Folic acid is another B vitamin that has a vital role in the nervous system. Pfeiffer calls it "crucial to mental and emotional health" and essential to the functioning of our brains" A deficiency usually produces irritability, along with forgetfulness and mental sluggishness. The pill limits absorption of folic acid and people using it need to supplement their diets with folic acid tablets.

Unfortunately, surveys reveal that folic acid is one of the most widespread insufficiencies in our diets. This becomes even more significant when we realize that one of the most important functions of folic acid in the body is in the synthesis of nucleoproteins, such as DNA and RNA.