Although breast milk is the preferred source of infant nutrition, epidemiological studies have shown that docosahexaenoic acid (DHA) levels in breast milk are highly dependent upon the geographical location of the female population under study and the related habitual diet of the population, with the highest DHA levels in N. American Inuit and in some Asian populations. [1. Fu Y, Liu X, Zhou B, Jiang AC, Chai L. 2016 An updated review of worldwide levels of docosahexaenoic and arachidonic acid in human breast milk by region. Public Health Nutr.;19(15):2675-87.], [2. Brenna JT, Varamini B, Jensen RG, Diersen-Schade DA, Boettcher JA, Arterburn LM. 2007 Docosahexaenoic and arachidonic acid concentrations in human breast milk worldwide. Am J Clin Nutr.;85(6):1457-64.] In women supplemented with DHA at a level of 200-400 mg/day, DHA levels are increased to at least 0.32% of milk fat, and this is a level associated with an enrichment of infant DHA levels. [3.Sherry CL, Oliver JS, Marriage BJ. 2015 Docosahexaenoic acid supplementation in lactating women increases breast milk and plasma docosahexaenoic acid concentrations and alters infant omega 6:3 fatty acid ratio. Prostaglandins Leukot Essent Fatty Acids.;95:63-9.] This level of supplementation should begin during pregnancy and continue throughout lactation.
If breast-feeding is not an option, infant formula supplemented with both DHA and arachidonic acid (AA) is recommended, and many formulae nowadays are supplemented with DHA and AA. Studies have shown that DHA and AA supplementation improves infant levels of these fatty acids. For example, in the DIAMOND study, infants were supplemented for 12 months with varying levels of DHA from 0 to 0.96% of total fatty acids, as well as 0.64% of total fatty acids as AA. DHA levels increased by 0, 149, 204, and 256%, respectively. [4. Birch EE, Carlson SE, Hoffman DR, Fitzgerald-Gustafson KM, Fu VL, Drover JR, Castañeda YS, Minns L, Wheaton DK, Mundy D, Marunycz J, Diersen-Schade DA. 2010 The DIAMOND (DHA Intake and Measurement of Neural Development) Study: a double-masked, randomized controlled clinical trial of the maturation of infant visual acuity as a function of the dietary level of docosahexaenoic acid. Am J Clin Nutr. 2010 Apr;91(4):848-59.] However, the majority of mothers wean their infants at or close to 6 months of age, at which time solid foods are introduced into the infants’ diet.
Although there is somewhat of a carry-over effect of DHA supplementation, such that DHA levels in DHA-supplemented infants remain somewhat higher than in non-supplemented infants for a period of time, by 12-months of age this benefit has disappeared. Birch et al. (1998) illustrated this effect in a study of 108 full-term infants, 79 of whom were exclusively fed DHA- or DHA+AA-supplemented infant formula from birth while 29 were exclusively breast-fed, for a period of 17 weeks, followed by introduction of solid foods. [5. Eileen E Birch, Dennis R Hoffman, Ricardo Uauy David G Birch and Claude Prestidge 1998 Visual Acuity and the Essentiality of Docosahexaenoic Acid and Arachidonic Acid in the Diet of Term Infants Pediatric Research; 44: 201–209.] Although infant levels of DHA in both the supplemented groups and in the breast-fed infants were similarly high at 17 weeks, DHA levels had dropped precipitously by 52 weeks. Table 1 below illustrates this effect.
Table 1 DHA concentration in red blood cell total lipids (µg/mL of packed RBCs) of infants
|Group||17 weeks||52 weeks||% change|
|DHA supplemented formula||92||35||-62%|
|DHA+AA supplemented formula||76||28||-63%|
From 17 weeks, when supplementation ended, to 52 weeks, when infants were on a mixed diet, DHA levels dropped by 62 and 63% in the DHA and DHA+AA groups, respectively. In a follow-up study, Hoffmann et al. (2000) noted the same effect in a similar study of 87 infants, 58 of whom were followed up to 52 weeks. [6. Dennis R. Hoffman, Eileen E. Birch, David G. Birch, Ricardo Uauy, Yolanda S. Castaneda, Maia G. Lapus, and *Dianna H. Wheaton 2000 Impact of Early Dietary Intake and Blood Lipid Composition of Long-Chain Polyunsaturated Fatty Acids on Later Visual Development Journal of Pediatric Gastroenterology and Nutrition; 31:540–553.]
Birch et al. also illustrated the effect, on AA levels, of the shift to a mixed diet in infant feeding. Table 2 represented these results. They illustrate the fact that although DHA levels are decreased following the cessation of DHA supplementation in infants, results for AA levels are mixed. In previously DHA-supplemented infants, AA levels are increased by Week 52, and this reflects the high level of AA in the typical N. American diet, relative to the DHA level. However, in infants supplemented with both DHA and AA, AA levels are decreased by week 52, and this is also true of breast-fed infants. The decrease in AA in these groups of infants reflects the relatively high levels of AA in both breast milk and in DHA+AA-supplemented formula, compared to the AA content of the typical diet they are fed post-weaning.
Table 2 AA concentration in red blood cell total lipids (µg/mL of packed RBCs) of infants
|Group||17 weeks||52 weeks||% change|
|DHA supplemented formula||140||170||+21.4%|
|DHA+AA supplemented formula||195||162||-16.9%|
The precipitous drop in DHA levels, at a time when infants and toddlers are still developing critical elements of brain function, should be of concern to health agencies and regulators, especially given the concomitant rise in AA levels. For optimum health, an ideal balance of omega-6 to omega-3 fatty acids in the body has been calculated as 1:1 to 4:1, but the typical N. American diet results in much higher ratios, from 10:1 to as much as 20:1. [7. Simopoulos AP 2002 The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed. Pharmacother.;56(8):365-79.] Early promotion of a good balance of omega-6 to omega-3 fatty acids may prove beneficial to both children and adults.