From The March 1999 Issue of Nutrition Science News
By Marcia Zimmerman, C.N.
Many health-conscious women who are pregnant or breast-feeding adhere to dietary guidelines set by the American College of Obstetrics and Gynecology
that recommend limiting fat intake for the health of their babies. However, scientists now recognize that specific long-chain polyunsaturated fatty acids (LCPs) are required for the development of a baby's brain, nerves, heart and eyes. Furthermore, research has revealed that pregnant American women do not get enough LCPs in their diet, even when they are not necessarily trying to limit fat intake. [1, 2]This is especially true for vegans and those eating lots of fat-free foods. Vegan diets generally contain plenty of essential fatty acids (EFAs), which are LCP precursors, but not enough are converted into LCPs. Therefore, adopting a low-fat diet without considering the kind of fatty acids eaten will likely not supply enough of the proper LCPs required for
optimal fetal brain development. [3, 4]
Before conception, during pregnancy and the first 12 to 18 weeks after birth are the most critical times for a woman to eat the EFAs her body will ultimately convert into the LCPs her baby cannot yet make on its own.  Women get these dietary EFAs from vegetable, seed and nut oils. EFAs are grouped into two families known as omega-6 and omega-3 fatty acids . Although LCPs from both families are needed for various phases of in utero development, those the mother derives from omega-3 EFAs are often in short supply because of U.S. dietary trends.  Ralph Holman, Ph.D., and colleagues from the University of Minnesota, Minneapolis/St. Paul, theorized that U.S. dietary practices are responsible for the low maternal levels of docosahexaenoic acid (DHA) found in normal American women, both pregnant and nonpregnant.  DHA is an omega-3 fatty acid essential to fetal development and is the end point of the EFA-to-LCP conversion chain.
It takes a long time for the human body to catch up with dietary change. In the past 200 years, we have reduced our intake of marine foods and wild game, which were once plentiful sources of DHA. Since today's diet contains fewer direct dietary sources of DHA, the body must convert omega-3 EFAs to DHA. This has burdened the elongase and delta-desaturase enzymes that must now supply most, if not all, our DHA. Centuries of dietary change have also shifted the balance of our omega-6 and omega-3 fatty acid intake. The hunter-gatherer diet supplied a 1:1 ratio of omega-6s to omega-3s. Today the ratio is estimated to be 20:1 or 30:1 in favor of omega-6s .
In addition, today's livestock is often fed high-omega-6 grains instead of omega-3-rich range grasses, and since animals also need omega-3s to make DHA, this results in animal products containing little, if any, DHA for consumers. Dairy and poultry products that formerly supplied DHA no longer do. Eggs from chickens fed DHA-rich food are becoming available, thus reintroducing an inexpensive source of DHA. Even salmon, normally a good source of omega-3 LCPs, contains lower amounts if the fish have been farm-raised and fed grains rather than phytoplankton, which is their natural food source.
Finally, the growing use of prepared foods has further reduced availability of omega-3s and has increased intake of omega-6s.  With prepared foods has also come increased consumption of saturated and hydrogenated fats, which compound the problem by interfering with enzymatic conversion of EFAs into LCPs. 
Knowing that diet--and fatty acids in particular--has a dramatic effect on fetal development, what can pregnant mothers do to overcome the deficiencies and imbalances prevalent in the typical American diet? According to one expert, "A formula for a healthy brain equals a balance of essential fatty acids."  At no time of life is this more important than during gestation and the neonatal (birth-to-18-week) period. 
Fatty-acid nutrition is crucial to developing full cognitive and visual potential and deterring common conditions such as diabetes, cardiovascular disease, retinitis, poor night vision and dyslexia. [13, 14] Indeed, 70 percent of the total number of brain cells--built to last a lifetime--are developed before a child is born.  During the period of the most rapid fetal and infant growth, which begins at conception and continues until roughly 18 weeks of age, the integral LCPs are the omega-3 DHA and the omega-6 arachidonic acid (AA). These two fatty acids are integrated into fetal and central-nervous-system membranes, including brain, nerves and retina. The heart concentrates these LCPs as well. 
Visual acuity also depends on DHA, which attaches to the outer layers of rod photoreceptors in the retina. Even a marginal DHA deficiency can have long-term effects on visual development. Preterm infants run the greatest risk of vision problems because they miss the final weeks of gestation when the retina concentrates DHA.  Dennis Hoffman, Ph.D., and colleagues from the Retina Foundation of the Southwest, Dallas, proposed DHA be added to infant formulas to improve visual acuity as well as cognitive function. Their research, published in Pediatric Research in 1998, concluded, "Our data and the literature support the benefit of supplementation of both preterm- and full-term-infant formula with DHA (0.35 percent of total fatty acids) either alone or with AA (0.72 percent of total fatty acids)." 
