horizon_organicU.S. Senator Bernie Sanders, an Independent from Vermont, is asking the Justice Department to investigate Dean Foods, the parent company of Colorado-based organic firms like WhiteWave Foods-Morningstar, claiming its leverage in the dairy market is preventing farmers from getting a fair price for their milk.

Dean, headquartered in Dallas, is the only dairy that Sanders singled out by name, according to the Denver Business Journal, which quotes Sanders as saying, “We are talking to the attorney general’s office regarding antitrust activity and issues of concentration of ownership among processors and lack of competition.” That prompted a counter-statement from Dean Foods, the nation’s largest organic dairy producer, defending its operations.

Dean’s WhiteWave-Morningstar division is based in Broomfield and is known for soy products such as the Silk brand. Dean is also the parent of Broomfield’s Horizon Organic Dairy. Earlier this month, Dean was criticized by organic foods advocates after introducing a new line of yogurts and milk labeled “natural.”

As the Los Angeles Times points out, the U.S. Department of Agriculture has approved the term “natural” only for organic meat and poultry.