Fish is a good choice for the protein portion of a balanced diet, and can offer positive health benefits. White fish such as cod, plaice and haddock are low in fat and therefore a good protein source when following a low-fat diet.
Oily fish such as salmon, trout, sardines, mackerel and pilchards (tinned, fresh or frozen) are higher in fat than white fish, and contain a special type of polyunsaturated fat known as omega-3 fat. White fish contain some omega 3 but at much lower levels than oily fish.
This type of fat has been shown to help protect against cardiovascular disease. It also helps to lower a type of fat in your blood known as triglycerides.
How much should I eat?
People with diabetes are at increased risk of cardiovascular disease and are therefore encouraged to try to eat oily fish at least twice a week (a portion is about 140g cooked). This is higher than what is recommended for the rest of the population, who are encouraged to eat at least two portions of fish a week, one of which should be oily.
Even though oily fish is higher in fat and calories, it is still a good choice – even if you are trying to lose weight – as it reduces the risk of cardiovascular disease.
Women who aren’t going to get pregnant in the future, men and boys can eat up to four portions of oily fish a week. Girls and women likely to become pregnant in the future should stick to a maximum of two portions of oily fish a week, as should women who are pregnant or breastfeeding.
Pregnancy and children
Pregnant women should avoid marlin, swordfish and shark due to the risk of exposure to methyl mercury. At high levels this can be harmful to the development of the baby. Children should avoid marlin, swordfish and shark, as these levels of mercury in these fish can affect the development of children’s growing nervous systems. Adults should limit their intake to one portion a week.
Vitamin D
Oily fish is generally rich in vitamin D, which is important to maintain calcium balance in the body. Most of us make our own vitamin D when our skin is exposed to sunlight, but eating foods that contain vitamin D is essential for people who are housebound or rarely expose their skin to sunlight.
Fortified foods
Foods fortified with omega-3 fatty acids contain relatively small amounts and will only make a small contribution towards helping people meet their nutritional requirement.
Fish oil supplements
Diabetes UK can only make general recommendations for all people with diabetes. Because everyone’s needs are so different, we cannot give individualised advice.
We do not generally recommend that people with diabetes take any kind of supplement, as there is not enough evidence available to support their use in diabetes care. Pharmacological doses of fish oil supplements (eg greater than 3g daily) also have the potential to worsen blood cholesterol levels, especially LDL cholesterol (the bad type of cholesterol).
There is clinical evidence both for and against the use of fish oil supplements. People with diabetes should consult their doctor if they already take fish oil supplements, or if they are thinking about taking them. People who are taking high doses of fish oil supplements (greater than 3g per day) should ask their doctor to monitor the effect on their cholesterol and triglyceride levels.
Medication
As with starting any new treatment (including fish oil supplements), people with diabetes should monitor their diabetes control more carefully to check the effect of the treatment they are taking. Fish oil supplements can adversely interact with medications including warfarin, aspirin and clopidogrel and should only be taken after discussion with your doctor.
Myocardial infarction
NICE provides specific advice for people who have had a myocardial infarction (MI – also known as a heart attack), and recommends that people who have had an MI in the last three months should aim to consume 7g of omega 3 fatty acids per week from two to four portions of oily fish and provides detailed advice on this. People who have had an MI in the last theee months should speak to their healthcare team for individual advice.
Plant omega 3
It is more difficult to reach your omega 3 requirements if you are vegetarian or vegan. However, you can increase omega-3 in your diet by including more green leafy vegetables, walnuts, linseeds, rapeseed, walnut and soya oils as part of a balanced diet. Some foods, such as eggs, milk, bread and margarine, are fortified with omega 3.
Reviewed: May 2012
Next review: November 2013