Awareness of the connection between climate change and animal products has created a strong market for plant-based meat alternatives. However, despite its significant environmental footprint, cheese consumption continues to rise. Consumer research indicates that values-based messages can influence food behaviours through the halo effect. The purpose of this study is to explore whether an ethical claim in one domain (the environment) can cause a halo effect in another ethical domain (animal welfare). Specifically, does being "green" cast a "humane halo"? In an online experiment, we recruited 267 participants and randomly assigned them to read either a pro-environmental, anti-environmental, or ethically neutral vignette about a cheese company. After being asked to rate the dairy on how well it treats its cows -- an issue on which no information had been provided -- participants indicated how frequently they would recommend the cheese be consumed compared to other brands. We observed a significant halo effect in both the pro-environmental and anti-environmental framing conditions, however the negative halo was roughly twice the size of the positive halo. Animal welfare ratings predicted product consumption recommendations, indicating the humane halo acted as a mediator. Exploratory analyses suggested the strength of this mediated relationship was a function of participants' environmental values, but only if they received negative information about environmental practices. The observed positive-negative asymmetry implies different strategies may be effective in crafting messages designed to shift consumers to more sustainable diets.