ESSENTIALITY OF DIETARY OMEGA 3 FATTY ACIDS IN PRIMATES

DESCRIPTION The essentiality of dietary n-3
fatty acids remains an unresolved issue in human nutrition. The high
content of docosahexaenoic acid (22:6n3 or DHA) in the phospholipids of
retina and cerebral cortex suggested an important role in photoreceptor and
neuronal membrane functions. We have observed significant effects of n-3
fatty acid deprivation in rhesus monkeys during combined prenatal and
postnatal development. DHA levels in retinal and brain phospholipids were
greatly reduced, and visual acuity development and electroretinograms were
abnormal. Effects on the electroretinogram (ERG) were not reversible by
refeeding with fish oil or pure DHA at 10 months or older. Behavioral
effects included large increases in fluid intake (polydipsia), increased
stereotyped behaviors, and persevering errors in a learning task. Monkeys
deprived only postnatally showed similar ERG changes and polydipsia. They
propose new studies with rhesus monkeys to investigate some remaining
critical questions about the effects of dietary n-3 fatty acid deficiency:
(1) What dietary n-3 fatty acid is optimal for functional development?
Should infants receive preformed DHA or can they synthesize sufficient DHA
from dietary alpha-linolenic acid? (2) What minimum amount of dietary n-3
fatty acids is needed to promote normal postnatal development? Are
sufficient quantities provided by some widely-used human infant formulas?
(3) Can effects of the deficiency on retinal function be reversed by
refeeding with n-3 fatty acids at ages earlier than 10 months, and can a
critical period be defined? (4) Can effects of low dietary n-3 fatty acids
be separated from those of high n-3 fatty acids? (5) Does n-3 fatty acid
deficiency affect sensory systems other than visual; and does the
deficiency affect complex cognitive abilities including learning and
memory? (6) How does the deficiency alter phospholipid molecular species
composition, activity of key enzymes in brain phospholipid metabolism,
vitamin E and peroxide levels in plasma and tissues, and lipofuscin
accumulation in the retina and other tissues? These studies will help to
determine nutritional needs for n-3 fatty acids during development and to
establish the role of these fatty acids in neural functioning. The
research has important implications for optimum diets of pregnant and
lactating women as well as infants and children.