Biotin: Is extra beneficial for pets’ skin and coat?

Biotin is a water-soluble B vitamin identified as a metabolic requirement for cats, dogs and other companion animals; however, its need in the diet may be conditional.

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Biotin is a water-soluble B vitamin identified as a metabolic requirement for cats, dogs and other companion animals; however, its need in the diet may be conditional. This vitamin serves as a coenzyme for five vital carboxylase enzymes and is involved in gluconeogenesis, synthesis of fatty acids and branched-chain amino acid catabolism (e.g., isoleucine and valine).

Aside from an inborn error in metabolism, deficiencies are not reported for companion animals and cases of deficiency are rare. These few deficiencies are relegated to clinical research situations where the insufficiency was induced in kittens fed a total raw egg white diet or with parenteral feeding in which biotin was devoid. In these cases, deficiency led to hair loss, scaly dermatitis, weight loss, diarrhea and neurological impairment (Carey and Morris, 1977).

Because of this association with structural protein issues (hair, skin, nails) leading to dermatitis and hair loss when biotin was bound or absent, the vitamin often gets associated with maintenance of the dermis and attributed with support for skin and coat health. Which may be why we see many products in the market, including foods, treats and supplements, that purport benefit to skin and coat condition from super-fortified levels of biotin. But do we know enough about its origin and safety to pursue these promotional benefits?

The egg played a  pivotal role in the discovery of biotin. The yolk has a very rich concentration, but the glycoprotein avidin in the white binds biotin, rendering it nutritionally unavailable. This binding played a leading role in understanding how biotin functions. Since avidin is a protein, it is denatured by cooking, so unless fed a diet of raw egg white, biotin deficiency in dogs and cats is not a likely occurrence.

Biotin is commonly found in foods. Bioavailability can vary among feedstuffs, from 50% for wheat, barley, triticale and sorghum to >86% for corn, soybean meal, and meat and bone meal (in poultry; Baker, 1995). In meats and cereals, biotin is covalently bound to proteins and released during digestion by biotinidase enzymes. While it needs to be confirmed in dogs and cats, in other mammals biotin in the plasma is shuttled throughout the body in a free unbound form.

Aside from dietary sources, some biotin is produced by colonic fermentation and there is evidence to suggest it can be absorbed into the circulation via the coloncytes. Since a portion of the animal’s biotin supply is produced in the lower bowel, antibiotics such as sulfonamides may alter the gut microflora and indirectly create a biotin deficiency.

If dietary conditions, genetics, species or feeding practices dictate, supplemental biotin may be necessary. Many nutritionists will supplement biotin routinely as a precaution for when the animal’s digestion is disturbed or when they are unexpectedly placed on antibiotics. Supplemental biotin is sold as a 2% active ingredient white powder. For commercial petfood production, it is best handled as part of a vitamin premix.

This biotin is synthesized using fumaric acid as the starting material in a procedure developed by Hoffman-La Roche scientists Sternbach and Goldberg and patented in 1949. The result of this process is biologically active d-biotin. Their method, with refinements, is in use to this day. Alternative methods have been developed and are being perfected to utilize fermentation by fungi to produce “natural” biotin. Total global output is estimated at 100 metric tons per year and China accounts for nearly 80% of the supply.

The Nutrient Requirements of Dogs and Cats (NRC, 2006) states for both that “For normal diets not containing raw egg white, adequate biotin is probably provided by microbial synthesis in the intestine. Diets containing antibiotics may need supplementation.” It does not provide a recommended allowance for dogs, but for cats it suggests 18.75 ug/1,000 kcal ME, regardless of lifestage. Additionally, there is no recorded toxicity or safe upper level for either dogs or cats. This is good because formulators must account for processing losses. In canned petfoods, biotin can be lost at 40–70%. In dry petfoods, sacrifice can be 10% through extrusion, 10% through drying and another 2.4% per month thereafter (BASF, 2000).

Biotin appears to be  a well-characterized molecule that is needed in very small quantities and has a long history of safe use. It most certainly fits within the framework of commercial petfoods fortified to cover the nutritional needs for the breadth of pets intended to be fed. Additionally, biotin has been demonstrated to impact skin and coat quality (Volker, 1979; Frigge et al., 1989; Marsh, 1999).

However, while plasma levels increased with increasing supplemental biotin in dogs, supplementation beyond baseline needs were not shown to improve skin and coat quality of otherwise healthy animals (Tran et al., 2007). Thus marketing claims for skin and coat benefit may need to be explored a bit more to determine the exact circumstances in which super-fortified levels are beneficial.

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