Eating certain foods together will help you increase nutrient absorption. For example, foods containing vitamin C will boost iron absorption from plant-based foods, so add a squeeze of lemon juice to a spinach or lentil salad. Tomatoes and olive oil are also a strategic pairing, because the oil boosts absorption of the disease-fighting phytonutrient lycopene in tomatoes. Meals containing vitamin D and calcium are a healthy match so eat foods like salmon, egg yolk and tuna with dairy foods, or calcium-fortified alternatives for vegans.