Nutrition in the First Year of Life

Addition of preformed DHA/AA is required to bring levels to optimum-Dr. Lien

Breast milk contains a significant amount of long chain polyunsaturated fatty acids (LCPUFAs) specifically linoleic acid and alpha linolenic acid and their metabolites arachidonic acid (AA) and docosahexaenoic acid (DHA). These substances are vital in the growth and development of the infant primarily because they are components of the cell membrane-of the brain and blood vessels.

    There is a significant loss of these substances during the last trimester of pregnancy. Premature infants, therefore, are at great risk for conditions resulting from the deficiency of these substances. This is why fortification of milk formula with DHA and AA is essential.

    Prof. Eric Lien, PhD, an authority on infant nutrition, discussed how DHA and AA affect infant growth and development during a scientific symposium organized by Wyeth Philippines. Prof. Lien is vice president for Nutritional Research and Development of Wyeth Nutritionals International. He was a member of the Infant Formula Council, Committee on Nutritional Science and chair of the University of Illinois Nutritional Advisory Committee.

Human Milk

    Prof. Lien stressed that human milk is the ideal model of nutrient composition for infant nutrition. That's why, infant formulas are designed to mimic human milk. Their carbohydrates, fats, and lactose levels are similar. But he noted infant formulas have higher levels of protein "to meet all the essential amino acid requirements of the growing infant." On the other hand, cow's milk is very saturated, has very low levels of essential LCPUFAs, and cannot be used as a base in formulating a milk supplement for the second six months of life.

    Human milk contains high levels of linoleic acid and alpha-linolenic acid and moderate levels of DHA and AA. Prof. Lien presented the results of a survey they conducted to evaluate human milk fatty acid levels. Studying 450 mature human milk samples from nine countries including the Philippines, they noted constant levels of AA, generally falling between 0.3 to 0.5 percent. These levels are not dependent on maternal diet.

    But this was not the case with DHA, as its amount in human milk is influenced by the mother's diet. Prof. Lien noted that in women who do not consume a significant amount of fish or other sources of omega-3 fatty acids, like those in the US, Canada, United Kingdom, and Mexico, DHA levels are modestly low. "It is important to realize that DHA is diet dependent. However, there also appears to be a protection limit for infants and that for DHA is about 0.2 percent," said Prof. Lien.

Role in Tissue Growth

    AA and DHA perform significant roles in tissue growth, particularly on brain development. During the first six months of pregnancy, the fetus' brain grows at a very limited pace and accelerates in the last trimester. For a term infant, this continues during the first year of life, during which substantial brain growth at a rapid rate can be observed, and extends sometimes beyond the first year of life. Prof. Lien said it is during this phase of rapid brain development when AA and DHA are most essential. For premature infants, human milk will provide the AA and DHA needed in this crucial period. Both have also been added to formulas for low birth weight infants.

    Prof. Lien said studies have shown that the DHA level in the brain is higher among breastfed infants compared to formula-fed infants after the fourth month of life, although they appear to be similar in the first three to four months. Hepatic levels of both AA and DHA are lower in formula-fed than in breastfed infants. Thus, addition of preformed DHA and AA is required to bring their levels to the optimum, said Prof. Lien.

LCPUFAs in the Pediatric Diet

    The weaning process is a delicate transition in infant nutrition and extra care should be taken in providing the growing child with the right amounts of nutrients in the weaning diet. Looking at the typical Filipino weaning diet, Prof. Lien gave some basic weaning recommendations. Breast milk for the first six months and either breast milk or milk supplement for the second six months will provide the major fluid part of an infant's diet. Gradually, cereals can be introduced followed by other soft food and vegetables. Limited amounts of meat or eggs can be given at the end of the first year.

    Prof. Lien emphasized the importance of considering the fat content of the weaning diet. "Keep in mind that breast milk is a high fat formula. It contains 50 percent of its calories as fat, which contains AA and DHA," he reiterated. Fruits and vegetables are high in carbohydrates but very low in fat. So during the second six months of life, the infant's caloric consumption from fat decreases and it is only later when high fat foods are introduced that energy from fat returns to more adult levels. With this consideration in mind, the value of breast milk or of supplemented milk formula as a source of LCPUFAs during the weaning period cannot be undermined.

    Prof. Lien observed that from six to twelve months of age, DHA brain accretion amounts to approximately 800mg or 2.7mg of DHA per day. It has been calculated that the rest of the body requires almost as much DHA as the brain does, bringing the total requirement to about 5mg of DHA per day. "However, the body is not perfectly efficient in using these nutrients in tissue building," said Prof. Lien. In addition to accretion, some DHA is oxidized or broken down, then rebuilt but not back to DHA. This brings the total daily DHA requirement to about 10mg.

    Prof. Lien said that if an infant continues to be breastfed three to four times a day, a vast excess of DHA is actually made available to the infant. However, if the infant is not breastfed or is given a formula that is not fortified with these fatty acids, the deficiency becomes apparent.

Outcome Benefits

    LCPUFAs have been observed to influence the development of various systems in a growing child. Their benefits are best appreciated for visual acuity and cognitive development.

    A study by Birch et al. explored the effects of DHA/AA supplementation on the visual outcome in term infants by measuring the visual evoked potential. They noted that infants given either breast milk or supplemented formula have better vision than those who received unsupplemented formula at one year of age. The difference is about one line in the eye chart. This effect carries over to childhood where they observed differences in stereo acuity or the ability to see three-dimensional figures.

    In terms of mental development, Prof. Lien cited a metaanalysis by Dr. Anderson of 11 studies published from 1978 to 1996 showing that breastfeeding was significantly beneficial.

    Another notable study is that of Willatts et al. comparing DHA and AA supplemented vs. unsupplemented milk formula and its effect on a child's performance in a three-step problem-solving model appropriate at eight months of age. The investigators noted a significant difference in the performance of infants on supplemented formula compared with that of infants on unsupplemented formula. The researchers continued to test the infants at older ages and saw significant differences in favor of the supplemented formula group.