Depends on the distances and therefore pace you are running in 45mins. Should be around 7 miles assuming you are under 25. Most runners I know do not eat large amounts before setting off, they eat complex carbs (pasta etc) 3-4hrs before as it takes that long to digest them and become available to your blood and increase your glycemic index (available glycogen to muscles). I have read that the glycemic benefit of a high carb meal can remain for 12-16 hrs if not used up by exercise, but shortly before exercise a boost of quick carbs like a jam sandwich (jam for sugar, bread for carbs) can help, eg for footballers help reduce the second half fade. Dextrose and sport bars, gels etc also claim the same, I like the gel as its easily digestible and doesnt "come back" so easily, but the jam sarnie seems to work just as well if you give it 30-45 mins to go down.
Bodybuilders who train their muscles into fatigue eat protein after exercise for "recovery", but I think the important thing for you is stretching and warming down and plenty of water to reduce injuries or their impact.