Research by Texas A&M University’s AgriLife Research center found that ground beef from grass-fed cattle had no beneficial effects on cholesterol levels in humans, while ground beef from grain-fed cattle increased HDL cholesterol, increased LDL particle diameters, and decreased insulin.

Researchers studied three groups of cattle, including one group on a pasture diet with a hay supplement until 20 months old, another group fed by conventional feedlot and kept on a corn-based diet with a hay supplement until 16 months of age or USDA Choice status, and a third group that was fed the corn-based diet until reaching USDA Prime status. Researchers then studied a group of 27 men who consumed ground beef patties made from these sets of cattle over a period of 6 weeks.

No negative effects were identified in the men who ate from the pasture-fed cattle, although some positive effects were observed among those who ate from the corn-fed cattle. The ground beef from the USDA Prime cattle increased HDL cholesterol and LDL particle diameter, which are both protective against cardiovascular disease. The Prime ground beef also decreased insulin, suggesting protective effects from type II diabetes as well.