In 2018, the FDA began investigating whether the rising popularity of grain-free dog foods had led to a sudden increase in life-threatening heart disease in dogs.

Four years later, the FDA has come to no conclusion, but the publicity surrounding the issue has reduced the once-promising market for grain-free dog foods.

A six-month investigation revealed that a tangled web of funding and industry interests influenced the origin, data collection and conduct of the FDA study.

Grain-free dog food makers and their suppliers have, in turn, lobbied the FDA to protect their market share.