CASE FILES: BIOCHEMISTRY
A N SW E R S TO C A SE 41: V E G E T A R IA N
D IE T -E S S E N T IA L A M IN O A C ID S
A 37-year-old female who is planning to undertake a radical new
vegetarian diet is in your office for counseling.
Essential amino acids: The amino acids that cannot be synthesized by
the body. There are a total of nine essential amino acids.
List of essential amino acids: Histidine, isoleucine, leucine, lysine,
methionine, phenylalanine, threonine, tryptophan, and valine.
C L IN IC A L C O R R E L A T IO N
The vegetarian should be careful to ensure a balanced ingestion of proteins,
fats, carbohydrates, and vitamins. Most animal proteins contain all the essen-
tial amino acids; however, vegetable proteins often lack one or more of them.
Often, plant amino acids are of low biologic value and incompletely digested.
Vegans often benefit from nutritional consultation, which would allow the
patient to make sure that she ate foods that complemented each other in pro-
viding the essential amino acids.
A PPR O A C H TO E SSE N T IA L A M IN O A C ID S
Be aware of the importance of essential amino acids.
Know about the synthesis of other amino acids.
Be aware of some of the problems with inadequate essential amino
Essential amino acids: Amino acids that the human body cannot synthe-
size (or cannot synthesize in sufficient quantities to meet cellular needs)
and must be taken in the diet. If essential amino acids are deficient, the
result is a condition of negative nitrogen balance.
Nonessential amino acids: Those amino acids that are synthesized by the
human body in sufficient quantities to meet cellular needs.
Phenylalanine hydroxylase: The enzyme that converts the essential amino
acid phenylalanine to the amino acid tyrosine using tetrahydrobiopterin
and molecular oxygen. A genetic deficiency in this enzyme gives rise to
the disease phenylketonuria.