Vitamin B2 (Riboflavin): Reference and Dietary Sources

Abstract

In this article, we describe:

  • the major purposes of this specific nutrient in the human body, 
  • its experimentally confirmed health uses, 
  • conventional ways to estimate nutrient status,
  • nutrient’s toxicities and deficiencies,
  • experimentally confirmed and approved levels of the nutrient intake for different demographics,
  • dietary sources of the nutrient.

Introduction

Riboflavin (also known as vitamin B2) is one of the B vitamins. Riboflavin is naturally present in some foods, added to some food products, and available as a dietary supplement. This vitamin is an essential component of two major coenzymes, flavin mononucleotide (FMN; also known as riboflavin-5’-phosphate) and flavin adenine dinucleotide (FAD). These coenzymes play major roles in energy production; cellular function, growth, and development; and metabolism of fats, drugs, and steroids.

B Complex vitamins are all water soluble and are not stored very well in the body. Thus, they are needed daily through diet or supplement to support their many functions. Deficiencies of one or more of the B vitamins may occur fairly easily, especially during times of fasting or dieting for weight loss or with diets that include substantial amounts of refined and processed food, sugar, or alcohol.

B complex vitamins are fairly easily digested from food or supplements and then absorbed into the blood, mainly from the small intestine. When the amount of Bs taken exceeds the body’s needs, the excess is easily excreted in the urine, giving it a dark yellow color. 

Riboflavin status is not routinely measured in healthy people. A stable and sensitive measure of riboflavin deficiency is the erythrocyte glutathione reductase activity coefficient (EGRAC), which is based on the ratio between this enzyme’s in vitro activity in the presence of FAD to that without added FAD. An EGRAC of 1.2 or less is usually used to indicate adequate riboflavin status, 1.2–1.4 to indicate marginal deficiency, and greater than 1.4 to indicate riboflavin deficiency. However, a higher EGRAC does not necessarily correlate with degree of riboflavin deficiency.

Another widely used measure of riboflavin status is fluorometric measurement of urinary excretion over 24 hours (expressed as total amount of riboflavin excreted or in relation to the amount of creatinine excreted). Because the body can store only small amounts of riboflavin, urinary excretion reflects dietary intake until tissues are saturated. Total riboflavin excretion in healthy, riboflavin-replete adults is at least 120 mcg/day; a rate of less than 40 mcg/day indicates deficiency. This technique is less accurate for reflecting long-term riboflavin status than EGRAC . Also, urinary excretion levels can decrease with age and increase with exposure to stress and certain drugs, and the amount excreted strongly reflects recent intake.

Riboflavin deficiency is extremely rare. In addition to inadequate intake, causes of riboflavin deficiency can include endocrine abnormalities (such as thyroid hormone insufficiency) and some diseases. Certain population groups, such as vegetarian athletes; vegans; pregnant and lactating women and their infants; people with infantile Brown-Vialetto-Van Laere syndrome may be at risk because of riboflavin inadequate intake. It is worth mentioning health benefits of riboflavin for migraine sufferers and cancer prevention (though the study data may be controversial). Adverse effects from high riboflavin intakes from foods or supplements (400 mg/day for at least 3 months) have not been reported, but are not deemed impossible.

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Recommended Dietary Allowances (RDAs) for Riboflavin (Vitamin B2) 

AgeMaleFemalePregnancyLactation
Birth to 6 months*0.3 mg0.3 mg  
7–12 months*0.4 mg0.4 mg  
1–3 years0.5 mg0.5 mg  
4–8 years0.6 mg0.6 mg  
9–13 years0.9 mg0.9 mg  
14–18 years1.3 mg1.0 mg1.4 mg1.6 mg
19-50 years1.3 mg1.1 mg1.4 mg1.6 mg
51+ years1.3 mg1.1 mg  

* Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.

Food Sources of Riboflavin

Foods that are particularly rich in riboflavin include eggs, organ meats (kidneys and liver), lean meats, and milk. 

Green vegetables also contain riboflavin. Grains and cereals are fortified with riboflavin in the United States and many other countries. The largest dietary contributors of total riboflavin intake in U.S. men and women are milk and milk drinks, bread and bread products, mixed foods whose main ingredient is meat, ready-to-eat cereals, and mixed foods whose main ingredient is grain. The riboflavin in most foods is in the form of FAD, although the main form in eggs and milk is free riboflavin.

About 95% of riboflavin in the form of FAD or FMN from food is bioavailable up to a maximum of about 27 mg of riboflavin per meal or dose.The bioavailability of free riboflavin is similar to that of FAD and FMN. Because riboflavin is soluble in water, about twice as much riboflavin content is lost in cooking water when foods are boiled as when they are prepared in other ways, such as by steaming or microwaving.

Selected Food Sources of Vitamin B2

FoodMilligrams(mg) per servingPercentDV*
Pan fried beef liver, 3 ounces2.9223
Fortified breakfast cereal, 1 serving1.7100
Fortified instant oats, cooked with water, 1 cup1.185
Plain yogurt, fat free, 1 cup0.646
Milk, 2% fat, 1 cup0.538
Grilled trimmed boneless beef steak, 3 ounces0.431
Cooked clams, 3 ounces0.431
Sliced grilled mushrooms, ½ cup0.323
Dry roasted almonds, 1 ounce0.323
Swiss cheese, 3 ounces0.323
Rotisserie chicken breast, 3 ounces0.215
Whole, scrambled egg,  1 large0.215
Cooked quinoa, 1 cup0.215
Plain bagel, 1 0.215
Pink salmon, canned, 3 ounces0.215
Raw spinach, 1 cup0.18
Apple with skin, 1 large0.18
Canned kidney beans, 1 cup0.18
Cooked macaroni, whole wheat, 1 cup0.18
Whole wheat bread, 1 slice0.18
Atlantic cod, 3 ounces0.18
Toasted sunflower seeds, 1 ounce0.18
Canned tomatoes, ½ cup0.18
Enriched white rice, cooked, ½ cup0.18
Brown rice, cooked, ½ cup00
  • *DV = Daily Value.
  • The DV for Riboflavin is 1.3 mg for adults and children age 4 and older.  
  • Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.

References

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