Answer to Question 1
a
Answer to Question 2
Like thiamin, riboflavin serves as a coenzyme in many reactions, most notably in energy metabolism. Women who are carrying more than one fetus or breastfeeding more than one infant may have increased needs for riboflavin. Individuals who are extremely physically active may also have increased riboflavin needs.
When thiamin is deficient, riboflavin may be lacking too, but its deficiency symptoms, such as cracks at the corners of the mouth and sore throat, may go undetected because those of thiamin are more severe. A diet that remedies riboflavin deficiency invariably contains some thiamin and so clears up both deficiencies. Excesses of riboflavin appear to cause no harm, and no UL has been established.
Unlike thiamin, riboflavin is not evenly distributed among the food groups. The major contributors of riboflavin to people's diets are milk and milk products, followed by enriched breads, cereals, and other grain products. Green vegetables (broccoli, turnip greens, asparagus, and spinach) and meats are also contributors. The riboflavin richness of milk and milk products is a good reason to include these foods in every day's meals. No other commonly eaten food can make such a substantial contribution. People who omit milk and milk products from their diets can substitute generous servings of dark green, leafy vegetables. Among the meats, liver and heart are the richest sources, but all lean meats, as well as eggs, offer some riboflavin.
The liver in this photograph was from a deceased patient with an advanced state of cirrhosis.
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