Homocysteine is an amino acid that is found in mammalian cells and in the plasma.
It arises in the first instance from the catabolism of the essential dietary amino acid
methionine, to which it is very similar in structure (Fig. 1).
Knowledge about the normal child's requirements for protein and essential amino
acids is still limited. Two approaches have been used to estimate protein requirements.
The 20 amino acids for which transfer RNA exists are the components from which
all proteins are synthesized. If they cannot be synthesized endogenously in sufficient
amounts then they are needed in the diet (1).
Classical phenylketonuria (PKU) is one of the most common inborn errors of metabolism
and affects about 1 in 7,000 white neonates. PKU is caused by deficient
activity of hepatic phenylalanine hydroxylase.
The development of obesity and associated insulin resistance involves a multitude of
gene products, including proteins involved in lipid synthesis and oxidation, thermogenesis,
and cell differentiation.
Fatty acids are an important source of energy in humans, especially during fasting.
Most tissues are able to degrade fatty acids to carbon dioxide and water, but in addition,
some organs—notably the liver—have the capacity to convert the acetyl-CoA
units produced during |3 oxidation into the ketone bodies acetoacetate and 3-hydroxybutyrate.
Reactive oxygen species, also called prooxidants, are produced physiologically during
normal metabolic reactions in the aerobic organism. However, when they are produced
in excessive amounts and are not sufficiently detoxified, the steady state balance
between prooxidants and antioxidants may be disrupted.
Inherited disorders caused by defects in the assembly or processing of glycoconjugates
are called congenital disorders of glycosylation (CDG). Until recently, these
diseases were called carbohydrate-deficient glycoprotein syndromes (CDG syndromes,
CDGS), but rapidly improving knowledge in recent years has led to the need
for a more general term (1).
Human milk is a rich source of complex oligosaccharides synthesized within the
mammary gland. The concentration of this fraction, however, varies widely with lactational
stage, decreasing from large amounts of up to 50 g/1 or more in colostrum to
an average of 5 to 10 g/1 in mature milk (1).
Arginine, a semiessential amino acid, is provided to the organism by protein intake and
newly synthesized from citruUine, in the kidney. In the liver and intestine it is the final
useful product of the urea cycle.
Celiac disease has received increased attention in recent years. It has become evident
that this is a common disorder in Western societies, affecting around 1:130 to 1:300
The ingestion of a wide range of foods by humans is accompanied by an equally wide
range of responses to those foods. While there are examples of raw foodstuffs containing
major allergens or toxins requiring special processing before ingestion, such
sources do not usually form part of the human diet.
Agriculture is the world's oldest and largest industry. For more than 10,000 years,
humans have been using biologic technologies to select and improve desired characteristics
in plants and animals for food and other uses.
Therapeutic drugs and food are often taken together. Linking drug administration to a
regular event like a meal can improve compliance with a treatment regimen, especially
in elderly people (1).
The development of cancer results from the interplay between genetic factors and the
environment, and dietary factors have been identified as modulators of almost every
step in the process.
Over the past few decades there has been significant progress in the treatment of inherited
nutrition-dependent disorders, especially the inborn errors of amino acid and
organic acid metabolism (1).
In my concluding remarks, I will round off this workshop by recalling the various papers
in chronologic order. I will give a subjective selection of some of the high points
in the presentations, without trying to summarize them.