In the past year, consumers bought more than 26 million gallons of Horizon milk supplemented with DHA algal oil.

Peter Whoriskey writes in WashingtonPost.com that, inside a South Carolina factory, in industrial vats that stand five stories high, batches of algae are carefully tended, kept warm and fed corn syrup. There the Schizochytrium algae multiply quickly. The payoff, which comes after processing, is a substance that resembles corn oil. It tastes faintly fishy.

Marketed as a nutritional enhancement, the oil is added to millions of cartons of organic milk from Horizon, one of the nation’s largest organic brands.

Rich in omega-3 fatty acids, the oil allows Horizon to advertise health benefits and charge a higher price. “DHA Omega-3 Supports Brain Health,” according to the Horizon cartons sold in supermarkets throughout the U.S.

What the Horizon milk carton doesn’t advertise is that some of its contents were brewed in closed stainless steel vats of Schizochytrium. This omission avoids any ick reaction from shoppers, but consumer advocates say it also dodges a key question: Is milk supplemented with an oil brewed in a factory really “organic”?

“We do not think that (the oil) belongs in organic foods,” said Charlotte Vallaeys, a senior policy analyst, at Consumer Reports. “When an organic milk carton states it has higher levels of beneficial nutrients, like omega-3 fats, consumers want that to be the result of good farming practices… not from additives made in a factory.”

Exactly what should be considered an “organic” food? A closer look at how the oil winds up in organic milk offers insight into how the U.S. Department of Agriculture determines what foods may be sold with its coveted “USDA Organic” seal, a label that can double a product’s price. At least in part, it’s a lobbying tug-of-war: On one side, many companies, seeking to maximize sales, push the USDA for an expansive definition of “organic.” On the other, consumer groups advocate for a narrower, “purer,” definition.

In deciding to allow the use of the oil and similar additives, USDA officials, at least initially, misread federal regulations. In 2012, five years after the algal oil was introduced into milk, it quietly acknowledged that some federal regulations had been “incorrectly interpreted.” The USDA then maintained the status quo — allowing the use of algal oil, among other things — in order not to “disrupt” the market.

Asked this month about the issue, a USDA spokesman declined to address the confusion saying that current regulations have been “interpreted to allow for the use of…(DHA) algal oil in organic processed products.”

Whatever the legalities, the Horizon milk with the DHA algal oil is popular. In the past year, consumers bought more than 26 million gallons of the milk supplemented with the DHA, according to Horizon, representing 14 percent of all organic milk gallons sold. Retail sales of the milk topped $250 million in the past year, the company said.

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