Every day we interact with objects, places and sensations that affect the way we think and feel. This can be used to the writer's advantage by planting symbols in the reader's path to reinforce a specific message, feeling or idea.
Look at the setting and the character's state of mind, and then think about what you want the reader to see. Is there a descriptive symbol or two that works naturally within the scene to help foreshadow an event or theme, or create insight into the character's emotional plight?
Big, leafy trees
Lush green grass
Fruits and vegetables
Ideal body weight
An apple a day
Caduceus (see picture)
These are just a few examples of things one might associate with health. Some are more powerful than others. Fruits and vegetables are strong symbols, and likely will not require reinforcement. However, a heart could stand for a number of different things and not foreshadow health on its own. Let the story's tone decide if one strong symbol or several smaller ones work the best.