Essential fatty acids

An essential fatty acid is one that your body needs but cannot assemble from other fats. You have to get it whole, from food. Linoleic acid, found in vegetable oils, is an essential fatty acid. Two others — linolenic acid and arachidonic acid — occupy a somewhat ambiguous position. You can’t make them from scratch, but you can make them if you have enough linoleic acid on hand, so food scientists can work up a good fight about whether linolenic and arachidonic acids are actually “essential.” In practical terms, who cares? Linoleic acid is so widely available in food, you’re unlikely to experience a deficiency of any of the three — linoleic, linolenic, or arachidonic acids — as long as 2 percent of the calories you get each day come from fat.
In 2002, the Institute of Medicine (IOM) published the first daily recommendations for two essential fatty acids, alpha-linolenic acid and linolenic acid. The former is an omega-3 fatty acid (more about that later on in this chapter) that’s found in fish oils, milk, and some veggie oils. The latter is an omega-6 fatty acid (ditto), found in safflower and corn oil. IOM recommends that

• Women get 12 grams linolenic acid and 1.1 grams alpha-linolenic acid per day
• Men get 17 grams linolenic acid and 1.6 grams alpha-linolenic acid per day