Which essential fatty acids must be obtained from the diet?

• A. Linoleic acid (n-6) and alpha-linolenic acid (n-3)
• B. EPA and DHA
• C. Arachidonic acid
• D. Oleic acid

Answer: (A)

Essential fatty acids are fats the body cannot make, so they must come from the diet. Linoleic acid (an omega-6) and alpha-linolenic acid (an omega-3) are those two because humans lack the enzymatic steps to form the first double bonds at the omega-6 and omega-3 positions, so they cannot synthesize them from scratch. The body can convert these short-chain essential fats into longer-chain forms like EPA, DHA, and arachidonic acid, but the conversion is limited, especially for EPA and DHA. That’s why EPA and DHA aren’t considered essential dietary fatty acids, even though they’re important. Oleic acid and arachidonic acid aren’t essential because the body can obtain or synthesize them from the essential fatty acids.