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Seafood & Health

The Fishmonger’s Company has been involved in ensuring safe seafood for over 400 years. Its recent participation in the healthy eating debate began when a group of leading researchers was asked to clarify the cholesterol issue and in January 2009 the Fishmongers’ Company hosted a ground-breaking conference on the health benefits of seafood. This summary outlines some of the key issues.

Prof. Tim Lang, Chairman, opened the conference by emphasising the crucial role fisheries play in the current debates over healthy eating and sustainability. The dilemma is that on one hand we are told to eat fish for brain and cardio-vascular health, while on the other we are told that fish stocks are running out and there are issues of pollution. His response was to ask, as an island surrounded by sea with large tides, why are we not massively increasing our mussel production and investing in ways of increasing consumption of seafoods which we can grow in sustainable ways?

The benefits of omega-3 fatty acids (EPA & DHA) in the diet

The conference was addressed by a number of leading international speakers. Among the key messages, Prof. Michael Crawford, of the Institute of Brain Health & Human Nutrition at London Metropolitan University, emphasised that human beings evolved on a diet rich in marine omega-3 fatty acids and these remain essential for healthy brain, nerve and eye development. But today the global requirement for these omega-3s can only be provided if fish and shellfish production can be doubled, sustainably. The cost to society from mental ill-health related to omega-3 deficiency is thought to represent 25% of health spending in the EU alone, outweighing the costs associated with heart disease and cancer combined. Eating roughly 100g of seafood a day (about five portions a week) gives a healthy intake of omega-3 fatty acids.

Prof. William Lands from Maryland followed by challenging the common presumption that heart disease is linked primarily to elevated cholesterol in the Western diet. In fact evidence suggests it is most commonly linked to omega-3 deficiency. Studies have shown that populations who consume a lot of seafood have very low levels of heart disease and little or no link with cholesterol. Prof. Lands noted that when trying to reduce saturated fat consumption, people need to be careful to avoid too much omega-6 in their diet which is derived from sunflower oil, corn oil and soy oil - all ubiquitous in processed foods and animal feeds. Opting for more seafood avoids this imbalance and boosts omega-3 levels in the body.

Three medical specialists, Prof. Philip Calder, Dr. David Levy and Dr. Tom Gilhooly all confirmed the importance of fish oil in the treatment of heart disease, illustrating this with the results of many major international studies.

The ‘cholesterol myth’

Many people believe they should not eat prawns because they contain cholesterol. However, it has been acknowledged for over 10 years that eating foods which contain ready made cholesterol, called dietry cholesterol, does not raise blood cholesterol. A recently completed trial in which people were given a diet high in prawns to investigate the effect on cholesterol was described by Prof. Bruce Griffin. The results of the study revealed there was no effect on peoples’ cholesterol level from eating 225g – about two portions - of prawns per day. These results have provided firm evidence to dispel the old ‘cholesterol myth’.

Obesity and seafood

Obesity is a major health issue throughout the Western world. A new approach being investigated is the ability of certain foods to satisfy appetite at lower levels of calorie intake. There is evidence that seafood scores well in this attribute, though at present the studies have only been done on whitefish, such as cod and ling. Dr. Anna Karin Lindroos, from the Medical Research Council Human Nutrition Laboratory in Cambridge, described the studies to date and the need for further research in this important emerging area.

Vitamins, minerals and seafood

Prof. Barbara Demeneix, from Paris and Sarah Keogh, a nutrition consultant from Dublin discussed the role that seafood can play in avoiding iodine and selenium deficiency, and the increasing evidence that people should be taking more vitamin D, either from diet (mainly in oily fish) or failing that from vitamin D supplements.

Conference Conclusions

The combined message from all these presentations on recent research was that regular consumption of seafood is unquestionably good for the health and that most people in the Western World need to choose to include more seafood in their diet. They will benefit, not just from the omega-3 and vitamin content, but from the reduction in calories, fat and omega-6 – basic but fundamental health influences.

Recent Developments

In  October 2010 the European Food Safety Authority (EFSA) published the Opinion of their Scientific Panel on the basis for health claims for the long chain ‘marine’ omega-3 fatty acids EPA and DHA, recognising their benefits in maintaining normal cardiac function, normal blood pressure and triglyceride levels -  all important factors in cardio-vascular health. (See: http://www.efsa.europa.eu/en/scdocs/scdoc/1796.htm)

Since they achieve all this without lowering blood cholesterol it is clear that cholesterol-lowering is not the only way to protect the heart. EPA and DHA protect the heart both in a direct way and indirectly, by stabilising normal blood pressure and triglycerides. 

In December 2010 an important paper was published in the British Journal of Nutrition. This showed that many earlier studies which related heart benefits to cholesterol-lowering by polyunsaturated fats had actually used both omega-3 and omega-6 types. When these were separated out, it appeared that, while the omega-6 fats do lower cholesterol, the benefits to heart health could be accounted for by the omega-3 content.

(See C. Ramsden et al 2010, n-6 Fatty acid-specific and mixed polyunsaturated dietary interventions have different effects on CHD risk: a meta-analysis of randomised control trials. British Journal of Nutrition (2010), 104, 1586-1600.)

Dr. Clive Askew
Fisheries Consultant