A federal judge in California agreed to stay a class action lawsuit over General Mills' use of partially hydrogenated oils (PHOs) until the US Food and Drug Administration decides whether its recent ban on the synthetic ingredient leaves room for its use as an additive in food products.

Plaintiff Troy Backus has alleged General Mills violated state and federal law in its use of PHOs, which contain trans fats. However, in deciding whether the case could progress US District Judge Thelton Henderson ruled that the FDA's upcoming decision on the safety of PHOs was pivotal to the case.

“Whether small amounts of trans fats can lawfully be used as a food additive is a complicated question requiring agency expertise, and one that the FDA will be reviewing before June of 2018,” Henderson said. “The court finds that this question, which is central to Backus’ claims in this case, is therefore properly left to the FDA’s determination under the primary jurisdiction doctrine.”

The FDA had issued a final determination in June, pulling PHOs from its “generally recognised as safe” list and giving manufacturers three years to remove the ingredient from their product.