Because of the rapidly growing fetus, a mother's need for LCPs escalates during pregnancy and her own bodily stores are mobilized to provide DHA and AA.  Nonvegetarians have less difficulty supplying AA because they get plenty of omega-6 fatty acids from animal products. Since AA is more readily provided from the mother's diet, most of the recent research has focused on the need for increasing DHA levels during pregnancy and lactation. [20, 21] Scientists have found that maternal DHA levels drop significantly during the course of pregnancy and, although AA levels also drop, they are less likely to remain low. [8, 20] Overall, American women are less able to provide adequate DHA levels during pregnancy and lactation, even compared to women from other countries.  Consequently, U.S.-born babies stand a good chance of having suboptimal DHA levels. [4, 8]
Not surprisingly, premature babies, especially those with the lowest birth weights, are most at risk of DHA deficiency effects. Michael Crawford, Ph.D., from the Institute of Brain Chemistry and Human Nutrition, Hackney Hospital, London, and his colleagues have even suggested that premature birth occurs, in large part, because of maternal DHA deficiency. [8, 9]
David L. Hachey, M.D., from the Baylor College of Medicine, Waco, Texas, also reports that women with low DHA levels may suffer more obstetric complications.  For example, the fatty acid may prevent pregnancy-induced hypertension. Supplementing pregnant women with fish oil, which supplies DHA, reduced this and other obstetric complications and extended gestation time by an average of four days. In addition, full-term babies born to the supplemented mothers were generally healthier and more likely to survive than their counterparts born to nonsupplemented mothers. [4, 8] However, Hachey and others have reported a significant downside to supplementing with fish oils during pregnancy. He noted increased bleeding during delivery among women supplemented with fish oil. A DHA supplement instead of a fish-oil-derived supplement, which contains a blood-thinning fatty acid, alleviates this concern. 
The Benefits of Breast Milk
Ideally, breast milk contains high levels of both DHA and AA to nourish the still-developing infant brain, which is creating new neurons and hundreds of new interneuron connections daily. American women have lower levels of DHA and AA in their breast milk than women from other countries including Japan, several European countries and Nigeria (true only for well-fed Nigerian women). [22, 23] Because the first 12 to 18 weeks of breast-feeding put great demands on maternal DHA stores, those women who have marginal DHA status at delivery have difficulty meeting the needs of their infants. To ensure breast milk contains enough DHA and AA, and to ensure their babies have the best chance at optimal mental function, mothers must eat ample amounts of foods containing these two fats (see table p. 144). Leading researchers have therefore recommended nursing mothers increase their consumption of DHA-rich foods or take a DHA supplement, especially if they do not eat two or three servings of cold-water fish weekly. Even though consuming enough AA appears to be less of a problem--as women are more likely to produce this LCP from their diet--pregnant and nursing mothers should still take note of their AA consumption to ensure they get enough. [24, 25]
There is reason to believe that supplying enough DHA and AA to infants via breast milk makes them smarter. Several investigators have reported a distinct intelligence advantage in babies breast-fed for an average of three or four months compared with babies fed nonsupplemented formula for the same period. DHA supplementation alone also appears to have benefits. When bottle-fed babies were fed formula supplemented with just DHA to match optimal breast-milk levels, researchers observed the same advantages in intelligence scores. Furthermore, the investigators noted that any breast-feeding or supplemented-formula feeding conferred an advantage, but longer periods of time (some studies followed results for 52 weeks) offered additional overall health benefits. [17, 25, 26] Given these findings, what can we do for babies fed standard infant formula?
Leading researchers in the United States argue for adding DHA and AA to infant formula. If U.S. government agencies could be persuaded to mandate adding both these LCPs to infant formula, the greatest beneficiaries might be low-income women who get formula through the Women, Infants and Children agency, and who would otherwise be unlikely to feed their babies supplemented formula. This might go a long way toward increasing the learning and visual abilities, and future success of children from low-income families. 
A number of physicians and nutritionists at New York Hospital-Cornell Medical Center, has formed a group, "Pregnant Physicians for DHA," to educate people about the importance of breast-feeding. In the interests of those who can't breast-feed, they encourage a mandate that DHA be added to infant formula in the United States. 
Adding DHA to infant formulas, although instituted in 50 other countries and approved by the expert panel of the World Health Organization, has not yet been adopted in the United States.  Why is the United States reluctant to add DHA to infant formula? There does not seem to be an obvious reason. The Food and Drug Administration reviewed results of several animal studies investigating potential DHA toxicity. There is currently no evidence of mutagenicity or chromosomal damage at maximum assay doses. Supplemented formulas fed to animals failed to produce any lethal or toxic effects, even at the highest possible doses and for prolonged time periods.  Researchers also failed to find neurotoxic effects or reproductive or developmental abnormalities in test animals at levels in excess of those used in infant formulas. Combined DHA- and AA-enriched formulas have proven highly bioavailable in both animal models and human infants.  DHA and AA, like any other fatty acids, are stored if consumed in excess.
Although we don't know of any downside to DHA-enriched formula, DHA supplements derived from fish oil are not recommended for pregnant women and children
5 years and younger, because fish oil
contains fairly large amounts of EPA and moderate amounts of DHA. In adults, both are assimilated. However, in infants and fetuses EPA might compete with DHA for a place in the nerve cell membranes; therefore, administering fish oil at a young age may be counterproductive. Algae supplements are a better source of DHA for children.
DHA and AA are the predominant LPCs found in breast milk and in infants' brains. Ensuring optimal amounts of these LCPs in pregnant and lactating women and in infant formula can go a long way toward giving the next generation the best chances for health and success. [24, 32]
Marcia Zimmerman, C.N., is founder and CEO of The Zimmerman Group Inc., in Alameda, Calif. Her new book, The ADD Nutrition Solution--A Drug-Free 30-Day Plan (Henry Holt and Co.), will be available in June 1999.
Fatty Acid Metabolism
The ABCs of EFAs
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