A fatty acid of exogenous (primarily ruminant) origin. Many "odd" length long chain amino acids are derived from the consumption of dairy fats (milk and meat). Pentadecanoic acid constitutes 1.05% of milk fat and 0.43% of ruminant meat fat. The content of heptadecanoic acid in the subcutaneous adipose tissue of humans appears to be a good biological marker of long-term milk fat intake in free-living individuals in populations with high consumption of dairy products. (PMID 9701185; PMID 11238766)