91av

IF YOU want brainy children, eat the occasional oily fish when you’re
pregnant. That’s the message to would-be mums from a British follow-up study of
435 pregnant mothers and their children.

Cathy Williams, Kate Northstone and their colleagues at the University of
Bristol discovered the value of oily fish such as sardines and mackerel through
the “Children of the 90s” study of thousands of mothers in the Bristol area. The
investigators asked 435 women to keep a detailed diary of what they ate during
pregnancy.

Three years later, they tested how well the children recognised depth in 3D
images, or “stereopsis”. “It’s a proxy measure for brain development,” says
Williams. “The cells which enable you to do this are in the visual cortex, so
it’s [a test of] brain rather than eye function.”

Children of mothers who ate oily fish at least once a fortnight during
pregnancy had the best scores for stereopsis, rated as adult, medium or poor.
“Children of mothers who ate fish were one and a half times as likely to have
adult-grade stereopsis as children whose mums hadn’t eaten any fish,” says
Williams.

She and her colleagues suspect that the cause might be abnormally high levels
of docosahexaenoic acid (DHA) in oily fish. “That’s what many people think is
the magic ingredient,” says Williams.

This fatty acid is a major structural component of brain, nerve and eye
tissue, and plays a vital role in the early development of these organs. It is
abundant in breast milk. Arguments have raged over whether to add it to formula
milk for babies
(91av, 18 March 2000, p 16).

Williams stresses that further investigation is necessary. “You don’t need to
eat much fish,” she says. There might be a downside to eating too much, such as
exposure to pollutants which accumulate in fish oil and in body fat.