Fish diets lessen chance of coronary disease

Press, 16 September 1987, Page 7

Fish diets lessen chance of coronary disease

PA Palmerston North Eating one or two fish meals a week could be a big factor in preventing coronary heart disease, says D.S.I.R. scientist, Mr Peter Vlieg. With a colleague, Denis Body, Mr Vlieg has spent the last 18 months determining the quantities of omega 3 fatty acids in more than 80 species of New Zealand fish, shellfish and fish roe.

Some species have dramatically higher levels of these acids, and when absorbed into the bloodstream, coagulation and adhesion of the blood to arterial walls are both lessened, thereby improving circulation and lessening heart disease risk, Mr Vlieg said. Omega 3 fatty acids are produced only by plankton, and remain in the food chain until eaten by man.

Greenland Eskimos eat fish, sea-blubber and sea birds, and tests have shown the bleeding time (before coagulation occurs) .of these people is remarkably longer than races of predominantly meat-eaters, Mr Vlieg said.

"Yet if these Eskimos go to Denmark and eat

steak and chips, they suffer the same rate of heart disease as the Danes,” he said.

Another study in the Netherlands covered 800 middle-aged couples, surveyed in two stages, 20 years apart. Deaths from coronary heart disease were 50 per cent lower among those eating at least 30 grams of fish a day. “We know that the prosta-glandin metabolism in man is affected by even a moderate fish diet — what is not known is how often fish should be eaten and the interaction with other factors such as smoking and exercise.” Fish fats consist of triglycerides, polarlipids and waxesters, which range in fatty acid content from 90 to 50 per cent. Two kinds of fatty acids affect the prosta-glandin metabolism in humans, with the marine variety (omega 3) forming double bonds in the carbon chain much closer to the tail of the molecule than those from plants and red meat animals (omega 6). Cheaper fish cuts tend to have a higher omega 3 fatty acid content — kahawhai, silver warehou, tuna, spiny dogfish, eels

and blue mackerel are highest, with the head and skeleton having the highest concentrations, Mr Vlieg said. Making soup from the bones and head of these species could therefore be a cheaper alternative for adding omega 3 fatty acids to a diet than buying more exclusive fillets such as snapper, he said. Using fish-oil capsules to supplement a diet may not be a good idea because these are often produced from the offal of the fish and therefore contain accumulated toxins from the liver, he said.

These supplements also contain high concentrations of vitamins A and D, which can also be harmful in big doses. "It is also important to remember that the beneficial effects were noted where people were eating fish instead of red meat — eating both red meat and fish oil capsules would cancel the advantages out.” . Mr Vlieg said that under the new user-pays

philosophy of research funding, no companies have come forward to fund continued investigations into omega 3 fatty acids.

His own research programme is winding down because of lack of funds.