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Precautions
Riboflavin should not be taken by anyone with a B vitamin allergy or chronic renal disease. Other populations are unlikely to experience any difficulty from taking supplemental B2.
Side effects
Taking supplemental riboflavin causes a harmless intense orange or yellow discoloration of the urine.
Safety
Riboflavin is extremely nontoxic. No cases of toxicity from ingestion of riboflavin have been reported. No toxic or adverse reactions to riboflavin in humans have been identified. A harmless yellow discoloration of urine occurs at high doses. The limited capacity of the gastrointestinal tract to absorb this vitamin makes any significant risk unlikely, and because riboflavin is water-soluble, excess amounts are simply excreted.
Energy cycle
Interest in disorders of homocysteine metabolism has increased since moderate increases in homocysteine have been identified as a risk factor for vascular disease along with rare inborn errors attributable to severe deficiencies of cystathionine-[beta]-synthase, 5-methyltetrahydrofolate/homocysteine methyltransferase, and 5,10-methylenetetrahydrofolate reductase(MTHFR; EC 1.5.1.20). MTHFR is a flavoprotein (riboflavin enzyme) that catalyzes the NADPH-dependent conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. Methyltetrahydrofolate is the most common form of folate in plasma and tissues and serves as the methyl group donor in the 5-methyltetrahydrofolate/homocysteine methyltransferase-catalyzed remethylation of homocysteine to methionine.
Gale Encyclopedia of Alternative Medicine | 2005 | Turner, Judith; Frey, Rebecca | COPYRIGHT 2005 The Gale Group, Inc. (Hide copyright information) Copyright
Riboflavin
Description
Recent research has found that riboflavin is one of three vitamins involved in the regulation of circadian (daily) rhythms in humans and other mammals. Riboflavin helps to activate certain light-sensitive cells in the retina of the eye that synchronize the animal's daily biological rhythms with the solar light/darkness cycle.
Recent studies done at the National Cancer Institute indicate that riboflavin deficiency increases a woman's risk of developing cervical cancer. Further studies of this connection are underway.
Migraine headaches
Some evidence indicates that impaired mitochondrial oxygen metabolism in the brain may play a role in the pathology of migraine headaches. Because riboflavin is the precursor of the two flavocoenzymes (FAD and FMN) required by the flavoproteins of the mitochondrial electron transport chain, supplemental riboflavin has been investigated as a treatment for migraine. A randomized placebo-controlled trial examined the effect of 400 mg of riboflavin/day for three months on migraine prevention in 54 men and women with a history of recurrent migraine headaches. Riboflavin was significantly better than placebo in reducing attack frequency and the number of headache days, though the beneficial effect was most pronounced during the third month of treatment. A more recent study by the same investigators found that treatment with either a medication called a beta-blocker or high-dose riboflavin resulted in clinical improvement, but each therapy appeared to act on a distinct pathological mechanism: beta-blockers on abnormal cortical information processing and riboflavin on decreased brain mitochondrial energy reserve. A small study in 23 patients reported a reduction in median migraine attack frequency after supplementation with 400 mg of riboflavin daily for three months. Although these findings are preliminary, data from most studies to date suggest that riboflavin supplementation might be a useful adjunct to pharmacologic therapy in migraine prevention.
Psychiatric disturbances
Psychiatric disturbances can also be induced by a riboflavin (vitamin B2) deficiency. Six young men were maintained on a riboflavin deficient diet during a riboflavin deficiency study carried out under 24 hour medical supervision - the men were given whole sets of psychological tests during the trial. The young men experienced very significant levels of psychological change as soon as the deficiency started to manifest itself in the body. The young men became depressed and suffered from an increase in lethargy. Some of them complained about suffering from imaginary pains and illnesses - a medical condition called hypochondriasis. When measured on hysteria and psychopathic deviate scales - their scores were all high, and some of them underwent measurable personality shifts that were very significant. However, none of the classic symptoms seen during riboflavin deficiency - including problems like dermatitis and inflammation in the eyes affected the young men before the experiment ended. The men were again supplemented with riboflavin following the period of testing -which lasted about two months - the psychiatric symptoms took longer than two weeks to completely dissipate and the young men were restored to normal.
Carcinogens or cancer causing chemicals found in the human body are also actively detoxified by riboflavin. During one experiment, rats given such carcinogens were spared from developing liver tumors by giving them riboflavin in high doses. At the same time, a deficiency of the vitamin riboflavin can result in the stimulation of the growth of tumors in the body. One example of an increase in utilization and need of riboflavin is show in the fact that less amounts of riboflavin than normal is excreted if a person suffers from cancer of the stomach, breast cancer, uterine cancer, or cancers of the skin and the lungs. This connection between tumors and riboflavin excretion has been demonstrated in one study involving a thousand adults with various cancers, in eighty per cent of such people there was virtually no riboflavin excreted in the urine, notwithstanding the type of tumor they suffered from at the time.
