Vitamin B2 (riboflavin) is a vitamin required for proper thyroid and adrenal function. It plays a key role in calming the nervous system, dealing with stress and regulating hormones involved with appetite, mood, body temperature, energy and more.

What Does Vitamin B2 Do?

Vitamin B2 Burns Fat

Why is vitamin B2 good for burning fat? That’s because when burning fat your body requires twice as much vitamin B2 than if your body was to burn carbohydrates. When metabolising any substrate for energy, your body uses vitamin B2 which is why it is essential. In fact, all the other B vitamins are also required to metabolise substrates for energy, but none are required at the same level as vitamin B2. This means that in order to lose body fat, you want to consume a good amount of vitamin B2.

Here are a few interesting things to note:

  • When undergoing active weight loss, your body’s requirements for vitamin B2 increase by 60%.
  • If you do cardio for 20 – 50 minutes, 6 times a week, your body’s need for vitamin B2 increases by 60%.

That means your body requires over double the standard amount of vitamin B2 when you’re not losing weight and not doing cardio regularly!

Other Vitamin B2 Functions

As well as playing an essential role in fat metabolism, vitamin B2 has a variety of other essential functions within the body:

Vitamin B2 plays a key role in enzymatic reactions within the body.

Symptoms Of Vitamin B2 Deficiency

You don’t want to be deficient in vitamin B2 because a few of the following symptoms might flare up:

  • Cracked corners of your mouth.
  • Your outer lips become red and crusty.
  • Your tongue and inner mouth become swollen.
  • Skin gets itchy and painful, particularly around your nose, mouth, ears, eyes and genitals.
  • Hands and feet can become unusually sensitive to heat, touch or pain.

Vitamin B2 Requirements

To get an idea of how much vitamin B2 we require, we can look at the recommended daily allowance (RDA). Based on this, men require 1.3 milligrams daily and women require 1.1 milligrams daily. Pregnant or lactating women should aim to get more vitamin B2 and children require less due to having a lower mass.

However, these vitamin B2 requirements are at the low end. Think of them as what is essential to survive. If you want to consume an optimal amount of vitamin B2 for optimum health, I suggest getting 2 – 5 mg vitamin B2 daily. If performing regular cardio or in a state of active weight loss, be aware that vitamin B2 requirements may double. Additionally, high-fat diets may increase this requirement further by 20% – 40% depending on how much fat you consume.

To complicate things even further, there’s a gene known as MTHFR. Those who have a specific variant (or allele) of this gene known as C677T have their needs for vitamin B2 doubled. That’s why I suggest 2 – 5 mg vitamin B2 since that means those consuming 4 mg are effectively only able to use 2 mg of vitamin B2. This ensures they are consuming enough vitamin B2 for their body.

Sources Of Vitamin B2

Fortunately, unlike vitamin A, where food sources are rather sparse and the best source is liver, eggs or milk, vitamin B2 can be acquired from a range of animal and plant foods. Here are the top sources of vitamin B2 divided into 5 tiers based on how much vitamin B2 is present in the foods:

  • Tier 1 provides around 2 – 5 mg per 100g and are great for completely avoiding vitamin B2 deficiency. Unfortunately for most, the only food in this tier is liver. Chicken liver and lamb liver are optimum and a small serving daily will provide enough vitamin B2 for your daily needs.
  • Tier 2 provides about 1 – 2 mg per 100g. Two servings of these foods are required per day to keep vitamin B2 deficiency at bay. The foods in this tier are kidney, heart, spinach and almonds.
  • Tier 3 gives 0.4 – 0.5 mg per 100g. Four to five servings of these foods are needed to prevent deficiency. Foods in this tier include red meat, eggs, salmon, cheese, sesame, mushrooms, seaweed, bran and wheat germ.
  • Tier 4 foods have 0.2 – 0.4 mg vitamin B2 per 100g. Up to ten daily servings of these foods are needed if solely eaten to prevent vitamin B2 deficiency. These foods are most meats which haven’t already been mentioned along with milk and other dairy products.
  • Tier 5 is all the foods that are safe to consume large amounts of as long as they don’t come at the expense of higher tier foods. They have 0.1 – 0.3 mg in high volumes. These foods include grains, nuts, seeds, beans and other vegetables.

Enriched flours and other vitamin B2 fortified foods tend to fall into tier 3 or 4.

Other Causes Of Vitamin B2 Deficiency

Whilst vitamin B2 deficiency can simply be caused by not consuming enough vitamin B2, there are other factors which may cause deficiency:

  • Low stomach acid will decrease protein digestion as stomach acid is required to release vitamin B2 from proteins in food.
  • Excess exposure to sunlight or tanning beds destroys vitamin B2 within you.
  • Exposure of food to sunlight will damage vitamin B2 so don’t leave your food out in the Sun.
  • Alcohol damages your ability to absorb and use riboflavin.
  • Diabetes, stress and trauma may cause more vitamin B2 to be released in urine.
  • Anorexia may cause people to have a low vitamin B2 intake in general.
  • Low thyroid or adrenal hormones make it harder to activate vitamin B2 and cause more to be lost in urine.

Vitamin B2 Supplements

Unlike vitamin A, there is no known level of toxicity for vitamin B2 which means you can take supplements without worrying so much about overdosing on vitamin B2.

Vitamin B2 is not considered a fat-soluble vitamin although it mixes a bit with both water and fat. It’s best absorbed with a meal which contains some fat, so if you decide to take a vitamin B2 supplement, have it with a meal that contains some fat.

Whilst there’s no particular need to take excessively high doses of 50 mg and upwards, there’s no evidence that it’s unsafe to take such large doses.

Just be wary that vitamin B2 supplements may cause your urine to turn yellow. This happens when your body can’t activate vitamin B2 straight away and some of it leaves your body.

Vitamin B2 Summary

So to summarise, let’s go through some key points!

  • Ideally, consume 200g – 400g liver weekly to hit vitamin B2 requirements or eat a few foods from tier 2 and tier 3 categories on a daily basis.
  • If you’re following a high-fat diet (like keto), actively losing weight, performing regular cardio or have the MTHFR gene then your vitamin B2 requirements may be doubled or even tripled.
  • Disease, alcoholism, anorexia, thyroid or adrenal problems all may increase vitamin B2 requirements.
  • If struggling to obtain vitamin B2, consider supplementing with meals containing some fat.

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