There's an old saying that fish is good for the brain. This was not based on scientific evidence but presumably on "wise observation" over generations, according to Prof Ronan Gormley of UCD's Institute of Food and Health.

Most research today is focused on oily fish, rich in these omega-3 fatty acids, called eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. The latter is the one most important for brain development, while both may be beneficial for cognitive function throughout life.

Beneficial fats
Oily fish has other anti-inflammatory properties associated with reduced cardiovascular disease risk via these beneficial fats, EPA and DHA. They help to thin the blood, thereby reducing the probability of clot formation.

An analysis of 20 studies involving hundreds of thousands of participants indicates that eating about one to two three-ounce servings of oily fish a week reduces the risk of dying from heart disease by 36 per cent.

The recommended minimum daily intake of EPA/DHA varies from 250mg (EU dietary reference value) to 1,250mg (British Nutrition Foundation). Gormley suggests that an average serving of salmon or mackerel will easily supply these amounts, but to be sure to consume the brown flesh as this contains most of the oil. Unfortunately, it’s the bit I like least.

Oily fish (mackerel, herring, salmon) contain about 20 per cent protein but their water (62-70 per cent) and oil contents (10-18 per cent) vary depending on their condition.

You will know a well-conditioned fish, with a good healthy oil content, when you grill it over a tinfoil-lined tray. Droplets ooze from the fish, whereas recent spawners may show virtually no oil. Gormley advises us not to throw away the oil from the tray. Instead, pour it over your potatoes, rice or vegetables.

You may be wondering if your favourite white fish has specific healthy attributes. Does it deserve some space on your plate?

White fish (turbot, cod, hake) contain about 20 per cent protein, 77 per cent water and only 3 per cent oil. With such small levels of omega-3 fats, the focus of Irish research in 2006 by Seafoodplus was on the amino acid taurine.

Taurine, first found in bulls’ blood, is associated with osmoregulation and plays an important role in controlling blood pressure, blood clotting, neuronal activity and in maintaining a healthy heart rhythm. Taurine also acts as an anti-inflammatory agent.

Norwegian research found that taurine exhibits a synergistic effect with omega-3 fatty acids, resulting in higher healthy HDL cholesterol and lower undesirable LDL cholesterol levels, in 110 healthy human subjects.

In 2003 a study by Fennessy in Beaumont Hospital, Dublin showed that taurine (1g/day) helped to restore normal elasticity to the brachial artery of young smokers.

The positive effects of taurine on cardiovascular health continue to be the focus of researchers in the US and China.

Potential benefits
These potential benefits of taurine prompted a study by Gormley to determine levels in a number of fish species.

Over a period of months, 96 raw portions of plaice, cod, mackerel and farmed salmon were obtained from the ice counter of a Dublin supermarket and were tested for taurine content.

The mean values were 120 (plaice), 88 (cod), 63 (mackerel) and 48mg/100g (farmed salmon). The conclusion was that white fish had more taurine than oily fish among the four species.

So whatever your preference, enjoy your seafood. The general guideline is to eat two servings a week; one oily and one white. If you want to read more about the nutritional value of seafood , subscribe to Prof Ronan Gormley’s e-bulletin, Seahealth.

Herb and lemon fish and prawn casserole
This fish casserole from Just Cooking, Firies, Kerry is pretty low on the calorie front, when enjoyed with a fresh green salad. It's big on taste, antioxidants and flavonoids too and a great way to introduce seafood to younger family members.
Serves 4
2 tbsp olive oil
2 garlic cloves, finely chopped
2 red onions, sliced
Zest of 1 lemon, finely grated
1 red pepper, cored, cut into strips
1 yellow pepper, cut into strips
50ml white wine (optional)
1 bunch scallions, finely sliced
1 leek, trimmed and sliced
1 large fennel bulb, thinly sliced
2 x 400g tins of good quality chopped tomatoes
2 tbsp chopped fresh chives
2 tbsp chopped fresh coriander
500g skinless firm white fish fillets (such as cod, haddock or halibut), cut into bite-sized pieces
200g raw tiger prawns, peeled and de-veined
Freshly ground black pepper

Heat the oil in a shallow casserole dish over a medium heat and add the onions and garlic. Cover and cook slowly, without allowing them to brown, for about six minutes or until the onions are beginning to soften.

Add the peppers, leek, lemon and fennel and cook, stirring, for two minutes. If using, add the wine and allow to evaporate until there is a tablespoon left.

Add the chopped tomatoes and black pepper. Bring to the boil, add the fish, bring to a simmer and cook uncovered, for 10 minutes.

After 10 minutes, add the prawns and cook for a further four to five minutes or until the fish is fully cooked. Stir in the chopped fresh herbs and serve.

Turbot with crushed potatoes and sauce vierge
Serves 4
1 tbsp rapeseed or olive oil
4 fillets of turbot
Juice of ½ lemon
Lots of black pepper

Heat a pan with a little oil and pan fry fish on both sides until they are golden brown (two to three minutes on each side should be sufficient). Season the fish on the pan with a little lemon juice and pepper.

Crushed potatoes with olive oil
12-16 baby potatoes
2 tbsp olive oil
1 tbsp chopped parsley

Cut the potatoes into cubes (no need to peel them) and place them in a large saucepan of water. Bring to the boil and simmer until tender. Drain the potatoes well, and then add in the chopped parsley and the olive oil and mash gently with the back of a fork.

Sauce vierge (Dunbrody House)
This tangy, chunky sauce goes particularly well with fish. Mix ingredients below to serve four.
50ml olive oil
1 tbsp balsamic vinegar
6 coriander seeds crushed
2 tbsp lemon juice
1 tbsp finely chopped shallot
1 tbsp chopped tarragon
1 tbsp chopped chives
1 tbsp chopped coriander leaves
1 tbsp concasse tomato

Paula Mee is lead dietitian at Medfit Proactive Healthcare and a member of the Irish Nutrition and Dietetic Institute. medfit.ie Tweet @paulamarymee