Study finds no clear safety advantage for grass-fed beef

Jul 20, 2010 (CIDRAP News) – A recent study of a modest sample of US retail beef products found little difference between the levels of bacteria in grass-fed and conventionally raised beef, despite marketing claims that grass-fed beef is safer.

Reporting in Foodborne Pathogens and Disease, researchers said they found no significant differences in total coliform bacteria, Escherichia coli, or Enterococcus species. They also looked at antimicrobial resistance and found mixed evidence, with some signs of increased resistance in bacteria isolated from conventional beef as compared with grass-fed beef.

“Taken together, these data indicate that there are no clear food safety advantages to grass-fed beef products over conventional beef products,” says the report by investigators from Purdue University in Indiana and Zhejiang University in Hangzhou, China.

They write that grass-fed beef products are often marketed as safer than conventional grain-finished beef because of the potential effects of the grass diet on gut microbes. But they suggest that other factors, including where and how beef is processed and whether cattle are fed preventive antimicrobials, may have larger effects on contamination in finished products. Grass-fed cattle are more likely to be processed in small facilities and are less likely to be given preventive antibiotics, the authors say.

In view of these factors, they hypothesized that grass-fed beef would have higher overall contamination rates but that conventional products would carry bacteria with higher levels of antimicrobial resistance.

To test this, they collected and analyzed samples of conventional beef and beef labeled as grass-fed from retail stores in Illinois and Indiana between July 2008 and March 2009. Fifty conventional samples were collected from four outlets, and 50 grass-fed samples were gathered from 10 sources, including retail stores, farm stores, and farmers’ markets. About two thirds of the samples in each set were solid cuts of beef such as steaks, and the rest were ground beef. Read More