level in breastmilk is typically between 0.2% and 0.3% in Western countries.[1] 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.[2] Maternal supplementation increases breastmilk levels of DHA and EPA, although it appears that milk concentrations depend more on long-term than short-term (past 3-days) intake.[3-5] 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.[6] Current dietary recommendations for nursing mothers is 250 to 375 mg daily of DHA plus EPA.[7] Lactating women require a daily dosage of about 1000 mg DHA plus EPA to reach a milk DHA plus EPA of 1 gram/dL at 4 weeks postpartum.[8]
Supplementation with omega-3 fatty acids has been studied for reduction of postpartum depression in nursing mothers and for improving various infant outcomes. 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.[9]
Several meta-analyses have been performed on fish oil supplementation during breastfeeding. They found no beneficial effect of omega-3-fatty acid supplementation during breastfeeding on infant problem-solving ability, intelligence, socioemotional, psychomotor or motor development, visual acuity, growth or language development, academic performance, risks of attention deficit disorder, attention deficit/hyperactivity disorder, autism spectrum disorder, anxiety, or depression.[10-13] The most recent and comprehensive meta-analysis found that supplementation improved measures of cognitive development in the infant or child by 6 to 11%.[13] 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.[14,15] A more recent large study found that supplementation of nursing mothers with DHA 1.2 grams daily did not improve their infants’ neurodevelopmental outcomes at 18 to 22 months of age in breastfed, preterm neonates, but subgroup analyses suggested a potential benefit for language in preterm neonates born before 27 weeks’ gestational age.[16] 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.[17,18]
Weak evidence for improved vision and attention was found in one study.[10,11] 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.[19,20] Other studies found that maternal fish oil supplementation during pregnancy and lactation reduced oxidative stress in their breastfed infants.[21,22] 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.[23] 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.[24]
Fish oil up to 3 grams daily is “generally recognized as safe” (GRAS) as a food by the U.S. Food and Drug Administration. The most common complaint is burping a fishy taste after ingestion. However, breast milk odor is not changed by maternal fish oil consumption.[25] Rarely, allergic reactions are reported with nut oil-derived omega-3 fatty acids in patients allergic to nuts.
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.