The healthy Omega-3 fatty acids are essential in human diets, especially when it comes to infant development and reducing cognitive decline in adults.
Two particular Omega-3 fatty acids -- abbreviated EPA and DHA -- are the two fatty acids that are both essential and limited in supply. Other fatty acids are readily available through plants.
"When we looked at how EPA and DHA are produced and consumed, in humans and in the ocean, we found that 70 per cent of the world's population doesn't get what they really need. That can have far-reaching health consequences," said Helen Hamilton from Norwegian University of Science and Technology and first author of the paper published in the academic journal Nature Food.
The world's fisheries are under pressure, with an estimated 63 per cent of all fish stocks considered exploited and in need of rebuilding.
That makes it unlikely that people can catch enough fish to provide their dietary needs for EPA and DHA.
"We can't take any more fish out of the ocean. That means we really need to optimize what we do have or find new, novel sources. We need to look at how EPA and DHA are produced and consumed by humans and in the ocean," lamented Hamilton.
To arrive at their results, the researchers collected data from the UN's Food and Agriculture Organization and the International Marine Ingredients Organization, along with published research articles and reports.
The data was fed into a model called a multi-layer material flow analysis framework.
This allowed Hamilton and her colleagues to estimate the amount of available omega-3 fatty acids, and how and where they are consumed.
The researchers suggest that better fisheries management, such as limiting catches and modifying fishing gear to cut the catch of unwanted fish, as ways to boost fish stocks.
Another marine source of EPA and DHA is krill, currently harvested from Antarctic waters.
"Increasing krill catch for use as feed could substantially increase the EPA/DHA supply," the authors wrote.
But catching krill from the Antarctic is both costly and challenging because of the sheer distance from Antarctic waters to markets.
Fish farming can help, but many farmed fish, including salmon, need fish feed that includes fish meal and fish oil.
"But too little EPA and DHA in fish feed can cause health problems in farmed fish and also reduce the amount of omega-3 fatty acids they contain," said the researchers.
Hamilton and her colleagues suggest that aquaculture can make strategic use of fish oils in fish feed by feeding these essential compounds to farmed fish at key life stages, especially right before the fish will be slaughtered for consumption.
People rarely eat all of a fish, yet these leftover by-products, such as innards and heads, also contain omega-3 fatty acids.
"Asia, far more than elsewhere in the world, is where there's most to be gained by collecting fish by-products for use," she said.
The researchers observed that EPA and DHA can be produced by both natural and genetically modified microalgae, as well as microbacteria and plants.
But that will also require a scale-up in production and changes in cultural acceptance, particularly in Europe, where current regulations limit use of genetically-modified organisms, the authors wrote.