Vitamin B2: Riboflavin: Shiny and smooth tongue? Cracked bleeding lips and mouth corner?


Vitamin B2 with scientific name Riboflavin is one of the nine water soluble vitamins. Like other water soluble vitamins, it’s not easy to get toxic due to over consumption. Studies have shown that people don’t show toxicity even when consume 20 times the amount of recommended.

1/ Functions of vitamin B2:

Unlike vitamin B1, which has a wide range of functions in major systems, vitamin B2 finds its play ground at cellular level. Because of that, vitamin B2 is required for the activities of other vitamins and other bodily function to occur. For example, vitamin B2 is needed for vitamin B6, folic acid (vitamin B9), and vitamin B12 to be fully activated. Since vitamin B6 plays a role in blood cell formation, vitamin B2 actually is indirectly affecting the blood cell formation.

Unlike vitamin B1 which participates in carbohydrate metabolism, vitamin B2 is present in the metabolism process of all macro nutrients, which are carbohydrates, lipids, and proteins. Because riboflavin plays in all three metabolism processes, vitamin B2 deficiency is going to show its signs and symptoms in many ways, such as dry hair, dry skin, compromised eye vision.

2/ Recommended Daily intake of vitamin B2

  • 0-6 months: 0.3 mg/day
  • 7-12 months: 0.4 mg/day
  • 1-3 years: 0.5 mg/day
  • 4-8 years: 0.6 mg/day
  • 9-13 years: 0.9 mg/day
  • Male from 14 years: 1.3 mg/day
  • Female from 14-18 years: 1 mg/day
  • Female from 19 years: 1.1 mg/day
  • Pregnant women: 1.4 mg/day
  • Lactating women: 1.6 mg/day

3/ Deficiency: Signs and Symptoms

  • Sore throat
  • Swollen/irritated mucous membranes (those in nose and throat)
  • Cracked mouth corner (maybe bleeding)
  • Very smooth tongue, maybe cracked, red and swollen (see photo)
  • Anemia (unrelated to iron level)
  • Depression
  • Oily skin or scaly skin (blood test may show high level of homocysteine)
  • Weakened vision
  • Cataract if left unchecked

4/ Who’s at risk?

  • Anorexia
  • People on restricted diet (low caloric diet for long term)
  • HIV/AIDS patients
  • Cancer patients
  • Picky eaters (those who avoid eating vegetables)

5/ Foods rich in vitamin B2

Usually people who eat a wide range of food should not have problem with vitamin B2 deficiency. If you consume 0.5 kg-1 kg of vegetable/fruit daily, consume 250 mL milk/soy milk, and 250 g of yogurt, 200 g of meat/fish a day, you should get enough vitamin B2 and other key nutrients. Select a variety of the food list below to meet your vitamin B2 recommended intake.

  • Cow’s milk: 250 mL, 0.42 mg vitamin B2
  • Yogurt: 245 g, 0.35 mg
  • Broccoli, cooked: 150 g, 0.2 mg
  • Spinach, cooked: 200 g, 0.45 mg
  • Turnip greens, cooked: 150 g, 0.1 mg
  • cooked beet greens, 150 g, 0.45 mg
  • Carrot cooked or raw: 200 g, 0.12 mg
  • Egg, cooked: 1 large, 0.26 mg
  • Sardines, canned: 100g, 0.22 mg
  • Tuna, cooked: 100 g, 0.14 mg

6/ Vitamin B2 Retention: Avoid sunlight please

The good thing is that vitamin B2 is stable to heat! So, the chance of us getting enough vitamin B2 is higher than that of vitamin B1 as long as we do not leave the food out in the light for days. Direct and indirect sunlight exposure can destroy 10% of vitamin B2 over a few days. Have you ever wonder why these days milk is packaged in paper carton and yogurt is usually in opaque plastic? That effort of the milk industry is to preserve the loss of vitamin B2. Just think about it: if milk or yogurt is exposed to sunlight directly or indirectly over 4 weeks and you can lose 10% of vitamin B2 over 3 days…well it looks like you may lose 50% or more over 1 week, especially when the pasteurization allows the dairy products to last longer.

The first 3 photos show inappropriate packaged dairy products. If these products are stored in these packaging materials and displayed in transparent cooler, you probably don’t get much vitamin B2 from them. I am not saying it’s not worthy since dairy is still a good common source of calcium and protein, but these instances should not be relied on as your source of vitamin B2. Now, if these products have been probably stored to protect them from sunlight exposure, it’s fine. The next 3 pictures show appropriate packaging (the huge jug of milk is packaged in opaque plastic, which is ok.)


dairy products cheese yoghurt milk

dairy products cheese yoghurt milk





Just a quick note: you do not really need to yell at your kids and rush them to finish their milk: an hour or two laying on the counter does not destroy much vitamin B2 (though you may break the food safety code aka time abuse)

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