Vitamin B2, also known as riboflavin, is arguably the only vitamin that gives you a visual cue as to its passage through your body. When there is a lot of vitamin B2 in the diet (or in a supplement), your urine turns bright yellow to show you it is there. In fact, the —flavin in riboflavin comes from flavus, the Latin word for yellow.
Vitamin B2, like the other B vitamins, is involved in energy metabolism. It has also recently been found to affect the metabolism of iron in important ways.
The World's Healthiest Foods are generally very rich in vitamin B2. In fact, well over half of the foods profiled on our site contain at least 5% of the Dietary Recommended Intake (DRI) for vitamin B2. We rate five of our foods as excellent sources of vitamin B2. Another 12 foods rate as very good sources, while 21 rate as good sources.
Like all the B vitamins, vitamin B2 plays a key role in energy production. Its role here is complicated—it is important both for the energy-producing electron transport chain and the metabolism of fat molecules into chemically useful energy. Additionally, vitamin B2 plays a role in the chemistry of other nutrients involved in energy production, including folate and vitamin B6.
Vitamin B2 is one of many nutrients required to recycle glutathione, which is one of the most important antioxidants in the human body. (From a chemical standpoint, what B2 does is facilitate the conversion of oxidized glutathione into reduced glutathione.)
We believe that the best protection against free radicals comes from foods that are rich in many different antioxidants. Examples of good vitamin B2 sources that would fit this description include spinach, beet greens, and broccoli, among others.
Marginal vitamin B2 status has been found to impair the ability to make red blood cells, leading to a condition called anemia. There is some debate about how this occurs, with some scientists believing that vitamin B2 is necessary to mobilize iron from storage to incorporate into cells, and others believing that vitamin B2 deficiency impairs iron absorption.
We believe that both of these could be true and recommend making sure your diet contains rich sources of all the nutrients necessary for blood cell production. Here are a couple of examples of recipes—our Baked Chicken Breast with Honey Mustard Sauce and 10-Minute Rosemary Lamb Chopss—that are rich in both iron and vitamin B2.
People eating a standard Western diet receive about one-quarter to one-third of their dietary vitamin B2 from milk and other dairy products. If you look at the chart below, you'll see milk and yogurt represented as good sources of vitamin B2. To this day, dairy is probably the best publicized source of this nutrient.
We would encourage you, though, to explore other sources of vitamin B2. For example, crimini mushrooms are an excellent source of vitamin B2, and many leafy green vegetables also end up as good to excellent sources, as well.
In terms of food groups, we see almost all of them containing foods that are contributors to vitamin B2 nutrition. Many non-dairy animal foods—including turkey, sardines, and eggs—end up in the top third of our B2-rich foods. Legumes—and particularly soy foods—are also well represented.
Many types of vegetables are rich in vitamin B2. In addition to leafy greens, which are rich sources of a wide array of nutrients, we see other Brassica vegetables (including broccoli, cauliflower, and Brussels sprouts), peppers, root vegetables, and squash on the list of vitamin B2-rich foods.
You can even get vitamin B2 in some natural sweeteners like maple syrup , which contains about 6% of the RDA in just one teaspoon. Our Ginger Yogurt with Fruit is quite rich in vitamin B2, providing almost 40% of the RDA.
As an example of how easy it can be to build a daily meal plan that meets your vitamin B2 needs, let's do it with three sample meals. For breakfast, we'll choose Huevos Rancheros. For lunch, we'll whip up a Healthy Chef's Salad with Walnuts and French Dressing. For dinner, we'll choose the Healthy Chicken Caeser Salad. This gives you about one and one-half times the RDA for vitamin B2.
|World's Healthiest Foods ranked as quality sources of|
|Beet Greens||1 cup||38.9||0.42||32||15.0||excellent|
|Mushrooms, Crimini||1 cup||15.8||0.35||27||30.6||excellent|
|Sea Vegetables||1 TBS||10.8||0.14||11||17.9||excellent|
|Eggs||1 each||77.5||0.26||20||4.6||very good|
|Cow's milk||4 oz||74.4||0.21||16||3.9||very good|
|Collard Greens||1 cup||62.7||0.20||15||4.4||very good|
|Broccoli||1 cup||54.6||0.19||15||4.8||very good|
|Swiss Chard||1 cup||35.0||0.15||12||5.9||very good|
|Green Beans||1 cup||43.8||0.12||9||3.8||very good|
|Mushrooms, Shiitake||0.50 cup||40.6||0.12||9||4.1||very good|
|Bok Choy||1 cup||20.4||0.11||8||7.5||very good|
|Turnip Greens||1 cup||28.8||0.10||8||4.8||very good|
|Kale||1 cup||36.4||0.09||7||3.4||very good|
|Mustard Greens||1 cup||36.4||0.09||7||3.4||very good|
|Bell Peppers||1 cup||28.5||0.08||6||3.9||very good|
|Green Peas||1 cup||115.7||0.21||16||2.5||good|
|Sweet Potato||1 cup||180.0||0.21||16||1.6||good|
|Winter Squash||1 cup||75.8||0.14||11||2.6||good|
|Brussels Sprouts||1 cup||56.2||0.12||9||3.0||good|
|Summer Squash||1 cup||36.0||0.07||5||2.7||good|
|Romaine Lettuce||2 cups||16.0||0.06||5||5.2||good|
|Chili Peppers||2 tsp||15.2||0.05||4||4.5||good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%
Arguably, the biggest impact on vitamin B2 nutrition in the food processing chain is due to damage from exposure to light. In fact, one of the reasons your milk is likely to come in a paper carton is to reduce the light damage to the vitamin B2 content.
