Tuna
 

Tinned tuna

With too much red meat in the nutritional firing line of late, this high protein alternative is the perfect packed lunch staple. One tin contains 56% of your recommended daily protein intake (muscle fuel, indeed) as well as plenty of fish oils and the vitamin niacin, which the University of California found helps you maintain levels of healthy HDL cholesterol. Just make sure you pick up the tin labelled spring water, not oil; you'll get more omega-3 in every portion, which is good news for your heart.