以下摘錄自American Dietetic Association

http://www.eatright.org/Public/GovernmentAffairs/92_17084.cfm



N-3 fatty acids



Whereas vegetarian diets are generally rich in n-6 fatty acids (especifically linoleic acid), these diets can be low in n-3 fatty acids, resulting in an imbalance that can inhibit production of the physiologically active long chain n-3 fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Diets that do not include fish, eggs, or generous amounts of sea vegetables generally lack direct sources of EPA and DHA. Recently, vegan sources of DHA derived from microalgae have become available as supplements in nongelatin capsules. Algae sources of DHA have been shown to positively affect blood levels of DHA and of EPA through retroconversion (100).



Most studies show vegetarians, and particularly vegans, to have lower blood levels of EPA and DHA than nonvegetarians (101-104). The new Dietary Reference Intakes recommend intakes of 1.6 and 1.1 grams of -linolenic acid per day for men and women, respectively. These are designated as AIs rather than RDAs. These recommendations assume some intake of long-chain n-3 fatty acids and may not be optimal for vegetarians who consume little if any DHA and EPA (35). The Joint World Health Organization/Food Agriculture Organization (WHO/FAO) Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases (105) recommends 5% to 8% of calories from n-6 fatty acids and 1% to 2% of calories from n-3 fatty acids. Based on an energy intake of 2,000 kcal per day, this would suggest a daily intake of 2.2 to 4.4 grams of n-3 fatty acids. Those who do not receive a preformed source of EPA and DHA require increased amounts of n-3 fatty acids. The recommended ratio of n-6 to n-3 fatty acids is in the range of 2:1 to 4:1 (106-109).



It is recommended that vegetarians include good sources of -linolenic acid in their diet (106,110). These would include foods like flaxseed and flaxseed oil (see Table). Those with increased requirements (eg, pregnant and lactating women or those with diseases associated with poor essential fatty acid status) or those at risk for poor conversion (eg, people with diabetes) may benefit from direct sources of long-chain n-3 fatty acids, such as DHA-rich microalgae (100,106,111).