As light damages the vitamin B2, it produces an off-flavor that makes it taste less fresh. It doesn't take much of this effect to become noticeable. A 10% change occurs over a few days in glass exposed to light and studies show that milk drinkers can taste the difference.
Luckily, the dairy industry has developed methodology throughout the packaging and delivery chain to reduce this problem. You can help retain the most vitamin B2 in your dairy products by purchasing it in opaque containers whenever it will be exposed to light. It's also important to note here that the B2 in cheese, yogurt, and other dairy foods is equally susceptible to damage from light, and those foods need opaque storage containers as well.
Vitamin B2 is surprisingly stable to heat and refrigeration. One recent research group found a negligible loss of vitamin B2 over three days of refrigeration.
Historically, vitamin B2 was believed to be the heat stable fraction of vitamin B. That said, there is some loss of vitamin B2 with prolonged cooking techniques. For example, in one research study, milk boiled for 15 minutes loses 27% of its initial vitamin B2 content.
Like most of the other B vitamins, processing of grains from whole to refined robs them of much of the vitamin B2 content. For example, 60% extraction flour, (the kind most commonly used in ordinary white bread, where 40% of the whole grain is lost during processing), contains only one-fifth of the vitamin B2 content of whole unprocessed wheat. The majority of states in the U.S. require "enrichment" of these highly processed flours with B2 (as well as B1, B3, folic acid, and iron). And manufacturers in all states generally comply with the Food and Drug Administration's voluntary guideline for enrichment of processed flour, which has been around since the 1940's.
In short, then, the best way to ensure good vitamin B2 content of foods is to eat them fresh, keep them (dairy in particular) from prolonged exposure to light, and keep cooking times brief. Following the meal plans on our site you'll be encouraged to do all three.
The risk of deficiency of vitamin B2 in the United States is not very high. It appears that only about 2% of American adults fail to reach the Dietary Reference Intake (DRI) for vitamin B2.
There is an emerging concern about vitamin B2 intake in adolescents, especially adolescent girls. This is the combined result of a reduced intake of dairy products and a well-known aversion to fruits and vegetables in this age group.
We believe that the amount of fresh and varied foods in the World's Healthiest Foods recipe library should ensure that you do not become deficient in vitamin B2.
It is really not difficult to build a diet rich in vitamin B2 using the World's Healthiest Foods. A serving of a soy food—for example, whole soybeans or tempeh—gets you a quarter of the way there. Adding another high-vitamin B2 food such as spinach or yogurt will get you over half a day's supply. From here, a smattering from any of a number of good vitamin B2 sources—and there are many to choose from—should get you to your target.
As noted above, the risk of vitamin B2 deficiency is not very high and usually requires some special circumstances. Aggressive medication protocols for cancer and AIDS have been reported to cause vitamin B2 deficiency. Vitamin B2 deficiency has also been noted in some indigenous populations that eat diets devoid of plant foods.
Vitamin B2 deficiency can impair blood cell production. Although there is some debate about how this happens, it appears that vitamin B2 is necessary to incorporate dietary iron into the forming red blood cell. It has also been hypothesized that deficient vitamin B2 stores impair the absorption of dietary iron.
However this interaction occurs, two separate research groups have shown improvements in blood cell counts through restoring vitamin B2 to the diet in people who had low levels of the vitamin.
As noted above, the stability of vitamin B2 in foods is questionable during storage, particularly if the food is exposed to light. Researchers have recently learned that having other antioxidants in the food, particularly vitamin C, may help to spare the vitamin B2 content.
Vitamin B2 is necessary to convert vitamin B6 to its active form. Hence, deficiency of vitamin B2 could potentially reduce your ability to use vitamin B6, even when there is plenty in your diet.
There are to date no credible reports of toxicity from vitamin B2 that we were able to find. The National Academy of Sciences, similarly unable to demonstrate any health risk, chose not to establish a Tolerable Upper Intake Limit (UL) for vitamin B2 intake.
Since research trials have used doses of supplemental vitamin B2 more than 20 times the Dietary Reference Intake (DRI) without any evidence for adverse effect, we believe it is highly unlikely that you could eat too much vitamin B2 under any circumstance.
One warning, though—vitamin B2 can tend to make the urine appear very yellow. Diets rich in vitamin B2 may induce this effect. It is not considered harmful, but it may appear unusual at first.
In 1998, the Food and Nutrition Board of the National Academy of Sciences (NAS) established a set of Dietary Reference Intakes (DRIs) for vitamin B2 that included Recommended Dietary Intakes (RDAs) by age and gender. Note that the standards for infants under one year of age are Adequate Intake (AI) standards. These are summarized below.
Given the lack of demonstrated toxicity of vitamin B2, the NAS chose not to establish a Tolerable Upper Limit (UL) for vitamin B2 intake.
The Daily Value (DV) for vitamin B2 is 1.7 mg per 2000 calories. This is the value that food labels use as a reference point.
As our WHFoods recommendation for daily intake of vitamin B2, we chose the Dietary Reference Intake (DRI) level for men 14 and older of 1.3 milligrams. (This level is about 20% higher than the DRI for women 19 and older of 1.1 milligrams, and we chose it to make sure that both men and women would be covered by the guideline.)