Vitamin B2, also known as riboflavin, refers to water-soluble B vitamins. Depending on the source, from which it was derived, it was called differently: lactochrome (from milk), hepatoflavin (from liver), ovoflavin (from eggs), verdoflavin (from plants).

Riboflavin structure

The structure of riboflavin consists of two main parts:

  • a heterocyclic molecule consisting of three rings - an isoalloxazine ring,
  • a side chain - D-ribose.

Two words – ribose, a type of sugar, and flavin, meaning yellow, from the Latin flavus, - constitute the term of riboflavin.

Solutions of vitamin B2 have an orange-yellow hue and a yellow-green fluorescence.

Riboflavin taken as supplement adds urine a yellow-orange color.

Vitamin B2 - biological role, health benefits

Riboflavin performs a lot of different physiological functions in the body though its primary role is the releasing of energy from organic molecules.

Vitamin B2 works in a conjunction with flavoproteins as a part of flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) coenzymes. These enzymes (flavoproteins) produce an energy by transferring electrons in a lot of different oxidation-reduction (redox) reactions.

A part of the isoalloxazine ring can give and take hydrogen atoms and their electrons. This ability makes vitamin B2 one of the key players in a synthesis of ATP in mitochondria where it carries hydrogens and electrons from the tricarboxylic acid (TCA) cycle to the electron transport chain.

Oxidation and Reduction FAD

Enzymes containing FMN or FAD catalyze a broad range of biological transformations in both prokaryotic and eukaryotic cells. There are more than 100 enzymes in bacterial and animal organisms which use flavin mononucleotide or flavin adenine dinucleotide.

Flavoproteins take part in two kinds of reactions:

1. Substrates or intermediate metabolites are oxidized by oxygen directly.

In these type of reactions, removing of protons and electrons (dehydrogenation) takes place with a help of different oxidases.

These enzymes are engaged in the oxidation of biogenic amines, aldehydes, an oxidative deamination of amino acids etc.

The product of these transformations can be hydrogen peroxide (H2O2). The creation of hydrogen peroxide is indispensable for an activity of the leukocytes and gives them high germicidal power.

2. The main players of these type of reactions - flavoproteins are engaged in the transportation of protons and electrons from the reduced pyridine coenzymes (NAD).

The enzymes, carrying these reactions, have a leading role in biological oxidation and conversion (tricarboxylic acid cycle, cytochromes, β-oxidation of fatty acids, a transformation of purines, proteins and nucleic acids formation).

Flavoproteins take an essential part in the activation of other vitamins, such as pyridoxine (one form of vitamin B6) and folic acid (Vitamin B9).

In partnership with cytochrome P-450, riboflavin is also engaged in the metabolism (detoxification) of drugs and toxins.

The main functions vitamin B2 in the body include:

  1. regulating the growth and reproduction of cells;
  2. helping to maintain the working state of erythrocytes;
  3. supporting the immune system. It helps mucous membranes, that line the respiratory and digestive systems, to stay in good condition;
  4. supporting phagocytosis, it helps to generate antibodies to fight germs;
  5. playing a significant role in providing of the normal functioning of an eye and protecting the retina from harmful UV rays (riboflavin is a part of visual purple (rhodopsin));
  6. engaging in the normal functioning of the gastrointestinal tract by 1) slightly enhancing the secretory function of the stomach by means of participation in the production of hydrochloric acid; 2) enhancing the secretion of bile; 3) facilitating the assimilation of carbohydrates in the intestines; 4) maintaining optimal microflora; 5) involving in antitoxic and synthetic functions of a liver.

Riboflavin is also engaged in the production of hemoglobin and erythropoietin and promotes insulin secretion. With the help of vitamin C, riboflavin increases glutathione level, one of the most powerful antioxidants in the body. Riboflavin is vital for the absorption and utilization of iron in the body.

Eyes, nerves, skin, nails, hair needs riboflavin to stay healthy. Vitamin B2 might even assist in the preservation of the memory - it is shown that elderly people with high levels of riboflavin were better on memory tests.

The most severe headaches occur during a migraine. A migraine, along with a terrible headache, is followed by nausea, vomiting, and sensitivity to light.

Riboflavin has been studied in connection with its ability to stop migraine headaches.

Modern migraine theory is that migraines are provoked by mitochondrial dysfunction in brain cells. Vitamin B2 assists in maintaining of normal energy creation in mitochondria of a brain, thus reducing or even preventing migraine.

Riboflavin at a high dose of 400 mg per day is recommended for migraine prophylaxis (Sun-Edelstein et al., 2011).

