DHA is an omega-3 long chain polyunsaturated fatty acid (n-3 LCPUFA)
containing 22 carbons and 6 carbon to carbon double bonds denoted as 22:6n-
3. It is an n-3 fatty acid because the first carbon to carbon double bond is on the
third carbon from the methyl end of the fatty acid chain: hence the terminology
n minus 3 (n-3) because you need to count backwards from the methyl end.