Does essential fatty acid absorption change with aging?

Linoleic acid, an essential fatty acid, is a prostaglandin precursor. We investigated the maximal capacity of the proximal jejunum and distal ileum to absorb linoleic acid in the unanesthetized rat. Groups of rats 1, 3, 12, and 28 months of age were studied. As the rats aged, their maximal capacity to absorb linoleic acid increased fivefold both in the jejunum and ileum. Since the intestinal wall content of linoleic acid remained relatively constant, age-related changes in mucosal surface area could not account for our observations. A decrease in the unstirred water layer thickness with aging was detected by measuring potential difference changes across the bowel. The total surface area of the unstirred water layer increased some fourfold and its resistance to linoleic acid transfer decreased fivefold with aging. These changes in the dimensions and characteristics of the unstirred water layer with aging may account for the fivefold increase in the maximal capacity of the small bowel to absorb linoleic acid.