Research from Iowa State University shows that grazing boosts the level of conjugated linoleic acid (CLA) in milk. CLA is a fatty acid thought to help prevent cancer. Milk is one of the main sources of CLA in human diets.

The study involved 12 dairy farms in northeast Iowa and southwest Wisconsin. The researchers collected milk samples from the farms on a monthly basis. Then, they measured CLA as a percentage of the total fatty acids found in the milk samples.

During the study, the average concentration of CLA in milk was 0.35 percent in Iowa and 0.27 percent in Wisconsin. CLA concentrations fluctuated throughout the year. However, the highest levels were observed in the prime grazing months of May and June. For example, in June, milk from two of the farms had average CLA concentrations greater than 1.3 percent.