In animals, riboflavin deficiency results in lack of growth, failure to thrive, and eventual death. Experimental riboflavin deficiency in dogs results in growth failure, weakness, ataxia, and inability to stand. The animals collapse, become comatose, and die. During the deficiency state, dermatitis develops together with hair loss. Other signs include corneal opacity, lenticular cataracts, hemorrhagic adrenals, fatty degeneration of the kidney and liver, and inflammation of the mucous membrane of the gastrointestinal tract. Post-mortem studies in rhesus monkeys fed a riboflavin-deficient diet revealed about one-third the normal amount of riboflavin was present in the liver, which is the main storage organ for riboflavin in mammals. About 28 million Americans exhibit a common sub-clinical stage.[10] characterized by a change in biochemical indices (e.g. reduced plasma erythrocyte glutathione reductase levels). Although the effects of long-term subclinical riboflavin deficiency are unknown, in children this deficiency results in reduced growth. Subclinical riboflavin deficiency has also been observed in women taking oral contraceptives, in the elderly, in people with eating disorders, and in disease states such as HIV, inflammatory bowel disease, diabetes and chronic heart disease. The fact that riboflavin deficiency does not immediately lead to gross clinical manifestations indicates that the systemic levels of this essential vitamin are tightly regulated.
9^ a b Brody, Tom (1999). Nutritional Biochemistry. San Diego: Academic Press. ISBN 0-12-134836-9. OCLC 212425693 39699995 51091036 162571066 212425693 39699995 51091036.
10^ Powers J. Hilary. Riboflavin (vitamin B-2) and health, Review Article. Am J Clin Nutr 2003;77:135260
Stability
Because riboflavin is degraded by light, loss may be up to 50% if foods are left out in sunlight or any UV light. Because of this light sensitivity, riboflavin will rapidly disappear from milk kept in glass bottles exposed to the sun or bright daylight (85% within 2 hours).
Riboflavin is stable when heated and so is not easily destroyed in the ordinary processes of cooking, but it will leach into cooking water. The pasteurization process causes milk to lose about 20% of its riboflavin content. Alkalis such as baking soda also destroy riboflavin. Sterilization of foods by irradiation or treatment with ethylene oxide may also cause destruction of riboflavin.
A number of metals and drugs form chelates or complexes with riboflavin and riboflavin-5-phosphate that may affect their bioavailability (30). Among the agents in this category are the metals copper, zinc and iron; the drugs caffeine, theophylline and saccharin; and the vitamins nicotinamide and ascorbic acid; as well as tryptophan and urea. The clinical significance of this binding is not known with certainty in most instances and deserves further study.
30. D.B. McCormick, Riboflavin, in Present Knowledge in Nutrition, 6th ed. (M.L. Brown, ed), International Life Sciences Institute, Washington DC, 1990, p 146.
The Labratory Rat by Mark A. Suckow, Steven H. Veisbroth, Craig L. Franklin
American Colloge of Laboratory Animal Medicine Series, copyright 2006
Because flavoproteins are involved in the activation and tranformation of pyridoxine, folic acid and niacin, and vitamin K, riboflavin deficiency can be observed in conjunction with deficiencies of these vitamins (Rivlin, 1984).
Riboflavin deficiency in rats has been reported to induce eye signs varying in severity from an inflamed condition of the cornea to its complete opacity. The data are conflicting regarding the association between riboflavin deficiency and cataract formation (Bhat, 1982, 1987; Yagi et al., 1989; Dutta et al., 1990). Takemi et al (2004) examined the conjunctiva and cornea of riboflavin-deficient rats. Riboflavin deficiency resulted in a decrease of microvilli and microplicae in the cornea and conjunctiva epithelium. From these findings the investigators concluded riboflavin is essential in the development, maintenance and function of the ocular surface.
Villi morphometry and the kinetics of cell movement on the villi from riboflavin-deficient female Wistar rats were studied. Feeding a riboflavin-deficient diet to weanling rats resulted in a significantly lower number of villi, a significant increase in villus length, and an increased rate of transit of enterocytes along the villi compared to that with the controls (Williams et al., 1995, 1996a). The morphological and cytokinetic changes in duodenums from weanling rats fed a riboflavin-deficient diet for 5 weeks could not be reversed by a 21 day riboflavin-repletion period (Williams et al., 1996b). The earliest point at which riboflavin deficiency affects post-weaning bowel development in rats has been identified to be 96 hours after initiating the deficient diet. The changes affected duodenal crypt cell proliferation and bifurcation with no reduction in villus number (Yates et al., 2001).
Clinical signs of riboflavin deficiency in rats include unthrifty appearance with areas of alopecia on the skin, seborrheic inflammation, cheilosis, angular stomatitis, glossitis, anemia, hyperkeratosis of the epidermis, neuropathy, blepharitis, conjunctivitis, corneal opacity and vascularization, anestrus, and birth defects. (Cooperman and Lopez, 1984; NRC, 1995). The NRC estimated riboflavin requirements for growth and reproduction are 3 and 4 mg./kg diet, respectively (NRC, 1995).