PROMOTING POTENTIAL 297However, other dietary factors have been associated with deleterious
eff ects, either as general undernourishment or as malnutrition (absence
of specifi c nutrients). For example, a study of protein- defi cient children
in India found substantial defi cits in cognitive test scores compared with
a nondefi cient group.^9 Perhaps most famous in this category are studies
of the consequences of famines. Th ese include the Dutch Famine of 1944,
when a German food blockade aff ected an estimated 4.5 million people.
As many as 20,000 people died. Later the Dutch Famine Birth Cohort
Study found that mothers pregnant at the time had children of below
average weight. And those children grew up to have children who were
likewise aff ected. Vari ous medical and psychiatric conditions have also
been reported in such children. Cognitive eff ects are, however, more
debatable (see below).
Causal pictures of malnutrition are oft en confused by the timing of
eff ects. In a review in 2001, Janina Galler and Robert Barrett reported
that “the brain is vulnerable to the eff ects of insults during critical periods
of brain development from the second trimester of pregnancy until
2 years of age. Malnutrition experienced at these ages will have lifelong
consequences that are not reversed by adequate nutrition. Long- term
eff ects of prenatal, postnatal and childhood malnutrition have been
reported even aft er a long period of recovery from the illness itself.”^10
Complementing these fi ndings are studies that have focused on the
eff ects of dietary supplements. Animal and human cognitive studies have
suggested that certain micronutrients (metals such as iron and zinc, or
vitamins) have specifi c, critical roles in brain development. Elizabeth
Isaacs has suggested that diff erences in protein and caloric intake can af-
fect the volumes of specifi c brain regions which (she says) are associated
with IQ.^11 Sandra Huff man and colleagues have reviewed research sug-
gesting that omega-3 and omega-6 fatty acids (found in certain fats and
oils) play an essential role in the development of the brain and ret i na:
“Intakes in pregnancy and early life aff ect growth and cognitive per for-
mance later in childhood.”^12 Since these are highly concentrated in fi sh
oils, the latter have been used in a number of intervention studies, and sold
by commercial companies, to “boost” IQ.
It would be rather surprising if nutrition was not related to cognitive
functions in some way. Th ere have been some doubts about what mediates
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