The Fish Foundation

Nutrition Aspects

Home Page


Micronutrients Omega-3 Dietary Sources Fats & Oils Macronutrients Balance

This section of the website explains the biochemical, nutritional and medical   aspects  which underpin all that the site is about. 





This section deals with the wider nutritional aspects of seafoods, starting with a look at the types of fish and shellfish which are important in human food (in the UK), then  looking at the macronutrients such as    protein, fats/oils etc.,  and finally the minor nutrients and components (e.g vitamins and minerals). A brief look at the problem of toxins in seafoods, and a perspective on the significance of seafoods in the human diet brings the section to a close.


Types of Seafood

The foods we derive from the aquatic environment fall broadly into two major categories, fish and shellfish. The marine mammals, such as whales, dolphins, seals and porpoises, do not constitute a major food source, at least for Western Europe, so will not be considered further.



Though fish can come from freshwater and/or saltwater environments, from a nutritional point of view there is not a big difference, so this distinction will not be explored further. The major division within the fishes is between those with bones, and those without, the so-called cartilaginous fish. The latter include sharks, skate, rays and dogfish. Dogfish (also known as huss, or rock salmon) and skate are moderately popular in the UK, accounting for around 2% of fresh fish landings. The remaining 98% (excluding shellfish) is made up of the bony fish, and this group is split into two, on the basis of feeding habits.

Demersal fish

This group represents just over half of all UK fresh fish landings, and consists of the so-called white fish, the low-fat fish. Demersal fish feed deep in the water, or even on the sea-bed, and catching technology is adapted to this. Cod, haddock, plaice and whiting make up 65% of this group, with sole, saithe/coley, ling and monkfish important members of the rest.

Pelagic fish

These are fish which feed more in the surface layers (though at different stages of the breeding cycle, some pelagic fish can temporarily become demersal). The pelagic fish are primarily those with higher levels of lipid in the flesh, which gives them non-white flesh. The major members of this group are herring and mackerel, which make up over 90% of fresh pelagic landings in the UK. Spratts, pilchards (mature sardines) and tuna are also sometimes landed in the UK, though tonnages are not large at present. Nutritionally, salmon and trout are probably closer to this group than any other. Being mainly farmed fish, there are few reliable published figures to indicate production or consumption levels, but both are significant contributors to fish intake.


This group includes not only the creatures we normally think of as shellfish, but other marine life-forms without apparent shells, such as squid and octopus. There are two groups of shellfish of importance in human food, the mollusca and the arthropoda.The mollusca consists of bivalves (with a two-piece shell) such as oysters, mussels and scallops, and univalves with a one-piece shell such as whelks, limpets and cockles.

The cephalpods, such as squid, cuttlefish and octopus also fall into the univalve category.

The arthropods of relevance to human nutrition comprise the crustacea, a group which includes lobster, prawns, shrimps, crayfish and crabs.

Home Site Map Nutrition Aspects References note: in the narrative which follows, and that on other pages, underlined words indicate a link which will take you directly to the referred source. Use the "back " command on your browser to return to the narrative.

The Fats and Oils page gives basic information about the chemical make up of fats, and details of  the various components of dietary fats.

The Omega-3 page goes into more detail on the structure and metabolism of the polyunsaturated fatty acids.

The Balance page deals with the concept of a balance between the two classes of polyunsaturates (omega-3 from fish, and omega-6 from vegetables) and the health consequences of an imbalance.

The health consequences are discussed generally, and on separate pages more specifically in terms of the impact on various parts of the body, such as the heart and circulation, the brain and eyes, the joints, the skin, the digestive system etc.

        The narrative in these pages contains details of the original scientific publications which are used as the basis for the comments made. These are the references. By clicking on   a reference, you go directly to that reference, and can read more details of the work it reports. To get back to the place in the narrative that you left to go to the reference, click on your right mouse button, and select "back".

Site Map Nutrition Aspects References