近年，因為奧米加-3 (ω-3) 脂肪酸的眾多益處被科學家發現出來，所以愈多公眾留意它們。

ω-3脂肪酸於大自然的來源
ω-3脂肪酸可以於很多植物的食物中找得到，因為製造ω-3脂肪酸所需的酵素只會在植物中找得到；而一小部分的動物會進食含有ω-3脂肪酸的植物，所以亦會含有豐富ω-3脂肪酸。來源包括以下:

植物來源	動物來源
植物如：亞麻籽﹑大豆﹑胡桃﹑奇異籽﹑紫蘇籽，等等	深海脂質魚：三文魚﹑吞拿魚﹑鯖魚﹑ 鯡魚﹑鯛魚﹑沙丁魚﹑灰鱒魚，等等

不同來源中的ω-3脂肪酸亦都暗示出當中的脂肪酸成份。植物中的ω-3脂肪酸主要是α-亞麻酸；而動物中的ω-3脂肪酸主要是二十二碳六烯酸(DHA)和二十碳五烯酸(EPA)。人體可以轉換α-亞麻酸至DHA和EPA，但效率偏低，只有不足一成。如果想吸收足夠的DHA 和EPA，只是依靠植物來源未必足夠。

　　
ω-3脂肪酸對人體的好處
ω-3脂肪酸對心血管健康的正面作用已經清楚地於眾多研究中顯示出來。一方面，它們會與ω-6脂肪酸競爭，降低血液的黏稠度和低密度脂蛋白水平，血液流動變得更流暢，從而減低中風﹑心臟病發作和膽固醇過高的風險；另一方面，ω-3脂肪酸的新陳代謝會生產出較弱的發炎因子，可緩和本身的發炎情況和症狀，從而減慢初期動脈硬化症的發展。

對嬰兒和兒童的腦部和眼睛而言，DHA是其中一種重要的構成元素，對腦部和眼睛的發育至關重要。雖然DHA是極其重要，但是對足月的嬰兒額外補充DHA有否明顯的好處仍然是十分有爭議性的。一些試驗指出對有額外補充DHA的嬰兒會有較好的社交生活或認知表現。不過，有更多的研究顯示有補充額外DHA嬰兒和沒有比較都沒有明顯的分別，但有補充額外DHA的短期都看不到有害。

多少DHA和EPA才是最健康?
到現時為止，科學家都還未解答到這問題，所以還沒有每一種ω-3脂肪酸的建議食用份量。不過，如果就所有ω-3脂肪酸來說，美國心臟學會建議每星期食用最少兩次(兩個食用份量)的脂質魚，每個食用份量為¾杯魚肉碎。現在的科學知識仍未能對足月嬰兒的額外DHA補充有否益處下定論。不過，對早產嬰兒來說，出生時他們於媽媽肚裡的發育仍然未完成，所以額外的DHA補充被大致認為具有益處的。

過量的ω-3脂肪酸可以有害的。因此美國食物及葯物管理局建議，不論成人或兒童，每日都不應攝取超過3克ω-3脂肪酸。要不然，過量的ω-3脂肪酸可能會導致流血過多和傷害肝臟。

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.

Plant Sources	Animal Sources
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.



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