Actually I've done some tests, food does seem to scale with your level. By how much I couldn't say but the stats I listed in my dat mining appear to be the basics of it. How it probably works is if you eat food under your optimal rank, the stats remain the same (For example, Salt Cod is EVA+5 Ele.Resist+5) and as you progress up in rank past the optimal for that food the bonus likely scales higher to a certain degree. Think of it like the Trump Crown for FFXI, at Lv20 you gain MP+14 HP+14. As your job level scales, the amount of MP and HP the crown grants slowly increases up to a certain amount. Once it reaches that amount (ZAM read the cap as +27 for both HP and MP) you it won't boost your HP or MP values any higher. That's how it's likely for food, the effectiveness of food is based on your rank.
When you're say 10 levels over the optimal rank for that food that's when it caps off on its effectiveness. Eating something closer to your current rank will offer a greater boost than what you had been eating before. SE did this for food in FFXI as well so I wouldn't expect any difference for FFXIV. Just be nice if SE stated how much the boost is for each item so we didn't have to second-guess everything...
EDIT: By the way, the levels and everything above is speculation. In FFXI each type of food item generally had a soft cap that wouldn't go any higher once you reached a certain level.
Edited, Nov 2nd 2010 1:47am by SamusKnight
FINAL FANTASY XIV Roleplayer
Sair Gammonari - Hyur Midlander Male - Conjurer (Somewhat retired.)
Mihana Zhralyia - Miqo'te Seeker of the Sun Female - Archer