Keep your brain alert by constantly learning and also by eating the right foods. A Mediterranean diet is best for brains, according to a five-year study of 30,000 people in 40 countries. The investigation into how food can affect brain function in middle-aged and the elderly linked diet quality and cognitive decline. It concluded that people on healthy diets were 24 per cent less likely to have diminishing brain function than those eating unhealthily. For better brain health, eat more greens, nuts, fish and olive oil.