Four hundred and twenty-eight infants over a 4-year period were studied for approximately 4,000 patient-months of observation while receiving five different milk mixtures varying in linoleic acid content from less than 0.1 to 7.3% of the calories.

It was found that linoleic acid is a required nutrient for the young human infant.

The following pertinent observations were made.
(1) Evidences of linoleic acid deficiency developed in young infants who received either a diet practically devoid of fat or one providing 42% of the calories as fat but extremely low in linoleic acid (less than 0.1% of the calories).
(2) Manifestations of the deficiency state disappeared promptly when linoleic acid was given as the ester or triglyceride or in a milk mixture providing 1% or more of the calories as linoleic acid.
(3) The most characteristic feature of the deficiency state was dryness of the skin with desquamation, thickening and later intertrigo.
(4) The incidence of bacterial skin infections was the same in the different groups. It was noted that young infants receiving diets very low in linoleic acid seemed to react severely when outbreaks of staphylococcal infection developed in the hospital environment.
(5) Records for rate of growth showed unsatisfactory progress for many of the infants on low linoleic acid intakes, whereas the course of events was satisfactory in almost all of the infants who received 1.3 to 7.3% of the calories as linoleic acid.
(6) Blood serum levels for dienoic acid of 5.6 ± 1.8% of the total fatty acids were indicative of the deficiency state, whereas values of 12.9 ± 2.6% of the total fatty acids represented the minimal normal.
(7) Histologic alterations in the skin of infants on diets low in linoleic acid showed the same characteristics as seen in experimental animals.
(8) Infants given milk mixtures extremely low in linoleic acid had a gradual amelioration of fat deficiency manifestations as well as increasing levels of dienoic acid in the blood serum following the introduction of cereals to their diet.