the different usage of Health and Healthy [duplicate]

The term health food is a compound noun and refers to foodstuffs such as muesli, etc. Usually, but not necessarily, you will go to a health food shop to buy such items. There is no guarantee (in the UK) that health food is especially good for you, and some health foods, such as muesli bars, may be frowned upon by dietary experts.

Healthy is simply an adjective, so healthy food is food that is generally acknowledged to be good for you, such as fresh fruit and vegetables. The opposite, of course, is junk food.

Cambridge Dictionary: Health food

Collins Dictionary: Health food shop

Healthline: 10 Processed Foods to Avoid