I think that they need to research more. To me and to others, the smell coming from the freshly watered tomato leaves is uplifting and invigorating.
Use caution not to ingest them without the knowledge that tomato leaves are toxic to the liver.
Another aspect of gardening is heavier breathing of fresh air that has been slightly purified by the garden plants.
Grz, you are right about the soil based organisms. They are very beneficial, which is why it is important for kids to eat dirt. Kids that play in the dirt and as a result, consume it, have fewer allergy and asthma problems.
The truth is that gardening and growing your own food is downright healthy for a lot of reasons other than just reducing cancer.