The food system, particularly animal agriculture, is a major contributor to environmental degradation, impacting critical Earth system processes such as climate change, freshwater use, and biodiversity loss. There is a growing consensus that a shift from animal-based to plant-based diets is essential for both human health and environmental sustainability. This review explores the integration of sustainability competences into nutrition education, emphasising how systems thinking, strategic thinking, values thinking, futures thinking, and interpersonal competences can contribute to the production of improved dietary guidelines. By applying these competences to the criticisms of the Planetary Health Diet, the Nordic Nutrition Recommendations, and the Mediterranean diet as examples, this review highlights the tactics used by specific stakeholders to undermine sustainable healthy dietary guidelines. The review paper concludes by advocating for future dietary guidelines that are free of financial conflicts of interest, decolonised, and developed through participatory processes in order to ensure that they are equitable, sustainable, and aligned with the needs of diverse populations.