Crab shell extract could nip obesity

Irish scientists are experimenting on the use of extracts from crab and shrimp shells as a treatment for obesity

CRABS and shrimps may not realise it quite yet, but their protective cover may become as valuable as their meat on world seafood markets. That’s because a compound in their shells, chitosan, may help to tackle the developed world’s major illness – obesity.

International research on the compound has already indicated that it could help to reduce food intake.

Claims that chitosan “fat trappers” sold on the US market could be used to modify the effects of unrestricted food intake were challenged several years ago by University of California researchers.

However, animal trials carried out by Dr Bahar Bojul of University College, Dublin, as part of a national functional foods research programme, suggests that there is potential.

Chitosan is a sugar chain or “linear polysaccharide”, comprising D-glucosamine and N-acetyl-D-glucosamine. It can disrupt the body’s natural mechanisms, which balance the amount of food we eat with what we actually need, the UCD research suggests.

The trials show that chitosan can interfere with the uptake of fats or lipids into cell membranes and block the body’s hunger response. If this can be proven to have the same effect on humans, it could help tackle obesity, which is said to be a factor in up to 2,000 deaths annually in Ireland.

The research was presented to fellow scientists at the Teagasc Ashtown Food Research Centre in Dublin last week, as part of the NutraMara marine functional foods research project.

Up to 30 scientists attached to Teagasc’s Ashtown and Moorepark research centres, along with colleagues from UCD, University College Cork, NUI Galway Martin Ryan Institute, University of Limerick and University of Ulster are participating in the project.

Nutramara is funded by the Marine Institute and the Department of Agriculture, Fisheries and Food. It aims to tap the potential of functional foods – a “multi-billion super-foods market” in which Ireland could become a key player, according to the Marine Institute. It published a report on the opportunities for Irish seafood several years ago.

“Japan already has several product ranges on the shelves and research programmes are under way all over the world to create more,” says Dr John Joyce, of the Marine Institute.

“Our seas are a huge reservoir for bioactive compounds that can be incorporated into food additives which can be harnessed for human health,” says Dr Maria Hayes, Nutramara scientific project manager.

Ireland’s 501 species of seaweed have been talked about for years as having untapped potential – in contrast to Japan, where sea “vegetables”, as they are known, are cultivated for an enthusiastic domestic market.

Only a fraction of Ireland’s various species have been used commercially, but with little added value – although coastal communities have relied on the health benefits of carrageen moss (now widely available in health food shops) for centuries.

Dr Pádraigín Harnedy, of the University of Limerick, is researching seaweed for Nutramara as a source of “biofunctional peptides” – protein molecules that promote health by blocking certain harmful chemical pathways in the human body, such as the laying down of cholesterol in blood vessels.

“Irish seaweeds have great potential as a source of biofunctional peptides,” she says. “Red seaweeds contain the highest levels of protein, at almost 50 per cent per dry weight.”

Such compounds have a wide range of positive effects on human health, including killing harmful bacteria, lowering hypertension, assisting our immune systems and preventing thrombosis, she says.