Can arachidonic acid be synthesized de novo in the human body?

• A. Yes, it is synthesized easily
• B. No, it must come from essential fatty acids in the diet, with conversion efficiency very low
• C. Only in the brain
• D. Only in the liver

Answer: (B)

Arachidonic acid can be formed from linoleic acid, an essential fatty acid, but the body’s ability to convert it is limited. The conversion uses enzymes that desaturate and elongate fatty acids through several steps (delta-6 desaturase, elongases, then delta-5 desaturase). Because these steps proceed slowly and compete with the omega-3 pathway, the amount of arachidonic acid produced endogenously is small. Therefore, to ensure adequate levels, these essential fatty acids must be obtained from the diet, and preformed arachidonic acid may be needed in some situations. This isn’t something produced easily from scratch in large amounts, and it isn’t limited to a single organ like the brain or liver.