NUTRITIONAL DISORDERSCZhhVg6]bZY!BVjgZZc9Vlhdc!8]g^hHb^i]:YLddY '*.
result from starvation, cardiac arrest or other complications. Sufferers of AN
are often of above average intelligence but generally have a grossly dysmorphic
view of their own bodies, seeing themselves as obese, even though they ‘know’
they are underweight. It is unclear as to what causes this view. It has been
suggested that overreactions to relatively mild obesity, peer or social pressures
regarding an ideal human shape or a wish to delay the onset of menarche may
all be linked to the condition.
Bulimia nervosa is characterized by episodes of excessive or ‘binge’ eating that
induce feelings of guilt such that sufferers induce vomiting to void the food.
This cycle of eating and induced vomiting can be repeated many times. As with
anorexics, the use of laxatives, diuretics and dieting pills may be abused. The
condition tends to affect older patients than those with anorexia. The signs
and symptoms of BN include puffy cheeks due to enlarged salivary glands
and often severely damaged tooth enamel because of the excessive vomiting.
Electrolyte imbalance, such as loss of potassium, can cause health problems
and increases the risk of cardiac arrest (Chapters 8 and 13 ). However, patients
generally manage to maintain their weight at an appropriate value and so the
condition may not be noticed and can remain undetected for many years.
Disorders of Vitamin Nutrition
An inadequate dietary intake of a vitamin, its impaired absorption, or
insufficient utilization of an adequate intake, increased dietary requirements,
for example in pregnancy, without a corresponding increased intake or
an increased excretion of a vitamin give rise to hypovitaminoses. In many
cases, the symptoms of a hypovitaminosis can be correlated with the known
functions of the vitamin (Section 10.2), although in other cases they are
rather generalized. Hypovitaminoses often develop over an extended period.
Initially there is depletion of body stores with a biochemical impairment, that
is a subclinical deficiency. This eventually results in an overt deficiency with
frank signs and symptoms and is usually accompanied by other evidence of
malnutrition, for example PEM. A covert deficiency does not present with
clinical features under normal conditions, but any trauma or stress may
precipitate the hypovitaminosis. Starving individuals will suffer from multiple
vitamin deficiencies. At the other extreme, an excess of the vitamin can be
toxic and may result in a hypervitaminosis.
Hypovitaminoses
A deficiency of vitamin B 1 or thiamin in some developing countries is common
because of the high consumption of foods, such as polished rice, where the
vitamin is lost during milling, and in chronic alcoholics, who often have a poor
diet. The consequences of a deficiency are depression, irritability, defective
memory, peripheral neuropathy and beriberi. Beriberi, which literally means
‘I cannot, I cannot’ in Singhalese, occurs in two forms, which affect different
body systems. Dry beriberi mainly affects the nervous system, wet beriberi
the heart and circulation; both types usually occur in the same patient but
one set of symptoms predominates. Patients with the dry form may present
late, with polyneuropathy and Wernicke-Korsakoff syndrome (Box 10.4). The
polyneuropathy is characterized initially by heavy, stiff legs, then weakness,
numbness and paresthesia and absent ankle jerks. Later stages involve the
trunk and arms. Wet beriberi, also known as shoshin, from the Japanese for
acute heart damage, is less common and characterized by edema. Symptoms
appear rapidly with acute heart failure in addition to the polyneuropathy. It is
highly fatal and known to cause sudden deaths in young migrant laborers in
Asia whose diet consists of white rice.
Vitamin B 2 (riboflavin) deficiency is rare in the developed world and usually
only seen in alcoholics who normally have diets lacking other nutrients or