Table of Contents
(Illustration by GGS Information Services/Thomson Gale.)
Riboflavin has a broad range activities related to the conversion of nutrients into energy, making other vitamins and minerals available to the body, and acting as an antioxidant to remove of free radicals from cells.
Without riboflavin, much of the food people eat could not be converted into energy. To produce energy, the body breaks down carbohydrates (starches and sugars) and fats into smaller units (glucose) that are then “burned” (oxidized) by cells to produce the energy they need to function. Riboflavin does not break down carbohydrates by itself. Instead, it joins with compounds called flavins that control the pathway that produces energy from food. Other vitamins such as B1 also are involved in this process. Riboflavin is especially important in supplying energy to muscles during physical activity and to the heart, which needs a continuous supply of energy.
When the body burns nutrients, free radicals are formed as a waste product of oxidation. Free radicals are highly reactive molecules that can damage cell membranes and DNA (genetic material). The damage that free radicals cause to cells is believed to play a role in the development of certain diseases, especially cancer. Riboflavin is an antioxidant. It binds to certain free radicals to neutralize them and remove them from the body so that they do not cause damage.
Riboflavin also plays a role in the way the body uses vitamin B6, niacin, folic acid, ironm and zinc. It helps convert vitamin B6 into its active form and is a necessary part of the chemical reactions that allow niacin to be used by the body. In the absence of riboflavin, less iron is absorbed from the intestines and the production of hemoglobin, the iron-containing molecule in red blood cells transports oxygen around the body, is depressed.
Normal riboflavin requirements
The United States Institute of Medicine (IOM) of the National Academy of Sciences has developed values called Dietary Reference Intakes (DRIs) for vitamins and minerals. The DRIs consist of three sets of numbers. The Recommended Dietary Allowance (RDA) defines the average daily amount of the nutrient needed to meet the health needs of 97-98% of the population. The Adequate Intake (AI) is an estimate set when there is not enough information to determine an RDA. The Tolerable Upper Intake Level (UL) is the average maximum amount that can be taken daily without risking negative side effects. The DRIs are calculated for children, adult men, adult women, pregnant women, and breastfeeding women.
The IOM has not set RDAs for riboflavin in children under one year old because of incomplete scientific information. Instead, it has set AI levels for this age group. No UL levels have been set for any age group because no negative (toxic) side effects have been found with large doses of riboflavin. RDAs for riboflavin measured in micrograms (mg).
The following are the RDAs and AIs for riboflavin for healthy individuals:
- children birth-6 months: AI 0.3 mg
- children 7-12 months: AI 0.4 mg
- children 1-3 years: RDA 0.5 mg
- children 4-8 years: RDA 0.6 mg
- children 9-13 years: RDA 0.9 mg
- boys 14-18 years: RDA 1.3 mg
- girls 14-18 years: RDA 1.0 mg
- women age 19 and older: RDA 1.1 mg
- men age 19 and older: RDA 1.3 mg
- pregnant women: RDA 1.4 mg
- breastfeeding women: RDA 1.6 mg
Sources of riboflavin
People need a continuous supply of riboflavin from their diet because very little riboflavin is stored in the body; any excess is excreted in urine. Almost all healthy people in the United States get enough riboflavin from their diet and do not need to take a riboflavin supplement. In the United States starting in 1943, riboflavin, along with thiamin and niacin, has been added to flour. Other good sources of riboflavin include brewer's yeast, whole grains, wheat germ, and dark green vegetables. Some breakfast cereals are also fortified with riboflavin.
Exposure to light breaks down riboflavin in foods. For example, milk stored in a clear container and left in sunlight for two hours will lose about half of its riboflavin content. Foods containing riboflavin should be stored in opaque containers to prevent breakdown of the vitamin by light. Consumers should select milk in paper cartons rather than glass bottles. Prolonged soaking or boiling also causes foods to lose riboflavin.
The following list gives the approximate riboflavin content for some common foods:
- spinach, cooked, 1/2 cup: 0.21 mg
- asparagus, cooked, 1/2 cup: 0.11 mg
- broccoli, steamed 1/2 cup: 0.09 mcg
- milk, 2% 1 cup 0.40 mg
- milk, nonfat 1 cup: 0.34 mg
- yogurt, low fat: 1 cup: 0.52 mg
- egg, boiled, 1 large: 0.27 mg
- almonds, roasted, 1 ounce: 0.24 mg
- salmon, broiled, 3 ounces: 0.13 mg
- chicken, light meat, roasted, 3 ounces: 0.10 mg
- chicken, dark meat, roasted, 3 ounces: 0.18 mg
- beef tenderloin, broiled, 4 ounces: 0.35 mg
- tempeh, cooked, 4 ounces 0.4 mg
- bread, whole wheat, 1 slice: 0.07 mg
- bread, white, enriched, 1 slice 0.09 mg
Most healthy people in the United States get enough riboflavin in their diet because riboflavin is added to many common foods such as bread. Although dietary supplements containing large amounts of riboflavin do not appear to cause negative health effects, they also do not appear to improve health or athletic performance. Excess riboflavin is simply removed from the body in urine. Riboflavin deficiency, also called ariboflavinosis, rarely occurs alone. People who are riboflavin deficient usually also have deficiencies of other B vitamins. Those who are more likely to develop riboflavin deficiency include:
- newborns who receive light therapy for jaundice
- people with alcoholism
- people with anorexia nervosa (self starvation)
- people with celiac disease who cannot eat products containing gluten (e.g. wheat flour, bread, pasta)
- people who are lactose intolerant or who do not eat dairy products
- older, low income individuals who eat a poor diet of highly processed foods
Riboflavin appears to be safe in high doses and also safe during pregnancy. Extended use of high-dose riboflavin supplements may cause an imbalance with other water-soluble vitamins, especially vitamin B1.
Certain drugs appear to interfere with riboflavin's role in the chemical pathway that converts sugar to energy. These drugs include chlorpromazine and related anti-psychotic drugs, tricyclic antidepressants, quinacrine, a drug used to prevent malaria, and dox-orubicin (Adriamycin), a drug used in cancer chemotherapy. Long-term use of phenobarbitol seems to increase the rate of destruction of riboflavin by the liver.
No complications are expected from riboflavin use. However, for most people, taking riboflavin as a high-dose dietary supplement does not provide any benefits.
Parents should be aware that the riboflavin stores in newborns treated with light therapy for jaundice are rapidly depleted. Parents of these newborns should discuss the need for a short-term riboflavin supplement with their pediatrician.
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