Putting EFAs in Perspective

Are they really essential or are their roles exaggerated?

Do essential fatty acids really play vital functions in a child's visual and neurological development as some studies suggest? Or are their roles exaggerated?

    Dr. Dennis Martin Bier, professor of pediatrics and member of the Expert Panel on the Assessment of Nutrient Requirements for Infant Formulas of the Life Sciences Research Office (LSRO) in the United States, offered some answers even as he stressed that a child's optimum development is influenced by factors that go "far beyond the presence or absence of any particular nutrient in infant formula."

    What is important, he said, is to remember that "the things that would allow children to develop their full potential deal with general health, good pediatric care, and good parenting skills." Dr. Bier discussed the role of essential fatty acids (EFA) in an infant's brain development during a symposium organized by the Child Neurology Society, Philippines (CNSP).

Twin Essentials

    There are two essential fatty acids (EFA)-linoleic acid and alpha-linolenic acid or ALA-so-called essential because the body cannot produce them. That they have to be obtained from diet.

    From these two EFAs, we derive two important long chain polyunsaturated fatty acids (LCPUFAs). Linoleic and alpha linolenic acids are referred to as precursors because they make by a series of actions in two separate pathways (omega-6 for linoleic acid and omega-3 for ALA) two products-arachidonic acid (AA) and docosahexaenoic acid (DHA). "But the two pathways share the same series of enzymes," Dr. Bier stressed. Omega-6 and omega-3 compete with each other for these enzymes, thus a different concentration of the precursor in one pathway affects the products produced in the other pathway. He said this is "one of the principal reasons why some researchers suggest adding precursors (EFA) in the formula rather than the products (LCPUFAs) to allow the body to decide how much of one product from one pathway it needs and wants to use."

    Previous studies recommended varying levels of infant requirements for essential fatty acids. From 1962-78, the recommendation was one to five percent of the total energy requirement. In 1976, the American Academy of Pediatrics suggested three percent vis-a-vis the Food and Agriculture Organization/World Health Organization recommendation of 2.7 percent. In 1977, FAO/WHO raised its recommendation to three percent. But in 1998, the LSRO raised the requirement to five to ten percent of dietary calories. It also recommended that LA be about 10 to 15 percent and ALA more than 1.5 percent of the fatty acids, and that these fatty acids be in a specific range of ratios to each other to prevent imbalance.

Vital Roles

    Dr. Bier said the high interest in LCPUFAs was triggered by early studies showing that breastfed infants had higher plasma concentration of LCPUFAs and scored higher on standardized neurodevelopmental tests than formula-fed infants. Since breast milk contained LCPUFAs while the older formulas did not, it was postulated that the LCPUFAs in breast milk was responsible for beneficial effect on neurodevelopment.

    But Dr. Bier observed that while this is plausible, it is also "stretching the facts because breast milk contains thousands of substances only two of which are AA and DHA." He said breastfeeding exerts a far more complicated neurodevelopmental action than what's contained in breast milk, like the effects of maternal bonding, which has nothing to do with breast milk composition.

    That doesn't mean, though, that the LCPUFAs are not necessary. The questions, said Dr. Bier, are: Can infants make LCPUFA when given the precursor EFA? Can they make enough? If they can't, do formulas supplemented with EFA permit LCPUFA resynthesis? Or can formulas supplemented with LCPUFA provide enough to improve visual function and neurodevelopment? Will maternal LCPUFA supplementation in those with low dietary EFA be beneficial? And are these safe to be given to pregnant mothers and newborn infants?

    Dr. Bier said answers to these questions are particularly important for the preterm infants because their enzyme systems, which are necessary to make these products, are immature. Preterm infants are also deprived of all or some parts of the third trimester transfer of LCPUFA from the mother to the fetal brain.

    Dr. Bier cited studies that showed term and even preterm infants can synthesize or convert linoleic and alpha-linolenic acids into AA and DHA (Figure 1). "Human infants, even preterms, soon after birth, are capable of converting the precursors into the products," he said.

Benefit Limits

    The effects of preformed DHA and AA supplementation on infant growth remain unclear as the number of positive and negative results have canceled each other out, either showing no effects or normal growth rates whether supplemented or not.

    The results of studies on visual function also vary. Dr. Bier said there are studies showing improvement in visual function among breastfed infants, particularly those small for gestational age. On the other hand, several studies also show that visual function does not improve in infants given human milk compared to infants given unsupplemented formula.

    Dr. Bier singled out one DHA supplementation study in the US involving breastfeeding mothers. The results showed that the plasma DHA levels increased in both mothers and babies after supplementation. The visual function tests, gross motor development and developmental quotients (DQ) at 12 and 30 months showed no significant advantage after DHA supplementation among supplemented and non-supplemented group. The DHA supplemented group even scored less than the placebo group (Figure 2).

    But the clinical significance remains uncertain, Dr. Bier stressed, noting that "within the normal course of doing a variety of developmental tests over time, it is not unrealistic that one group will have a slightly different development quotient than another strictly based on chance." Essentially, he said the results were perfectly within the normal range. "The preformed DHA supplementation did not make super giant, super intelligent babies. The DHA is no magic bullet that causes a dramatic change in intelligence."

    As for formula supplementation for term infants, Dr. Bier said three of six studies showed positive effect on visual function while the rest did not. A metaanalysis by San Giovanni failed to show "any dramatic improvement of visual function," only varying degrees of positive effect at different ages from two to 12 months, whether measured by visual evoked potential or behavioral tests. "I don't think there are enough strong data that will prove DHA supplementation in term infants has done anything dramatic to infant vision. It was transient and gone very early in development," said Dr. Bier.

    Eight studies looked into neurodevelopment; three showed positive effects, five did not, including the largest blind randomized study by Dr. Nancy Auestad. In this study, Dr. Bier noted "there was absolutely no difference in neurodevelopment" between those who received supplemented or unsupplemented formula, and the mean value was within the normal range (Figure 3).

    Studies involving preterm infants noted some positive effects on vision at two to five months of age, but not in the latter half of the first year.

    In the largest US double-blind randomized trial on preterm infants and neurodevelopment, no difference was seen in visual acuity (measured by Teller Cards) except at four months of age in the group that got DHA + AA supplement sourced from egg and fish. At six months, positive effects were seen in the two groups that received supplements sourced from egg-fish and fish-fungal oils. As for cognitive development, there was an improvement in normality preference among infants who got the egg- and fish-sourced DHA+ AA supplement, but none at nine months. The Bayley Mental Development Index showed no differences in any of the groups. Benefits measured by Bayley Psychomotor Development Index, however, were noted for the sub-group of infants who weighed less than 1,250 grams at birth.

    Summing up, Dr. Bier said more data are required to support the need for supplementation of DHA and AA in term infant formulas as the benefits remain debatable. "In preterm infants, supplementation with a proper balance of DHA and AA may not impair growth, may enhance vision transiently, and may improve neurodevelopment, but still we are not that sure," he noted.

    "The benefits are small and do not stand out. But there is some evidence for efficacy taking place and may not be shared by all infants," Dr. Bier concluded. The effectiveness of adding preformed AA and DHA to formula is still doubtful. But the necessity of linoleic and alpha linolenic acid in the body is affirmed.