Furthermore, riboflavin acquired new therapeutic interest after it was shown, it can protect the vital tissues from ischemia-induced oxidative damage resulting from heart attack or stroke (Hultquist et al, 1993;. Betz et al, 1994).

Signs and symptoms of riboflavin deficiency

Lack of vitamin B2 may affect the metabolism of vitamin B6, folic acid, niacin, and iron.

True riboflavin deficiency is rare because there are very effective mechanisms for the conservation and re-use of riboflavin in deficiency. Most people get enough riboflavin when eating. In the event of a deficiency, symptoms are frequently correlated with a lack of all B vitamins. That is, all the B vitamins are needed for riboflavin to work well, and vice versa.

Typically, vitamin B2 deficiency manifests itself as problems with the mucous membranes, skin, eyes and blood. The main metabolic effects of riboflavin deficiency are on lipid metabolism.

As riboflavin level drops, people may start to show the slight signs of deficiency in just a few weeks. Initially, they will begin to suffer from a lack of energy and the appearance of insomnia, the eyes start to tire quickly and become more sensitive to light.

Riboflavin deficiency (also called ariboflavinosis) generates inflammation of the membranes and leads to a development of stomatitis. Symptoms of ariboflavinosis include painful red tongue with a sore throat, cracked lips (cheilosis) and inflammation at the corners of the mouth.

Some people are particularly at risk of riboflavin deficiency:

• Athletes.
• Diabetics. Riboflavin can be lost in the urine.
• Pregnant and breastfeeding women.
• Elderly people. About a third of all old people have a riboflavin deficiency, primarily due to poor assimilation, or poor nutrition.
• People who can not digest milk. Dairy products such as cottage cheese are great sources of riboflavin.
• People who take tricyclic antidepressants. Medications, such as amitriptyline, can interfere with riboflavin.

You internalize only about 15 percent of riboflavin from supplements, especially if you take them on an empty stomach. To get the maximum benefit, it is necessary to take supplements with food.

The Top Signs of a Vitamin B2 Deficiency

The recommended daily intake of vitamin B2

RDA for adults is 1.3 mg / day for men and 1.1 mg / day for women.

Epidemiological studies of cataract prevalence indicate that consumption of riboflavin from 1.6 to 2.2 mg per day may lower the risk of developing age-related cataracts. It was shown that elderly people, going through the acute ischemic stroke, had a deficiency of vitamin B2. It was also found that riboflavin deficiency has been bound with a higher risk of fractures in postmenopausal women.

Persons whose diets may not supply ample amounts of riboflavin, particularly those who are older than 50 years, should consider taking a multivitamin to ensure that they have at least 1.7 mg of riboflavin per day.

Table of recommended daily allowance (RDA) of vitamin B2 intake in mg

Age (yr) Infants Children Males Females Pregnancy Lactation
0 - 0.5 0.5 - 1 1 - 3 4 - 8 9 - 13 >14 9 - 13 14 - 18 >19
RDA, mg  0.3  0.4  0.5  0.6  0.9  1.3  0.9  1.0 1.1   1.4  1.6

The optimal dose - 5-20 mg.

Food sources of vitamin B2

The greatest quantity of riboflavin arrives from milk and milk products.

Products such as meat, especially beef liver and oily fish are also excellent sources of vitamin B2. Green vegetables, such as broccoli and brussels sprouts, mushrooms, nuts, eggs, soybeans, whole grains, and nutritional yeast are other good suppliers of riboflavin. Vegans and those who do not consume milk should rely on the intake of large servings of dark green vegetables and cereals which are fortified with riboflavin.

In general, the riboflavin in animal products frequently has a higher bioavailability than in vegetable products.

Partly, the synthesis of vitamin B2 occurs by bacteria in the lower intestine.

Ultraviolet light and radiation destroy riboflavin. In contrast, riboflavin is stable to heat, so the cooking does not reduce vitamin B2 amount in products. In this regard, it is desirable to always store food, such as milk, pasta, grains, and vegetables in opaque containers or a dark place. Eating sun-dried fruits and vegetables, you should know that sunlight broke riboflavin.

The photodegradation of riboflavin can be enhanced by sodium bicarbonate, which is used to preserve the color of vegetables. Furthermore, because riboflavin dissolves in water, it seeps into the water used in cooking. In crops, riboflavin is mainly located in the germ and bran, and removing them from the grain leads to significant its losses.

Safe doses of riboflavin

Toxic or adverse effects of high consumption of riboflavin are known in humans.

If you wish to receive more information about vitamins and their contents in a variety of products, follow the links on the References page.

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