I will suggest some, but it´s advisable to be context-wise, there is not a fits-all answer, because words may have a sense in a context and another in a different one.
- Há estudos que comprovam que exercícios físicos fazem bem à saúde.
There are scientific studies (researches) that have shown benefits from (physical exercise) exercising.
Estudos científicos dizem que dormir bem faz bem para a pele.
Studies/trials/scientific works have comproved/proved healthy the effect in the human skin OR the efficacy of sleeping to the skin health.
And the list could go on and on, forever.
Health of people´s skin. (instead of skin health)
I think now it sounds better.