In Chinese you can use "美容的" to describe certain kinds of food that are said to benefit your looks. I've never heard "cosmetic" use to describe food's effects on a person, only the visual appeal of the food itself, so I'm wondering if there is a more appropriate translation.
美容：make oneself more beautiful
美容的食物：beauty foods, beauty-enhancing foods
I even found this:
营养美容: nutritional cosmetology
He said, "The key is having beauty-enhancing foods at hand."
Try the beautifying effect of these common household foods.
Berries: different kinds of berries such as blueberries, blackberries, raspberries, cranberries, as well as strawberries are all super beauty foods.
Our association has an expert to answer questions on all kinds of problems relating to sports massage, acupuncture point massage for common illnesses as well as nutritional cosmetology, health care etcetera.
美容 in 美容食品 is an adjectival noun (beauty) or an adjective (beautifying)
The term 美容食品 (beauty-enhancing food) is relatively new. The traditional term for food that is good for your beauty is 養顔食品.
養顔 can be a verb or an adjective
美容的 in 美容的食品 is an adjective (noun + adjective marker 的) for "beautifying"