Riboflavin

Riboflavin is one of the B vitamins (vitamin B2).  The B and C vitamins are the vitamins that dissolve in water.  A healthy person's gut can easily take riboflavin from food and pass it on to the blood for the body to use. The body needs the B vitamins to get energy from food. Without riboflavin and the other B vitamins people's bodies cannot use fats, carbohydrates, and proteins. Light can break down riboflavin molecules into other molecules that the body cannot use.

If anyone eats too much riboflavin, the gut does not take up enough
to make a person sick, but an injection with too much riboflavin can make one sick. The kidneys take riboflavin out of the blood. They put it in the urine to get it out of the body. If there is much riboflavin in the urine, the urine becomes bright,  yellow. Vitamin pills, or a meal with a lot of liver or egg white turns the urine yellow because these foods put so much riboflavin into the blood.

People may get very sick when their food does not have enough riboflavin. Adding extra riboflavin help. Baby foods, breakfast cereals, pasta, sauces, fruit drinks, and foods such as cheese that are made from milk may have extra riboflavin added.  This is called fortification. To make Vitamin B2 for vitamin pills or to add to foods, industrial companies grow special yeasts, other fungi, or bacteria that make a lot of riboflavin.

These foods have a lot of riboflavin:

Milk
cheese
leafy green vegetables
liver
beans, peas and soybeans 
 yeast
 almonds
 asparagus
 bananas
 okra
 chard
 cottage cheese
 yogurt
 meat
 eggs
 fish

 References 

 Other websites 

Category:B vitamins
Category:Flavins
Category:Alcohols