Does eating whole raw eggs lead to biotin deficiency?

Question

I've been looking into this and can't seem to find it anywhere. I know that the raw egg whites can lead to a biotin deficiency, but I'm wondering if eating the yolk as well negates this. Please note that the eggs are pasteurized to prevent salmonella.

I just find that I've never really liked cooked eggs, but can happily consume 10 a day in a smoothie before and after training with a little bit of milk and 20ml maple syrup.

Answer 1

Biotin is an important nutrient. Biotin deficiency was at least thought to be very rare. Unless the diet was for the main part composed of raw egg white it was assumed to be only of concern in certain subgroups like severely malnourished children. But deficiency might actually be much more widespread:

The importance of biotin for human health has been under-appreciated for many years. Health professionals thought that the role of biotin in human well-being was limited to that as a coenzyme for carboxylases and that biotin deficiency was fairly rare in free-living humans. This view has changed considerably over the past few years. Evidence has been provided that marginal biotin deficiency might be more common than widely believed, particularly in certain subgroups of the general population, such as pregnant women, patients treated with certain drugs and severely malnourished children.

The component responsible for this phenomenon is the substance avidin that is an antinutrient and biotin binding substances are mostly found in the white but also the yolk for humans since the binding produced by the biotin and avidin is apparently stronger than digestive juices.

Avidin is glyco-proein that binds to any biotin so consuming egg yolk does not "negate" that. Egg yolk does not contain anything that reverses or prevents this bond. Biotin of any source, for example synthesised by gut bacteria, is subject to being captured by consumed avidin. Eating a lot of egg white means one has to eat that much more biotin, that conveniently is also present in the yolk – to compensate for the losses due to avidin consumption.

To really develop clinical manifestations of biotin deficiency it usually might take a while. But consuming lots of raw egg white seems to be not a very good idea.

Although the following mentions pets and the effect of denaturation on avidin by cooking seems under debate now, this paragraph illustrates it well:

A syndrome termed “egg white injury” was first described in the 1920s. Animals fed raw egg whites as a component of their food developed a scaly skin rash, elevated blood cholesterol levels, and defects in nerve transmission. Eventually, the underlying cause was identified as a deficiency of biotin, brought about by an inhibitory substance in egg white that decreased availability of biotin. This factor was named “avid-albumin” or avidin. Avidin is a protein that is a secretory product of the hen’s oviduct and is subsequently deposited in the albuminous portion of the egg. When consumed, avidin combines with dietary biotin in the intestine and prevents its absorption. The avidin in egg white is so effective in this capacity that raw egg white has been used to experimentally induce biotin deficiency in laboratory animals. Regardless, the danger of a pet owner inducing a biotin deficiency in a dog or cat by feeding supplemental eggs is slight because the yolk of the egg contains large quantities of biotin. In addition, cooking eggs denatures avidin and destroys its biotin binding ability. Practically speaking, potential risk for biotin deficiency will only occur if an owner supplements the pet’s food with only the white of the raw egg. As in other species, signs of biotin deficiency in dogs and cats include dermatitis, loss of hair and poor growth rate.

Answer 2

There's more biotin in the whole egg than can be bound by the avidin, according to the following outline:

Avidin: 180 μg per egg; molecular weight is 66–69 kDa, let's say 66 kDa. One molecule can bind 4 biotin molecules.

Biotin: Up to 25 μg per large egg, let's say 10 μg to be conservative; molecular weight is 244.31 Da.

The fraction of biotin that can be bound by avidin is

(4 * 180 / 66000) / (10 / 244.31) = 27%.

This means that the majority of biotin remains freely available and that the whole raw egg is a good net source of biotin.