Optimal nutrition for infants--both before and after birth--is an area of research that is still unfolding, and in many cases, the research has yielded unexpected results. One nutrient that has emerged as an important influence in both brain and visual development for infants is DHA--otherwise known as docosahexaenoic acid.

DHA, together with its partner EPA (eicosapentaenoic acid), comprise two types of polyunsaturated fatty acids known as omega-3 fatty acids. Recently, the omega-3 fatty acids have received popular attention for their ability to lower triglyceride and cholesterol levels. They have also been credited with reducing blood pressure, preventing blood clots and possessing anti-inflammatory properties.¹ The best sources of omega-3 fatty acids are cold-water fish (such as salmon, mackerel, albacore tuna and sardines) or plant sources, such as flaxseed or pumpkin seed, and dark green vegetables such as kale, chard or collards.²

Infant Development
But DHA is especially critical in infant development. Research has shown that when infants receive reduced amounts of DHA, they have smaller brain development and may also have poorer visual responses to light.

How does an infant get DHA? Before a baby is born, omega-3 fatty acids are transported from the mother's blood to the placenta, where it is used for membrane development in the brain and retina.³ Therefore, the amount of omega-3 fatty acid in the mother's diet is the determining factor in how much DHA the baby will receive. After the baby is born, the primary source of DHA is breast milk.

Numerous studies show that babies who are breast-fed have better brain development than their bottle-fed counterparts. A recent study in the Lancet corroborated these findings.⁴ After analyzing brain tissue of 22 babies who had died in their first 43 weeks, researchers noted significantly higher amounts of DHA in the brains of the breast-fed babies than in formula-fed babies. What significance does this have? Although researchers have yet to clearly define how DHA affects brain functions, including memory and learning, they know DHA is required for the development of the cerebral cortex--the thin, folded layers of the brain's hemispheres that house billions of brain cells.

Although the evidence that DHA is needed for cerebral cortex development is not conclusive, it is also notable that lower levels of this essential fatty acid are associated with neurological dysfunction, which suggests there are irreversible growth patterns that occur in the very early stages of an infant's development. Researcher Michael Crawford noted that about 70 percent of the total number of brain cells to last an individual's lifetime divide before birth. Indeed, the most active period of brain cell division is in the first few weeks of embryonic development, almost before a woman knows she is pregnant.⁵ After the second month, a fetus' brain grows at a tremendously rapid pace, and 70 percent of all energy consumed goes to brain growth. Even after a baby is born, it will still use up to 60 percent of its energy to feed the brain. All this development appears to pay off. In a related area of research, studies have shown that children who were breast-fed score higher on intelligence tests than children fed with formula.⁶

In addition to its important role in brain development, DHA plays a vital function in developing vision sharpness, or acuity. DHA is found in high concentrations in the photoreceptors of the retina and supplies lipids to the retinal membrane. During the first six months of life, a baby's retinocortical system--which enables it to distinguish between light and dark-- matures rapidly. Healthy, full-term infants have shown an average 20 percent improvement each month between the ages of two and seven months.⁷ Later on, this ability to see fine light and dark contrasts will help babies recognize facial features and expressions.⁸ It has been noted that when levels of DHA are too low, abnormal visual functioning and peripheral neuropathy occur. ⁹

Infant Feeding
As research findings continued to affirm the vitally important role of DHA in infant brain and visual development, certain manufacturers of infant formula began adding DHA to formula. Countries such as Belgium, the Netherlands and Japan have led the way, followed only recently by certain U.S. manufacturers.

Until this new practice was instituted, DHA was only available to infants in human breast milk. Although breast milk remains the primary source of DHA, researchers found significant variations in breast milk DHA levels around the world: the lowest concentrations were found in vegan and American mothers, and the highest, not surprisingly, were found in mothers who ate fish on a regular basis.¹⁰

Adults and DHA
Infants being fed DHA-enhanced formula today may very well encounter new forms of the fatty acid later in life. Some areas being explored include:

* DHA and depression: Researchers at the National Institute of Alcohol Abuse and Alcoholism, Rockville, Md., recently published a study that linked the rising rate of depression to an imbalance in the ratio of omega-6 fatty acids (such as arachadonic acid and linoleic acid) to omega-3 fatty acids.¹¹ Originally, the human diet consisted of a balanced 1:1 ratio between these fatty acids; today, it is estimated to be between 10:1 and 25:1.

* DHA and ADHD: An interesting finding concerning fatty acids may shed some light on children with attention deficit hyperactivity disorder (ADHD). Researchers at Purdue University, West Lafayette, Ind., found that boys diagnosed with ADHD had significantly lower levels of omega-3 and omega-6 fatty acids in their blood, compared to children without ADHD. It was also noted that characteristic symptoms of fatty acid deficiency, such as thirst, frequent urination and dry hair and skin were also prevalent in the boys with ADHD.¹²

Scientists are also exploring the effects of DHA on such varied disorders as schizophrenia, multiple sclerosis and even aggression. Such research will help to further clarify the role of DHA and possibly identify its beneficial uses for both children and adults. In the meantime, the role of DHA in infant development proves it is a highly important element in our nutritional arsenal. Including it in infants' diets, whether in formula or breast milk, can result in dramatic developmental improvements.

Michelle Badash has 12 years of experience working at a nutrition research center in Boston. She has written and edited a newsletter about nutrition research and is also a freelance writer.

REFERENCES

1. Pitchford, P. Healing With Whole Foods: Oriental Traditions and Modern Nutrition, Berkeley, Calif.: North Atlantic Books, 1993.

2. Ibid.

3. Carlson, S.E., Connor, W.E., & Wallingford, J.C. "Synopsis: Dietary omega-3 fatty acids and the development of the brain and retina in human infants," NOAA technical memorandum, NMFS-SEFSC-367, NIH meeting on omega-3 fatty acid research, May 12, 1994.

4. Makrides, M., et. al. "Are long-chain polyunsaturated fatty acids essential nutrients in infancy?" Lancet, 345: 1463-68, 1995.

5. Crawford, M. "The role of essential fatty acids in neural development: Implications for perinatal nutrition," Am J Clin Nutr, 57: 703S-710S, 1993.

6. Lucas, A., et. al. "Breast milk and subsequent intelligence quotient in children born preterm," Lancet, 339: 261-64. Feb. 1, 1992.

7. Makrides, M., et. al. "Erythrocyte docosahexaenoic acid correlates with the visual response of healthy, term infants," Pediatr Rsch, 33(4)425-27, 1993.

8. Carlson, S.E., et. al. "Visual-acuity development in healthy preterm infants: Effect of marine-oil supplementation," Am J Clin Nutr, 58: 35-42, 1993.

9. Hoffman, D.R., et. al. "Effects of supplementation with omega-3 long-chain polyunsaturated fatty acids on retinal and cortical development in premature infants," Am J Clin Nutr, 57: 807S-812S, 1993.

10. Carlson, Connor & Wallingford, op cit.

11. Hibbeln, J., & Salem, N. "Dietary polyunsaturated fatty acids and depression: when cholesterol does not satisfy," Am J Clin Nutr, 62: 1-9, 1995.

12. Stevens, L.J., et al. "Essential fatty acid metabolism in boys with attention-deficit hyperactivity disorder," Am J Clin Nutr, 62: 761-68, 1995.