The Trump administration on Monday proposed a federal rule that would require companies to notify the Food and Drug Administration, or FDA, when introducing a new substance into food products and to explain why they consider it safe. The move marks a partial step toward Health Secretary Robert F. Kennedy Jr.'s promised overhaul of the food system, while again postponing a long-promised definition of ultraprocessed food. Food-safety advocates have long criticized the current process as opaque and say it allows companies to deem ingredients safe without agency approval or public disclosure. Food companies largely avoided a tougher regulatory blow, but trade groups representing snack, beverage and dairy makers said the plan still did not address concerns that new rules could raise food prices.