The fatty acids that fish oil contains are vitally important to the developing brain, says a new study, suggesting that women maintain a balanced diet rich in these fatty acids for themselves during pregnancy and for their babies after birth.

Dietary deficiencies in the type of fatty acids found in fish and other foods can limit brain growth during foetal development and early in life, the findings showed.

Deficits in what are known as n-3 polyunsaturated fatty acids cause molecular changes in the developing brain that result in constrained growth of brain cells and the synapses that connect them, said Susana Cohen-Cory, professor of neurobiology and behaviour at the University of California, Irvine (UCI).

These fatty acids are precursors of docosahexaenoic acid, or DHA, which plays a key role in the healthy creation of the central nervous system.

Dietary DHA is mainly found in animal products: fish, eggs and meat. Oily fish - mackerel, herring, salmon, trout and sardines - are the richest dietary source, containing 10 to 100 times more DHA than non-marine foods such as nuts, seeds, whole grains and dark green, leafy vegetables.

In their study, which used female frogs and tadpoles, the UCI researchers were able to see how DHA-deficient brain tissue fostered poorly developed neurons and limited numbers of synapses, the vital conduits that allow neurons to communicate with each other.

"Additionally, when we changed the diets of DHA-deficient mothers to include a proper level of this dietary fatty acid, neuronal and synaptic growth flourished and returned to normal in the following generation of tadpoles," Cohen-Cory said.

The study appeared in The Journal of Neuroscience.