BIOTIN

Biotin is a B vitamin but has also been called “vitamin H.” Researchers have studied its role in pregnancy for decades but only recently have discovered that marginal biotin deficiency during this critical period is the norm.

Several years ago investigators tracked the biotin status of thirteen pregnant women through the course of their pregnancies, measuring a marker of deficiency in their urine. The deficiency marker increased during both early and late pregnancy in all thirteen women; in nine, it increased above the upper limit. These women, however, had none of the traditional symptoms of deficiency such as skin problems or depression. ⁴⁷

In pregnant rats, a five percent egg white diet produced a marginal biotin deficiency. The activity of biotin-dependent enzymes declined 10 percent in the mother. Yet in the fetus, the activity of these enzymes decreased a full 50 percent. Although the mother had no obvious symptoms herself, her offspring suffered an increased risk of limb and palate defects. These effects were all reversed when biotin was added to the diet in addition to egg whites.⁴⁷

Whether marginal biotin deficiency causes birth defects in humans is an open question, but the results of the rat studies merit attention to increasing one’s intake during pregnancy. Most foods contain some of this vitamin, but it is primarily found in liver and egg yolks (see Figure 4).⁴⁸

Egg whites contain a glycoprotein called avidin that strongly binds to biotin and prevents its absorption. Cooking neutralizes avidin, but not completely. Frying destroys 67 percent, boiling the egg white directly for two minutes destroys 60 percent, and poaching only destroys 29 percent.⁴⁹ Raw egg whites, then, should be strictly avoided, and cooked egg whites should be consumed in moderation—and never without the yolk. The addition of pure egg yolks to smoothies and ice cream will help boost biotin status.