Yes,
Lifestyle modification as part of non-pharmacological treatment of heart diseases are known to have significant effect on patient's health.
Nutrition plays a large part in lifestyle modification.
Role of food and nutrition is part of most residency training and essential reading.
There are specific competencies (entrustable professional activities) that cardiologists must attain and demonstrate for certification.
[From the Entrustable Professional Activities for Subspecialists in Cardiovascular Disease:] by the Americal College of Cardiology : 1
The residents must:
Know the principles of nutrition and obesity assessment and management, including the roles of pharmacotherapy and bariatric surgery.
Ref:
https://www.acc.org/education-and-meetings/products-and-resources/competencies/table-5-cardiovascular-disease-prevention-lifelong-learning-competencies
Also, see: https://www.ahajournals.org/doi/full/10.1161/cir.0000000000000563