I'm going on a week long hike in Southern Spain. I envisage myself being away from civilisation max 3 days. What kind of food should I take at any one time? There are infrequent farm houses and outbuildings. A friend recommended dates, nuts, sultanas, carrot, cucumber, olives, salt, pepper for food? What do you think?
First, it makes a big difference if you can bring a water filter with you and take advantage of verified sources of water, and by verified sources I mean water that you are 99.5% sure is going to be there when you are. You can't point out a stream on an old map and rely on it, this is your life source we're talking about.
If you want to prepare yourself for a completely self-sustained hike, the often-agreed upon minimum is 4 to 5 liters per day, and that's just for drinking. At 2 pounds per liter, trying to sustain yourself for more than 2 or 3 days without a water source you can filter from starts to sound like a bold endeavor. Especially if you want 6 or more liters per day in order to have a little extra.
Luckily, food is a little easier. If you had to go a couple days without because you didn't pack enough, in all likelihood you would survive even if you weren't happy about it. If you normally consume about 2000 calories per day, pack about that much and a little extra. For me personally this would mean about 4 freeze dried meals ( accounting for the water needed to rehydrate them ) plus a couple of snacks per day. It will of course be easier to bring lightweight and calorie dense foods but for the most part, you can bring whatever kind of food you please.