Author: Myron Yau, Nutritionist at HKBioTek
Sources of ω-3 fatty acids in Nature
ω-3 fatty acids can be found from a wide variety of plant-based sources since the enzymes for the production of ω-3 fatty acids are only present in plants, and a small number of animal sources when these animals feed on ω-3-fatty-acids-rich plants. The sources are shown as following.
Some plants like flaxseeds, beans and nuts：Algae, Plankton, Flaxseed, Soybean, Walnuts, Chia Seed, Perilla Seed, etc
Deep Sea Fatty Fishes：Salmon, Tuna, Mackerel, Herring, Halibut, Sardines, lake trout, albacore tuna, etc
The ω-3 fatty acids from different sources also imply the type of the fatty acids inside. From the plant sources, the ω-3 fatty acids inside are mainly alpha-linolenic acids (ALA) while Docosahexaenoic Acids (DHA) and Eicosapentaenoic Acids (EPA) inside the animal sources. Human bodies can convert ALA into DHA and EPA but the efficiency is low, less than 10%. In order to obtain sufficient DHA and EPA, sole reliance on plant sources is far from enough.
Health Benefits of ω-3 fatty acids to Humans
The beneficial effects of ω-3 fatty acids to cardiovascular health are well documented. On one side, they compete with ω-6 fatty acids to cause the blood less viscous and lower the LDL-cholesterol in blood, reducing risks of stroke, heart attack and hypercholesterolemia; on the other side, metabolism of ω-3 fatty acids leads to production of weaker inflammation mediators, relieving inflammatory processes and symptoms so as to slow down the initiation step of atherosclerosis.
For infants and children, being a vital constituent of neurological and visual cells, DHA is essential to proper development of their brains and eyes. Although DHA is crucial, whether the supplementations of DHA to term babies’ normal diets are significantly beneficial is controversial. Some trials indicated significantly better social interaction or other cognitive performance in the supplemented groups but a lot more researches did not show any significance difference between supplemented and placebo group, although there is no harm observed in short term.
How much DHA and EPA are enough for optimal health?
For now, scientists cannot answer this question. There is no recommendation for each individual ω-3 fatty acids. For ω-3 fatty acids as a whole, the American Heart Association recommends eating fish (particularly fatty fish) at least two times (two servings) a week. Each serving is 3.5 ounce cooked, or about ¾ cup of flaked fish. Supplementation to term babies is not conclusive in the scientific world. However, for pre-term babies, as their growth and development are not yet completed when delivery, supplementation to their diet with DHA is a more generally recognized as useful.
Excessive ω-3 fatty acids being harmful, the daily upper limit for both adult and children recommended by the Food and Drug Authority in U.S.A is less than 3 grams. Otherwise, excessive bleeding and possible damages to the liver may be resulted.