What is a good source of riboflavin?

Excellent sources of riboflavin include nutritional (brewer's) yeast, nori (a sea vegetable widely known for its use in sushi), crimini mushrooms, and spinach. Very good sources include summer squash, asparagus, chard, shitake mushrooms, green beans, mustard greens, sunflower seeds, broccoli, collard greens, and turnip greens. Among whole grains, the best source is buckwheat.