I'm confused about oily fish. I thought it was important to eat things such as salmon and mackerel because we need the omega-3. I want to start a family soon, but I've been told to limit my intake. What are the facts and can my husband eat more than me?
Jo, West Sussex

The whole oily fish debate is a bit of a minefield. The one basic rule for child-bearing women is not to eat more than two servings of oily fish a week. A serving is around 140g raw and 170g cooked weight.

This is because, although oily fish gives us omega-3 (two servings give us around 3g), which is essential for the healthy development of a baby's brain, sadly, our polluted waterways and oceans mean that these same fish have accumulated toxins in their bodies known as dioxins and PCBs.

When we eat the oily fish, we eat these pollutants, which build up in our bodies and can be harmful to a developing baby. Although you cannot change the levels of dioxins and PCBs already in your body, you can avoid consuming too many more by sticking to these guidelines.

The term “oily fish” includes fresh and canned salmon, mackerel, trout, herrings, sardines, pilchards, kippers, eel, whitebait, anchovies, swordfish, bloater, carp, sprats and some more unusual sounding ones such as jack fish and katla as well as fresh tuna steaks. Canned tuna has its own criteria. This is because, unlike other oily fish, tuna is cooked prior to canning and loses most of its oils and thus pollutants (and omega-3). You can therefore have up to four 140g servings of canned tuna a week.

Not so long ago, this was pretty much all you had to remember and you could eat what you liked of white fish. Unfortunately, recently surveys have found that sea bream, turbot, halibut, huss and sea bass as well as crab may also have similar levels of dioxins and PCBs as oily fish, so you need to include these in your two servings a week.

Fish such as coley or hake, haddock and red snapper are apparently OK because they have much lower levels of pollutants.

When it comes to your husband, he can have up to four servings of oily fish a week. The omega-3 may help to protect his heart and so it is worth encouraging.

It is important to remember that, amid these rather gloomy rules, all fish is great for protein that is needed for growth and development, and that oily fish gives us good amounts of iron, selenium and vitamin D, which women in the UK especially tend not to do very well on. So follow the guidelines and enjoy the fish you do eat with gusto.

Food fortified with omega-3

Salmon from Marks & Spencer has been specially bred to give you double the omega-3 of normal salmon. One serving a week will meet your omega-3 needs.

If you are pregnant, or trying to be, avoid shark, swordfish and marlin, which contain more mercury than other fish.

Omega-3 oils from flaxseeds, linseeds, walnut and rapeseed are not the same as those in fish and it is unclear if they have the same benefits. When buying omega-3 fortified food, check the source. Those with omega-3 vegetable oils (“ALA” on the label) may not be as useful as those from fish oils (described as EPA and DHA). Aim for 3g a week of EPA and DHA.

If you have a nutrition question, e-mail: amandaursell@thetimes.co.uk

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