The B Vitamin Series, Vitamin B2

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In the 1920’s, vitamin B2 was hypothesized to be a necessary factor for preventing pellagra. Pellagra is a vitamin deficiency disease which results in decreased NAD production that causes diarrhoea, dementia and dermatitis.

It wasn’t until 1933 when Kuhn and co-workers isolated a fluorescent, crystalline yellow pigment from egg white that showed growth-promoting properties in rats, that they identified vitamin B2 [1]. This was the first step to the discovery of other flavins that had similar properties. A year later, in 1934, Kuhn noticed that the group of flavins were all structured identically and were noted to be chemically indistinguishable. Riboflavin was the name given to this group of compounds, and Kuhn and his associates went on to successfully synthesis pure riboflavin the same year in Heidelberg, southwestern Germany.

What is the prevalence of vitamin B2 deficiency?

Vitamin B2 deficiency is most prevalent in countries that have diets lacking in dairy products. This is common among rural areas, such as in Guatemala, where a positive correlation was found between the irregularity of milk consumption and vitamin B2 status [2]. Even in countries known for high dairy intake, the prevalence of poor riboflavin status is most common among age groups with the least consumption of milk, which tends to be 4-18 years old [3]. A study of 2127 UK schoolchildren showed 59% of 2-6 year old boys and 78% of 7–10 year old boys had low B2 status. However, prevalence of low vitamin B2 in Western countries is the highest among 15-18 year old girls, with a 95% deficiency rate. This incredibly high prevalence of B2 deficiency among young adults is largely related to a lack of milk consumption, with the UK National Diet and Nutrition Survey showing dairy products contribute between 27-51% of total B2 intake, dependent on age.

Vitamin B2 status is also common among pregnant or lactating women, with clinical signs of deficiency most evident in the time period shortly after giving birth [4]. Low vitamin B2 intakes during pregnancy also increase the chance babies are born riboflavin deficient. In addition, the concentration of B2 in breastmilk tends to be highly dependent on the vitamin status of the mother, and therefore supplementation may be necessary for some women with inadequate diets.

Little concern is given to vitamin B2 deficiency for adults in modernised societies, although it is still prevalent. Surveys predict European adults have between a 7-20% deficiency rate, with up to 27% seen in the United States.

What foods contain vitamin B2?

Vitamin B2 can be found in a wide range of food groups. Plant-based sources are cereals, spirulina, soybeans, dulse, passionfruit juice, mushrooms, pasta, spinach, tomatoes and almonds. Grain products naturally have low amounts of vitamin B2, however fortification practices now make breads and cereals very good sources. Fortification refers to the practice of deliberately increasing the content of an essential micronutrient in a food, irrespective of whether the nutrient was originally in the food before processing. Cereals are now responsible for over 20% of total B2 intake in the UK. Animal-based sources are beef, lamb, milk, yoghurt, wild salmon and eggs.

What are the symptoms of vitamin B2 deficiency?

The most common symptoms of deficiency are weakness, throat soreness, dry skin, blurred vision, dermatitis and anaemia. Symptoms of B2 deficiency are similar to that of low iron intakes and anaemia as human studies show a significant interaction between B2 and iron absorption. Vitamin B2 deficiency may also increase the gastrointestinal loss of iron [5]. Less common symptoms are hair loss, anxiety, constipation and abdominal pain. If you notice any of these symptoms it is important to report them to your General Practitioner.

Age Male Female Pregnancy Lactating
Birth to 6 months 0.3 mg 0.3 mg
7-12 months 0.4 mg 0.4 mg
1-3 years 0.5 mg 0.5 mg
4-8 years 0.6 mg 0.6 mg
9-13 years 0.9 mg 0.9 mg
14-18 years 1.3 mg 1.0 mg 1.4 mg 1.6 mg
19-50 years 1.3 mg 1.1 mg 1.4 mg 1.6 mg
51+ years 1.3 mg 1.1 mg

What are the health benefits of vitamin B2?

It is well established that riboflavin participates in a great number of reactions central to human metabolism. B2’s main use is by acting as electron carriers, specifically through its co-factors flavin mononucleotide and flavin adenine dinucleotide, which is an integral part of energy production. B2 ensures the proper function of oxidative phosphorylation which is the metabolic pathway in which cells use enzymes to oxidize nutrients, release energy, and thereby reform ATP [6].

Vitamin B2 is also necessary to produce glutathione and participates in the redox cycle of glutathione. This cycle is key to protecting humans from excessive oxidative damage by producing antioxidant molecules that counter the damage caused by reactive oxygen species in the body [7]. This physiological benefit is shown in studies where riboflavin has been associated with decreased oxidative stress and increased longevity [8].

Vitamin B2’s antioxidant effect has also shown to be beneficial to lens proteins which typically lead to cataracts when they degenerate. A study found those with the highest vitamin B2 intake had a 33-51% reduced chance of developing cataracts in their lifetime [9].

Riboflavin, along with other B vitamins, is also speculated to elevate homocysteine levels. Adequate riboflavin levels stop a gene polymorphism (MTHFR C677T) during the conversion of homocysteine to methionine. This gene variant is linked with a 14-21% increase in an individual’s chance of developing cardiovascular disease, compared to those without this polymorphism. The polymorphism hasalso been linked with hypertension, a major risk factor for stroke.

Vitamin B2 is found mainly in milk, cereals, grains and red meats. It plays a key factor in maintaining high energy levels, producing glutathione, stopping gene polymorphisms and is also an antioxidant. Consuming B2 can reduce chances of developing high blood pressure and cardiovascular disease, and may increase longevity. A lack of vitamin B2 can result in weakness and anaemia, and can even affect the health of infants for those that are pregnant or have recently had a baby.

  1. Ball. GF. (2008). Vitamins: Their Role in the Human Body, John Wiley & Sons
  2. Boisvert. WA et al. (1993). Riboflavin requirement of healthy elderly humans and its relationship to the macronutrient composition of the diet, J Nutr.
  3. Gregory. J et al. (2004). National Diet and Nutrition Survey of young people aged 4–18 years, London: The Stationery Office
  4. Bates. CJ et al. (1981). Riboflavin status in Gambian pregnant and lactating women and its implications for recommended dietary allowances, Am J Clin Nutr
  5. Yates. CA et al. (2001). Riboflavin deficiency: early effects on post weaning development of the duodenum in rats, Br J Nutr.
  6. Rizlin. R. (2012). Riboflavin, Springer Science & Business Media
  7. Armstrong. JS et al. (2002). Role of glutathione depletion and reactive oxygen species generation in apoptotic signaling in a human B lymphoma cell line, Cell Death Differ.
  8. Powers. HJ. (1999). Current knowledge concerning optimum nutritional status of riboflavin, niacin and pyridoxine, Proc Nutr Soc.
  9. Mares-Perlman. JA et al. (1995). Diet and nuclear lens opacities, Am J Epidemiol.

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