DHA (docosahexaenoic acid, DHA), a docosahexaenoic acid, is an n-3 long-chain unsaturated fatty acid (n-3 LCPUFAs), which is an important component of cell membranes, rich in brain and retina. In vivo DHA can be synthesized through linolenic acid, but the conversion rate is low, and when the body is deficient in DHA will affect cell membrane stability and neurotransmitter transmission. The body needs DHA mainly through dietary intake, the main sources are fat-rich fish, egg yolk, cultivated seaweed and so on. Chinese textbooks and guidelines have not been explicitly recommending DHA supplementation, and there are no relevant guidelines. This year, the Chinese Journal of Reproductive Health has just published an “Expert Consensus on DHA Supplementation for Maternal and Infant Children in China”, which has attracted attention. So, is DHA supplementation beneficial and how beneficial is it? Is dietary supplementation okay? What are the supplementation options? By reading our guidelines and the recommendations of international guidelines, we will try to give you some knowledge from the most concerned points. DHA and fetal neurological and visual development Studies have found that DHA concentrations in brain tissue increase linearly during the critical period of rapid central nervous development in fetuses and infants from mid- to late pregnancy to 2 years of age. DHA also accounts for a large proportion of the retina and increases the plasticity of optic rod cell membrane discs. Therefore, there is a keen interest in studying whether DHA supplementation during pregnancy will benefit fetal neurodevelopment and visual development. Take a look at a 2014 systematic review published in the European Journal of Nutrition in which the authors analyzed six randomized controlled studies, three of which randomized pregnant women who agreed to participate in the study to an oral 10 ml cod liver oil group (study group) and a 10 ml corn oil group (placebo control group), starting at 18 weeks of gestation and continuing orally until 3 months postpartum, and then at 2 days in infancy, 3, 6, 9 months, and Neurological development was assessed at 4 and 7 years of age, and only one neuropsychological assessment (K-ABC) score was found to be higher in the study group than in the control group at 4 years of age. Of course, the findings of several other randomized studies were positive, with one study suggesting a significant increase in infant problem-solving skills and one suggesting that fish oil supplementation (3 or 7 g/day) from 20 weeks until delivery significantly improved vision and hand coordination in infants and toddlers at 2 or 5-3 years of age. Possible factors influencing the conclusions include the nutritional status of the pregnant woman, medication use, different socioeconomic status, and different underlying diseases, also in that the system of evaluating neurodevelopment may be different. Although studies on the benefits of DHA supplementation during pregnancy have yielded mixed findings, with different gestational weeks and amounts of DHA supplementation initiated in the included populations, different unsaturated fatty acids used, and finally different evaluation systems for neurological development, it is certainly not possible to definitively confirm the beneficial effects of supplementation during pregnancy on fetal neurological and visual development. However, due to some encouraging research results, the positive role of DHA in this regard is still supported by various organizations, including the European Food Safety Authority, the Food and Agriculture Organization of the United Nations, and for the first time in China, a consensus was published this year. DHA and preterm birth prevention Studies on the correlation between DHA supplementation and preterm birth have faced the same inconsistency in conclusions as they differ in the type of unsaturated fatty acids used in the study population, the dose, the duration of use, and the underlying nutritional profile. However, more studies have concluded that DHA supplementation may favor longer gestational weeks, increase fetal birth weight, and reduce the rate of preterm birth before 34 weeks. A large sample of multicenter studies (the FOTIP study) generated a lot of enthusiasm after concluding that DHA may be beneficial in reducing preterm birth. a 2006 Cochrane review systematically evaluated six randomized controlled studies that included 2783 pregnant women randomly assigned to a DHA (or precursor) supplementation group and a placebo control/untreated group and found that receiving fish oil treatment group reduced the risk of preterm birth before 34 weeks (RR 0,69, 95% CI 0,49-0,99). A Chinese expert consensus analysis of the evidence also concluded that DHA supplementation during pregnancy can reduce the risk of early preterm birth and moderately promote fetal growth. Other possible benefits and safety of DHA Current evidence suggests that moderate supplementation with DHA is beneficial and safe, and the FAO recommends an upper limit of 1 g/day of DHA for pregnant and lactating women. 2012 China’s Health and Welfare Commission issued the Standard for the Use of Food Fortification, which recommends that DHA from algae and tuna oil can be added to milk powder, but the percentage of total fatty acids should be less than equal to 0.5%. Of course, there is also concern that DHA supplementation may be beneficial in increasing infant resistance, improving allergies, reducing pre-eclampsia, and reducing postpartum depression. You can refer to this table, which includes 12 better meta-analyses and systematic evaluations, from which it seems that DHA supplementation is more valuable for preterm birth prevention before 34 weeks. Food supplementation – Fish Fish is an excellent source of protein and contains omega- 3 fatty acids. A study evaluating the correlation between diet and cardiovascular risk during pregnancy concluded that consumption of foods rich in unsaturated and fatty acids, including fish, whole grains, fruits and organic vegetables, reduces the risk of preterm birth. Of course, there are different views. Some authors suggest that supplementation may be beneficial for people on unsaturated fatty acid deficient diets, such as whole vegetarians. However, it is also important to be aware that almost all fish and shell-fish contain traces of mercury and should be taken in moderation by pregnant and lactating women. In particular, shark, swordfish, king mackerel and tilefish should be avoided. 2004 EPA recommends that pregnant women consume no more than 12 ounces (seven taels) of low-mercury fish and no more than 6 ounces (three taels) of higher-mercury fish per week. If local fish mercury levels are unknown, the American Academy of Pediatrics and the Obstetrics and Gynecology Association (2012) recommend that overall fish intake should not exceed 6 ounces (three taels) per week. Of course there is still disagreement, and some studies suggest that consuming 340g or more of seafood per week may be beneficial in improving pregnancy outcomes (2007, Hibbeln). As to which one to supplement, DHA>AA>ALA>LA may be preferable based on the priority of DHA, alpha-linolenic acid (ALA), arachidonic acid (AA), and linoleic acid (LA) through the placenta. – from European Journal of Nutrition (2014) 5. Chinese DHA expert consensus recommends that “moderate supplementation of DHA is safe; maintaining appropriate DHA levels in the body is beneficial for improving pregnancy outcomes; the daily intake of DHA for pregnant women and lactating mothers is not less than 200 mg, with an upper limit of 1 g/l DHA intake can be enhanced by consuming 2-3 meals per week of fish with more than one meal of fat-rich seafood and 1 egg per day; consumption of fat-rich seafood should also be considered for possible contaminants”