Vitamin B7 - Biotin
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Skin health. Brain health. Eye health. Gene health. Biotin is key in all these, and more.
Vitamin B7 – biotin – is yet another key vitamin involved in energy metabolism. Unlike some of the other B vitamins, which may be involved in dozens, even hundreds, of different enzymes in the body, biotin is only used by a handful (five, to be precise). These enzymes are called carboxylases. The five enzymes, in case you’re curious, are propionyl-CoA carboxylase, methylcrotonyl-CoA carboxylase, pyruvate carboxylase, acetyl-CoA carboxylase 1, and acetyl-CoA carboxylase 2. These play specific roles in forming glucose (gluconeogenesis), building fats (fatty acid synthesis), and breaking down proteins (amino acid catabolism). They are fundamental, and if they aren’t working properly, major problems can crop up. One nutritionist (Chris Masterjohn, PhD) notes that biotin fuels the fire in which all our food is burned for energy. This “fire” is the citric acid cycle, and the carboxylases (especially pyruvate carboxylase) play a big part in making it run. He also calls biotin the “master builder” because it plays such an important role in amino acid and fat metabolism. And beyond its role in the metabolic fire, biotin is also involved in gene regulation and expression. This is done through biotinylating of histones, in which biotin is attached to histones, which are proteins that are key to organizing DNA in cells. As with all the other B vitamins, biotin is something that we really miss if we don’t have it.
What happens if you don’t get enough biotin? One of the most visible roles that biotin plays is in skin health—biotin is known for causing red, scaly skin (especially around the nose, mouth, and genitals), which may get infected with candida. In fact, it was initially called Vitamin H – the H stands for Haut (which means “skin” in German). If you look at the list of ingredients in your skincare products, don’t be surprised if you see biotin on it. The reason that biotin affects the skin so prominently is likely because of impaired production of essential fatty acids, which are necessary for creating the barrier of the skin. But since biotin is such a crucial component of energy metabolism, skin issues are not the only problems that arise in deficiency. Other concerns may include loss of hair, depression, lethargy, cognitive decline, numbness and tingling in the hands and feet, hearing loss, conjunctivitis, and decreased immune function.
Thankfully, frank biotin deficiency is rare—it’s in many foods and can even be made by healthy bacteria in the gut. That being said, marginal biotin deficiency may be more prevalent. This is especially true in pregnancy, with some studies suggesting that as many as 50% of pregnant women may not have enough (with some studies suggesting the number might be closer to 80%). There are also several rare genetic disorders (such as biotinidase deficiency and holocarboxylase synthetase deficiency, which occur in less than 1 in 60,000 newborns) which require supplementation. From a dietary standpoint, the classic dietary pattern associated with biotin deficiency is consumption of large amounts of raw egg whites without yolks, because egg whites contain a protein called avidin that binds to biotin and prevents its absorption. So cook those egg whites! Smoking can increase the demand for biotin (and lead to deficiency). And perhaps the most common cause of low biotin is dysbiosis, in which an imbalance in the good bacteria of the gut leads to decreases in production or absorption of biotin. We often think of this in inflammatory bowel disease (Crohn’s Disease or Ulcerative Colitis), though it can happen in many other types of dysbiosis as well (after treatment with antibiotics, or in conditions such as SIBO).
The recommendation daily allowance (RDA) for biotin hasn’t been established, but the Institute of Medicine (IOM) recommends an adequate intake (AI) level of 30 micrograms per day for most adults (the amount is slightly higher during breastfeeding and is lower for kids). The best sources of biotin (by a large margin) are liver and eggs (the AI can be met with 3 eggs). The egg whites should be cooked; the egg yolks have more biotin when they are less cooked (so make them over easy, or soft-boiled). Other foods that are good sources of biotin include other meats, fish (especially salmon and tuna), dairy, a variety of nuts (especially peanuts), seeds (especially sunflower seeds), fruits (like bananas and avocados), and vegetables (including sweet potatoes, spinach, and broccoli). Biotin can also be supplied through supplements. Unlike some of the other B vitamins, where multiple forms may be available, biotin supplementation is straightforward—it’s just biotin. Most supplements are well above the AI (often 5-10 mg, which is 15-20 times the AI). There is no known toxicity with biotin supplementation, though, and some conditions require supplementation with much higher doses (some of the genetic disorders, for example, might need 200 mg – more than 600 times the AI!). The one tricky thing to note about biotin supplements, though, is that they can sometimes throw off the results of bloodwork, so it is usually a good idea to stop any supplements with biotin before you any blood tests. Some blood tests that can be affected are thyroid tests (TSH, T3, and T4), PSA, vitamin D, and ferritin (and a handful of others).
How do you know if you have enough biotin? One approach is to track you biotin intake with a food tracker (like Cronometer). Another, easier way, is to test—this can be done with comprehensive micronutrient evaluation (like the Nutreval), or it can be done with routine bloodwork at a standard lab (like Labcorp or Quest) that checks blood biotin levels (though this is slightly less sensitive).
In summary, biotin, or vitamin B7, is a key component of energy metabolism, and plays important roles in the health of your skin, brain, eyes, and genes. While deficiency is rare, marginal deficiency is probably common. Biotin is found in a variety of foods, with liver and eggs being the best sources. If you aren’t sure where you stand, checking your levels can help you sort things out.
Are you getting enough biotin?
References
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9. Biotin biochemistry and human requirements - PubMed. Accessed July 31, 2024. https://pubmed.ncbi.nlm.nih.gov/15539280/