Biotin, also known as vitamin B7 or vitamin H, is a cofactor which aids in the metabolism of fats, carbohydrates, and proteins. Biotin deficiency due to diet is pretty rare, but eating raw egg whites for an extended period of time can deplete the body of biotin. Foods that are high in biotin include egg yolks, nuts, meat, and dairy.
The Linus Pauling Institute website has a great in-depth review of biotin that includes information on deficiency symptoms and the function of this vitamin in the body.
Biotinidase is the enzyme that is involved in the extraction of biotin from food and also in the recycling of free biotin that has been used in another reaction in the body.
Profound biotinidase deficiency is defined as having less than 10% of normal enzyme activity, and partial biotinidase deficiency is defined as having between 10% and 30% of normal enzyme activity.
Note that not everyone with a BTD variant is affected by biotinidase deficiency[ref], but for most, a homozygous polymorphism will result in biotinidase deficiency.
So what happens if you are heterozygous for one of these polymorphisms? There isn’t a lot of concrete information about it, but it seems that you would produce less of the biotinidase enzyme and thus get less biotin from food sources. Biotin is a water soluble vitamin and not thought to be toxic at higher levels, so trying a biotin supplement may be worthwhile.
Check your genetic data:
rs13078881 (C is the minor allele, also known as D444H)
- Polymorphism reduces enzyme activity to just less than half of normal [ref] If combined with other heterozygous BTD polymorphisms, it can result in partial or profound biotinidase deficiency.
The following SNPs are considered pathogenic for biotinidase deficiency for those who are homozygous for the minor allele. (This is not a complete list.)
rs28934601 (G is the minor allele)
rs13073139 (A is the minor allele)
rs34885143 (A is the minor allele)
i6008460 (G is the minor allele)
i6008458 (A is the minor allele)
i6008480 (C is the minor allele)
i6008436 (C is the minor allele)
What to do with this information:
If you are heterozygous for one of the BTD polymorphisms and have symptoms of biotin deficiency, biotin supplements are readily available. It is a water soluble vitamin and not known to be toxic. Good food sources of biotin include nutritional yeast, which has over 200 mcg per 100g, and chicken liver which has 170 mcg per 130g. [ref]