Which foods contain folic acid?

Many foods. In the US, many grain foods are fortified with folate (folic acid). Concentrations are the highest in liver, yeast, spinach, other greens, and nuts.
Legumes, greens &... Folic acid is a synthetic chemical added to "enriched grains" such as breakfast cereals and pasta. Folate (folic acid) is the naturally occurring form and is found in many foods the best sources are legumes (beans, lentils, peas), leafy greens (esp. Dark ones like spinach & kale), asparagus, strawberries, avocado & liver. See http://www.Folicacidnow.Net/foodchart.Html for a detailed list.