Learn Spanish (Latin America): Para cuidar el corazón, debes tener una dieta saludable. - To take care of your heart, you must have a healthy diet.

Both express obligation, but debes (from deber) is often used for strong advice, recommendations, or moral obligation, much like saying you should or you must do something for your health. Tienes que is usually for external, stricter rules. Also notice that deber is followed directly by the infinitive verb tener without needing a linking word like que.

The English translation says your heart, but the Spanish says el corazón (the heart). Why not tu corazón?

In Spanish, when talking about body parts, clothing, or personal items, you almost always use the definite article (el, la, los, las) instead of a possessive word like tu (your) or mi (my) if the owner is obvious. Because the sentence says debes (you must), it is already clearly understood that we are talking about your own heart.

Why do we use Para cuidar here instead of Por cuidar?

When you want to express the idea of in order to achieve a goal, you use para followed by an infinitive verb (like cuidar). While por is used for things like causes or exchanges, para points directly to a purpose, goal, or destination.