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Riboflavin and Thyroid Health

Published May 28 2018                                                                          

Riboflavin is a water-soluble B vitamin, and is also known as vitamin B2.  Regarding the different B vitamins, if you search the internet you’ll see that there is a lot of information on other B vitamins, such as folate, vitamin B12, and vitamin B6. But all of the B vitamins are important, including vitamin B2, and hopefully you’ll have a greater appreciation for this vitamin after reading this article.

Riboflavin is the precursor of the coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). These coenzymes play major roles in energy production, cellular function, growth, and development, as well as in the metabolism of fats, drugs, and steroids (1) [1]. The conversion of the amino acid tryptophan to niacin (vitamin B3) requires FAD (1) [1]. In addition, the conversion of vitamin B6 to pyridoxal 5’-phosphate needs FMN (1) [1]. Riboflavin also helps to maintain normal levels of homocysteine, an amino acid in the blood (1) [1].

Many reading this are familiar with MTHFR, but if you’re not familiar with this gene then you can read an article I wrote on this topic [2].  Having a genetic polymorphism of the MTHFR gene (especially if you’re homozygous for C677T) can mean that someone has problems breaking down folate.  However, FAD is a cofactor for MTHFR, and as a result, if someone has a riboflavin deficiency then this can interfere with the metabolism of folate.  The point is that many people with an MTHFR C677T defect supplement with folate and vitamin B12, but they don’t realize the importance of vitamin B2.

How Does Riboflavin Relate To Thyroid Health?

Earlier I mentioned that riboflavin is a precursor of FAD and FMN.  And thyroid hormone is important for the conversion of riboflavin into FAD and FMN.  As a result, those with hypothyroidism will have problems with this conversion.

In fact, I learned from the brilliant Dr. Ben Lynch that even if someone doesn’t have an MTHFR defect, if they have hypothyroidism they will still have problems with MTHFR.  Why is this?  Well, I mentioned earlier that FAD is a cofactor for MTHFR, and healthy thyroid hormone levels are necessary for healthy levels of FAD.  Thus, if someone has a riboflavin deficiency, then will also have an FAD deficiency, which in turn can affect MTHFR.

In addition, autoimmune conditions such as Graves’ disease and Hashimoto’s thyroiditis are characterized by proinflammatory cytokines and oxidative stress.  Riboflavin can help to reduce proinflammatory cytokines and oxidative stress (2) [3] (3) [4].  While I think it’s safe to say that most autoimmune conditions aren’t caused by a riboflavin deficiency, having such a deficiency might prevent someone from getting into remission.

How does riboflavin help to decrease proinflammatory cytokines and oxidative stress?  I’ve discussed glutathione in other articles, and this is considered to be the master antioxidant.  Glutathione reductase is dependent on FAD, and so if someone has reduced riboflavin, this will lead to lower amounts of FAD, which in turn will lead to diminished glutathione reductase acitivity (4) [5].  This in turn will lead to lower glutathione levels.

What Other Conditions Are Commonly Associated With A Riboflavin Deficiency?

Let’s take a look at some of the other conditions that can be related to a deficiency of riboflavin:

Migraines.  One systematic review looked at the role of riboflavin in the treatment of migraines.  The authors concluded that riboflavin is well tolerated, and has demonstrated to be effective in the reduced frequency of migraines (5) [6].  While there can numerous other causes of migraines, it won’t hurt to eat more foods rich in riboflavin and/or take a riboflavin supplement.

Parkinson’s and other Neurological Diseases.   Riboflavin can ameliorate oxidative stress, mitochondrial dysfunction, neuroinflammation, and glutamate excitotoxicity, all of which can play a role in the pathogenesis of Parkinson’s disease and other neurological disorders (6) [7].  Alzheimer’s disease is another neurodegenerative condition in which riboflavin may play a role (7) [8].  Hyperhomocysteinemia is one possible mechanism for neurotoxicity in Alzheimer’s disease, and elevated homocysteine levels are common in those with an MTHFR C677T defect.  Earlier I discussed the importance of riboflavin in those with an MTHFR C677T defect.

