Chapter 11: Micronutrients in Metabolism
11.2 Riboflavin (Vitamin B2)
University of Hawai‘i at Mānoa Food Science and Human Nutrition Program
Riboflavin (B2)
Riboflavin is an essential component of flavoproteins, which are coenzymes involved in many metabolic pathways of carbohydrate, lipid, and protein metabolism. Flavoproteins aid in the transfer of electrons in the electron transport chain. Furthermore, the functions of other B-vitamin coenzymes, such as vitamin B6 and folate, are dependent on the actions of flavoproteins. The “flavin” portion of riboflavin gives a bright yellow color to riboflavin, an attribute that helped lead to its discovery as a vitamin. When riboflavin is taken in excess amounts (supplement form) the excess will be excreted through your kidneys and show up in your urine. Although the color may alarm you, it is harmless. There are no adverse effects of high doses of riboflavin from foods or supplements that have been reported.
Riboflavin deficiency, sometimes referred to as ariboflavinosis, is often accompanied by other dietary deficiencies (most notably protein) and can be common in people that suffer from alcoholism. This deficiency will usually also occur in conjunction with deficiencies of other B vitamins because the majority of B vitamins have similar food sources. Its signs and symptoms include dry, scaly skin, cracking of the lips and at the corners of the mouth, sore throat, itchy eyes, and light sensitivity.
Dietary Reference Intakes
The RDAs for different age groups for riboflavin are listed in Table 11.21 “Dietary Reference Intakes for Riboflavin”. There is no UL for riboflavin because no toxicity has been reported when an excess amount has been consumed through foods or supplements.
Table 11.21 Dietary Reference Intakes for Riboflavin[1]
| Age Group | RDA Males and Females mg/day |
| Infants (0–6 months) | 0.3 * |
| Infants (7–12 months) | 0.4* |
| Children (1–3 years) | 0.5 |
| Children (4–8 years) | 0.6 |
| Children (9–13 years) | 0.9 |
| Adolescents (14–18 years) | 1.3 (males), 1.0 (females) |
| Adults (> 19 years) | 1.3 (males), 1.1 (females) |
| Pregnancy | 1.4 |
| Lactation | 1.6 |
| *denotes Adequate Intake | |
Dietary Sources
Riboflavin can be found in a variety of different foods but it is important to remember that it can be destroyed by sunlight. Milk is one of the best sources of riboflavin in the diet and was once delivered and packaged in glass bottles. This packaging has changed to cloudy plastic containers or cardboard to help block the light from destroying the riboflavin in milk. For the riboflavin content of various foods, see Table 11.22 Riboflavin Content of Various Foods”.
Table 11.22 Riboflavin Content of Various Foods[2]
| Food | Serving | Riboflavin (mg) | Percent Daily Value |
| Beef liver | 3 oz. | 2.9 | 171 |
| Breakfast cereals, fortified | 1 serving | 1.7 | 100 |
| Instant oats, fortified | 1 c. | 1.1 | 65 |
| Plain yogurt, fat free | 1 c. | 0.6 | 35 |
| 2% milk | 8 oz. | 0.5 | 29 |
| Beef, tenderloin steak | 3 oz. | 0.4 | 24 |
| Portabella mushrooms, sliced | ½ c. | 0.3 | 18 |
| Almonds, dry roasted | 1 oz. | 0.3 | 18 |
| Egg, scrambled | 1 large | 0.2 | 12 |
| Quinoa | 1 c. | 0.2 | 12 |
| Salmon, canned | 3 oz. | 0.2 | 12 |
| Spinach, raw | 1 c. | 0.1 | 6 |
| Brown rice | ½ c. | 0 | 0 |
- Fact Sheet for Health Professionals, Riboflavin. National Institute of Health, Office of Dietary Supplements. https://ods.od.nih.gov/factsheets/Riboflavin-HealthProfessional/. Updated May 11, 2022. Accessed August 2, 2023. ↵
- Ibid. ↵
A metabolic pathway is a series of chemical reactions that takes a starting molecule and modifies it, step-by-step, through a series of metabolic intermediates, eventually yielding a final product.
Signs refer to readily observed identifying characteristics of a disease such as swelling, weight loss, or fever. Symptoms are the subjective features of a disease recognized by a patient and/or their doctor.
