• I'm pregnant, should I be eating lots of oily fish; I've heard it's good for my baby?
• Should I take supplements?

I'm pregnant, should I be eating lots of oily fish; I've heard it's good for my baby?

There is evidence that eating oily fish may have a beneficial effect on the length of pregnancy and the babies' nervous system development. However some fish can contain higher levels of chemicals and mercury than we would really like. Therefore the advice is to avoid eating certain fish like shark, swordfish and marlin. These are big fish that live a long time; therefore there is more time for the chemicals to build up.

It is also advisable to limit the amount of tuna you eat to no more than two tuna steaks a week (weighing about 140g cooked or 170g raw) or four medium-size cans of tuna a week (with a drained weight of about 140g per can) for the same reason.

In total you should have no more that two portions of oily fish a week if you are pregnant. But remember that eating fish is good for your health and the development of your baby, so you should still aim to eat at least two portions of fish a week, including one portion of oily fish.

For a list of oily fish see, the fish oils and omega 3 page.

Should I take supplements?

In this country we spend millions of pounds on supplements. In certain populations there is excellent evidence of the good that they do (mostly in people who are ill), however there is little evidence that they provide massive health benefits for healthy people.

Pregnancy is an exception and there are two nutrients which women are advised to take a supplement of, folic acid and vitamin D.

400mcg folic acid supplements are most beneficial when they are taken before conception and then up to the end of the first trimester, and taking folic acid has been shown to protect against spinal cord defects, such as Spina Bifida. Folic acid supplements for pregnancy are available on prescription or you can buy them from a pharmacy.

Some people presume that if something is good for you, them more of it must be even better. This is certainly not the case with supplements and no supplement should be taken at ‘mega doses'. The only exception during pregnancy is women with certain medical conditions, including diabetes, who will be prescribed a 5mg supplement of folic acid.

The government now recommends that all women who are pregnant should take a vitamin D supplement of 10 mg. There is currently no single vitamin D supplement available at pharmacies, so if you wish to take vitamin D, you may have to take it in conjunction with calcium (as this is what it is most commonly prepared with). Again only take the recommended amount, not mega doses.

There has been evidence for the harm of large doses of some supplements for a long time. Vitamin A (retinol) supplements, for example, should not be taken in pregnancy as they can cause harm to the unborn baby. There is always research going on into supplements, for example, a recent study has shown that that vitamin E supplements taken during pregnancy can increase the risk of heart defects in babies.

It is important to remember that there are many sources of information and not all of them are reliable. While research like this is at the fore front of science it is not perfect, and sometimes later research conflicts with current thinking. However there are increasing numbers of studies that suggest that taking large doses of supplements does not have any health benefits and may even do harm.

Many women choose to take a multi-vitamin as a ‘back up' in case they do not get everything from their diet. There is no evidence that this does any harm, so do not worry if that is something you choose to do so. However make sure the supplement contains a maximum of 100% of the RDA's of vitamins and minerals and no retinol. If in doubt about which is suitable, ask your pharmacist.

Without vitamins and minerals in suitable amounts the human body cannot function, they are essential parts of the diet; however there are many things in food that, although not essential, may have health benefits. Eating a varied balanced diet, rich in fruit and vegetables should ensure that you get everything you need for a healthy pregnancy and it is important to remember that not everything can be contained in a tablet.