Nutrition researcher: The human diet needs more shellfish

Published on
October 29, 2018

Numerous studies have shown that eating seafood is good for human health, but Professor Baukje de Roos, deputy director of the Rowett Institute at Scotland’s University of Aberdeen and an internationally recognized nutrition scientist, believes that shellfish are some of the most important contributors of essential nutrients and should be given a great place in the diet. 

Professor de Roos, who is currently researching the effects of farmed seafood on heart health and micronutrient status, updated delegates at the recent Association of Scottish Shellfish Growers conference in Oban, Scotland, on the major health benefits of seafood and outlined the important involvement of shellfish. 

Professor de Roos reminded her audience that omega-3 fatty acids help to protect against stroke and lower the risk of mortality from coronary heart disease, while vitamin D is essential for the growth and maintenance of healthy bones; and vitamin B12 is involved in the functioning of the nervous system, the formation of red blood cells, and in energy production.

“Micronutrients such as selenium, iodine, and zinc are also found in abundance in shellfish and all have important functions,” de Roos said.

Turning to Europe, she pointed out that different countries offer varying recommendations for overall seafood consumption, ranging from 125 grams per person per week in the Netherlands, to 450 grams in Norway. However, only in Spain and Scotland is the level surpassed, with Scotland’s consumption level almost double the recommended 375 grams per person. In most countries, seafood consumption falls well below recommended limits.

However, in all countries, it is the older generation who are the major seafood eaters, with teenagers of both sexes eating the least amount. This is a worrying trend that needs to be reversed, de Roos said, suggesting that young people might be lured into eating more seafood by interesting them in different and new kinds of dishes. 

Looking at the overall levels of omega-3s in fish and shellfish, she pointed out that oily fish such as mackerel, herring, and salmon, which come with the recommendation to eat one portion per week, contain levels between 1.1 and 2.4 grams per 100 grams of flesh. Mussels, oysters, and king scallop roe all fall within this range, while brown crab meat contains more than 3 grams per 100-gram portion. In addition, langoustine, lobster, and white crab meat all contain higher levels of omega-3s than white fish. 

The total percentage of fatty acids was found to be broadly similar whatever the season, whereas vitamin B12, selenium, zinc, and iodine can vary throughout the year.

“Oysters in particular are high in zinc and would be a good addition to the diet of anyone aware that they have a deficiency,” said de Roos. 

Two trace elements commonly found in shellfish, cadmium and lead, were also found in increased levels in humans following increased consumption of mussels, but these were well below hazardous levels, even with three portions per week. 

She outlined a study recently undertaken to establish the number of mussel meals needed per week in order to produce a physiologically meaningful change in nutrient status.

Eating three 85-gram portions per week for 12 weeks was found to be the most beneficial for health, raising omega-3 index levels to those similar to a group eating salmon regularly. It also increased folate levels. 

The population studied went from an index of less than two to 12 on a scale where a level of seven is the minimum needed to maintain good health and a score of eight or more is desirable. Levels can easily be detected with an at-home finger prick blood test.

“These results were largely due to increased seafood consumption, but there is also a genetic element that plays a part,” de Roos said. “However, the overall message is definitely one of ‘eat more shellfish.’”

She explained that shellfish has historically lost out on the omega-3 health claim message in marketing efforts and believes that this should be changed. 

According to the European Food Safety Authority, to claim that a product is a ‘source of’ a nutrient it should contain 15 percent of the recommended daily amount (RDA) in 100 grams, or 15 percent, of the amount they could reasonably be expected to consume.  

To make a “high in” nutrient claim, the product must contain 30 percent of the RDA in 100 grams, or 30 percent of the amount they could reasonably be expected to consume. For fish, this may need to be on a weekly basis.

“This means tht mussels, oysters, king scallops, crab, lobster and langoustine can all claim to be a ‘source of’ omega-3 fatty acids, and mussels, oysters, king scallop roe, and brown crab meat can claim to be ‘high in’ omega-3 fatty acids,” de Roes said. “If you add in claims for the vitamins and minerals as well, the marketing message will be really strong.”

Photo courtesy of the University of Aberdeen

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