Making fish a foe may affect growing foetus

Shunning raw fish during pregnancy for fears of toxicity has meant women are lacking in fatty acids that are essential for a growing baby’s brain and vision.

In an online survey of 596 women in their third trimester by nutritionists at Massey University, only 30 per cent were getting their recommended intake of two to three servings of essential polyunsaturated fatty acids per week.

The deficiency was put down mostly to the demonisation of fish, said Dr Cath Conlon, who co-authored the study with Dr Michele Eickstaedt, and Dr Kathryn Beck.

Conlon said there was a lot of mixed messages around how pregnant women should prepare fish and what’s safe to eat.

‘‘Then there’s the aspect on potential for fish to be contaminated by mercury, and that would have a detrimental effect for the foetus.

‘‘So when you hear those messages it’s easier to say ‘I’ll cut fish out of my diet’. We want women to know a lot of fish available in New Zealand is safe for them to eat.’’

"We want [pregnant] women to know a lot of fish available in New Zealand is safe for them to eat."

Dr Cath Conlon, study co-author

While the consequences of a diet low in these fatty acids - Omega 3 and Omega 6 - were not fully understood, it was known to be important in the growth of the brain and eye development in a foetus, Conlon said.

‘‘What we don’t know is how, during pregnancy, the body will regulate certain pathways. We don’t know how much compensation goes on in the body.’’

The study involved an online questionnaire, promoted through district health boards and health clinics across the country. It was published in the New Zealand Medical Journal today.

Mercury contamination is greatest among fish that live a long time and lurk the bottom of the sea, Conlon said. So those that don’t live long – including tuna, farmed salmon, mackerel or sardines, tarakihi, blue cod, hoki, john dory, monkfish, warehou, whitebait and flat fish like flounder – are seen as low risk.

One fifth of the women surveyed were taking Omega-3 supplements. On average, they were more than 16 times more likely to meet recommendations for docosahexaenoic acid (DHA).

Women who are pregnant or planning to become pregnant should aim to eat a variety of foods from the four food groups every day, including cooked fish, the researchers said.

But no fish should be eaten raw and soft cheese was still off the table.

‘‘It’s really important women do eat a healthy diet and they have a variety of foods and don’t limit to a small range.’’

If in doubt, check with health professionals, Conlon said. Things like salmon and hoki and those commonly available fish are usually safe.

The World Health Organisation recommends two to three 150g servings of most fish types, low in mercury, per week.

Conlon said the researchers would like to see a concerted effort towards educating pregnant women on what they can eat, rather than long lists of ‘‘cannots’’.