主题：【文摘】孕期饮食与新生儿睡眠有关 -- 西风陶陶

但是不怕胆固醇么？

DHA and Infant Development

I got interested in this topic thanks to a press release from the NIH about a study of some additives to infant formula that "boosted the average intelligence scores" of the test group of infants.

This is a report of a study done on formula-fed infants (whose parents had already chosen formula before being invited to participate in the study). The researchers broke the infants into three groups. One group got formula, one got formula enriched with arachidonic acid (AA), and one group got formula enriched with AA and docasahexaenoic acid (DHA). Both AA and DHA naturally occur in breastmilk, and both are already used to supplement formula in Europe and Asia. They're believed to help in the development of the nervous system. (These substances are among the long-chain fatty acids or "Omega-3" fatty acids that you might have seen mentioned in the press over the years as wonder foods).

The study reports a significant increase in overall intelligence scores, measured by a test called the BSIDII (Bayley Scales of Infant Development, 2nd Edition) at 18 months for infants who got both AA & DHA. (AA alone was not effective). It's important to note here that "significant" is being used in its statistical sense. That is, the chance that the difference in scores between the two groups was due to chance alone is less than 1/2 of 1%. It does *not* mean significant in the sense that the average person would notice a difference between the groups.

Although the press release says the score that increased "measures small children's memory, their ability to solve simple problems, and their language capabilities", reading the original paper shows they didn't detect any difference on the language score.

They also refer to another study using a larger number of infants (this one used about 60), that did *not* show such an increase. The authors of the current study speculate that this might be due to a different version of the test being used or other factors. They're currently doing a followup at 4 years of age to see whether there's any lasting difference between the groups.

The study also notes that the score they saw an increase on does *not* correlate with IQ or school performance later in life.

So, interesting but hardly conclusive. And, of course, if you're feeding breastmilk in the first place your baby is already getting AA and DHA naturally. But you might want to look at this page, which says: "A woman’s blood and breast-milk DHA levels depend on her diet. Dietary sources of DHA include fatty fish, eggs and organ meats. The fewer DHA-rich foods a woman eats, the lower are the levels of DHA in her blood during pregnancy and in her breast-milk during lactation. It is important for women to eat DHA-rich foods before, during and after pregnancy to assure that their babies are delivered optimal levels of this essential fatty acid they need.

"Women should include sufficient DHA in their diets to ensure that their breast-milk contains enough DHA. (Jensen et al, 1992) Eating 4-5 servings of cooked fatty fish weekly probably satisfies this DHA requirement. DHA levels in the breast-milk of U.S. women are among the lowest in the world and typically deliver 1/2 to 2/3 of the minimum DHA recommended for infants by an Expert Committee of the World Health Organization (WHO) and the U.N. Food and Agriculture Organization (FAO)."

An article on Nutrition Science News Online from 1999 rounds up the evidence on DHA, pregnancy, and breastfeeding. They appear to be advocating DHA supplementation for pregnant women, but not from fish oil, as that seems to correlate with increased bleeding at delivery. They're especially worried about diet-conscious mothers: "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. 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."

DHA is not added to infant formula in the USA, and, in fact, the FDA prohibits its addition. An article from the Washington Post examines both the science and politics behind this stance on the part of the FDA. The waters are murky indeed.

It has no bearing on the science, of course, but there is a very pretty picture of DHA on the web.

There is some more information at DHADOC.com, but take it carefully, as they're associated with another site that wants to sell you DHA supplements.

Update 1/1/2003:

A recent article in Pediatrics titled "Maternal Supplementation With Very-Long-Chain n-3 Fatty Acids During Pregnancy and Lactation Augments Children’s IQ at 4 Years of Age" looked at the effects of supplementing the diet of pregnant women with cod-liver oil from week 18 of pregnancy until 3 months after birth. The researchers then tested the children at age 4 for mental development. Though the followup rate in the study wasn't especially good (590 women originally recruited dwindled to 76 4-year-olds who took the tests and had been breastfed through the 3-month mark), the authors found significant results:

"Children who were born to mothers who had taken cod liver oil (n = 48) during pregnancy and lactation scored higher on the Mental Processing Composite of the K-ABC at 4 years of age as compared with children whose mothers had taken corn oil (n = 36; 106.4 [7.4] vs 102.3 [11.3]). The Mental Processing Composite score correlated significantly with head circumference at birth (r = 0.23), but no relation was found with birth weight or gestational length. The children’s mental processing scores at 4 years of age correlated significantly with maternal intake of DHA and eicosapentaenoic acid during pregnancy. In a multiple regression model, maternal intake of DHA during pregnancy was the only variable of statistical significance for the children’s mental processing scores at 4 years of age."

So, moms-to-be, you might want to think about cod-liver oil, or at least keep the consumption of salmon up there for a few months.