。
Both study and play are necessary for your health.
Literal
Study [also-も] play [also-も] both health [for-にとって] necessary is.
共に ('both, together') reinforces the parallel inclusion of 勉強 and 遊び — a literary alternative to two も markers. ~にとって is the 'from the viewpoint of X' / 'for X' frame, used when X is the entity for whom something is relevant. The formal copula である closes the statement in essayistic register, fitting the abstract claim about study and play.