Multiple Sclerosis.  Riboflavin plays an important role in myelin formation, and because of this, a riboflavin deficiency is a risk factor for multiple sclerosis (8) [9].  And so it shouldn’t be surprising that some studies show that patients with multiple sclerosis who supplemented with riboflavin or had a higher intake of dietary riboflavin showed improvements in neurological motor disability (8) [9].

High Blood Pressure.  Earlier I mentioned how FAD is a cofactor for MTHFR, and there is evidence that supplementing with riboflavin can lower blood pressure in those with the MTHFR C677T defect (9) [10] (10) [11].  So while most cases of hypertension aren’t caused by a riboflavin deficiency, if someone has hypertension and also has an MTHFR C677T polymorphism, it’s possible that supplementing with riboflavin can help to reduce their blood pressure.

Cataracts.  The depletion of lenticular reduced glutathione is a factor in human cataracts (11) [12].  As I mentioned earlier, FAD is a coenzyme for glutathione reductase, and thus a deficiency of riboflavin may be a factor in cataract formation, especially in older patients (11) [12].

Cancer.  A few studies show that a riboflavin deficiency may play a role in the development of some types of cancer.  One study showed that a riboflavin deficiency may play a role in the development of esophageal cancer (12) [13].  Another study provided evidence that a riboflavin deficiency may be associated with an increased risk of gastric cancer (13) [14].

Signs of a Riboflavin Deficiency

According to the research, having a riboflavin deficiency is rare, but when it does occur it’s usually in combination with other water-soluble vitamins.  That being said, organic acids testing evaluates riboflavin, and I do see a decent amount of people deficient in riboflavin on this test.  This panel looks at a marker called glutaric, and an elevation of this marker is a strong indicator of a riboflavin deficiency.

Some of the symptoms of a riboflavin deficiency include sore throat, redness and swelling of the mouth and throat, cracks on the outside of the lips and at the corners of the mouth, and inflammation and redness of the tongue.   I mentioned earlier that a severe riboflavin deficiency may result in decreased conversion of vitamin B6 to its coenzyme form (PLP) and decreased conversion of tryptophan to niacin.  As a result, having a riboflavin deficiency can also lead to deficiency symptoms associated with niacin and vitamin B6.

Food Sources of Riboflavin

Many plant-based foods and animal products include riboflavin.  Foods that are particularly rich in riboflavin include eggs, organ meats (kidneys and liver), lean meats, and milk (14) [1]. Green vegetables also contain riboflavin. Grains and cereals are fortified with riboflavin in the United States and many other countries (14) [1].  Many processed foods are enriched with riboflavin, along with other nutrients.  Examples include wheat flour and bread.  Of course many of these foods I mentioned are excluded from both a standard Paleo and an autoimmune Paleo (AIP) diet.

What You Need To Know About Riboflavin Supplements

Very rarely do I see someone take a separate riboflavin supplement, although many people take a B complex supplement, which of course will include riboflavin.  It’s also included in some methylation supplements, including one that I take called Methyl Protect [15].  But there are of course other methylation supplements that include riboflavin.  Most supplements that have riboflavin include it in the form of free riboflavin and/or riboflavin 5′-monophosphate.

Riboflavin Toxicity

Fortunately there is no evidence of toxicity when consuming high doses of riboflavin.  Riboflavin that isn’t converted to FMN or FAD can exist as free riboflavin and be excreted by the kidney, which causes yellow-colored urine.  I mentioned earlier that hypothyroidism is a common cause for problems converting riboflavin into FAD and FMN.

Checking Riboflavin Status

Unfortunately there is no good way to measure riboflavin through conventional labs such as Labcorp and Quest Diagnostics.  While these labs do offer testing for riboflavin, a normal reading doesn’t rule out a deficiency.  Earlier I mentioned organic acids testing as one possible way of testing for a riboflavin deficiency.

In summary, riboflavin, also known as vitamin B2, has many important functions.  It is a precursor of flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), and thyroid hormone is important for the conversion of riboflavin into FAD and FMN.  Thus, those people with low thyroid hormone levels will have problems with this conversion.  AIP-friendly foods that are rich in riboflavin include organ meats, lean meats, and green vegetables.  Organic acids testing can determine if someone has a riboflavin deficiency by looking at a marker called glutaric.