Fish and nutrition – not all fish are created equal

Stephen Hall -

Drying Omena, Lake Victoria. Photo credit Patrick Dugan

“The idea that fish is a healthy diet choice is widespread, but fish differ in the benefits they offer, with implications for how we help the malnourished.”

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It might surprise you to learn that fish are more similar to fruit and vegetables than they are to poultry, cattle, or any of the other animals we eat. At least, they are if you think about the variety of shapes and sizes that fish and fruits and vegetables come in. As foods though, the more important similarity is that these various types differ widely in the nutrition they offer. So as with fruit and vegetables, while admonitions to eat more fish are often heard, exactly what kind of fish you eat matters – especially if you are malnourished.

But if you are poor and hungry and live in the tropics, there is a rule of thumb – eat smaller bodied fish because they are likely to be more nutritious. This is rather fortunate given the fact that it is usually these small fish that the millions of poor living near the worlds rivers and lakes and coasts eat. It is common in Africa and Asia, for example, to see piles of small dried fish for sale. These are added to soups and stews and provide essential nutrients that help provide the balanced diet that we all need.

It is a worrying fact though that most of these fish are caught from the wild and we have pretty much reached the limits of what nature can provide without help. Yet, as populations, wealth and urbanization increase so will the demand and need for fish, so we need to find more.

One option is of course, aquaculture. But right now aquaculture grows large bodied fish species, most of which do not have the nutritional profile of their smaller brethren. For developing countries, fish such as carps and tilapias are an important source of low fat, high quality animal protein and a viable and affordable alternative to meat for many poor consumers. And although eating them helps absorb nutrients from other foods, like most other meats they do less than smaller fish to help tackle the hidden hunger of micro-nutrient deficiency that affects so many people.

Large bodied species are also not so well suited to needs of the very poor. First, these

people cannot afford to buy large portions. Second, the distribution among the family of the flesh from a large fish often favors the adult males and male children, so women, younger children and especially girls miss out. In contrast, the small fish mixed into a stew are usually more evenly distributed.

So why not grow these smaller more nutritious fish? At local scales this is certainly a viable option. In Bangladesh, for example, farmers in several areas are seeding their ponds with small fish, to grow and reproduce naturally while feeding and growing larger fish species for sale. The smaller more nutritious species are then used to feed local families.

Expanding this idea, one can see how one might link these farmers into local supply chains to provide fish for school feeding programs or self-help groups that provide food to vulnerable people such as pregnant or lactating women. Researchers estimate that producing only 10kg of small nutrient dense fish per year in each of the 4 million ponds in Bangladesh can meet the annual recommended intake of Vitamin A for over 6 million children.

Of course, one could also consider encouraging larger-scale production facilities for small fish to feed into regional trade, but the economic viability of this approach is much less certain and needs careful analysis before investment could be justified.

Another way of fighting hidden hunger of course is to provide people with nutritional supplements or fortified foods. For plants there has been considerable effort put into these approaches and some notable successes. Most of us are familiar with supplementary iodine in iodized salt, and fish powders are now being examined as promising supplement. You could even argue that the fish sauces that are so widespread in Asia represent an indigenous food supplement.

But while supplementation has an important place in the armoury, it is a never ending business that relies on aid. In contrast fortified crops, such as the orange fleshed sweet potato bred with enhanced levels of vitamin D, offer the prospect of systemic improvements in the nutritional content of food.

For larger bodied fish species also, biofortification offers a means for overcoming the current lack of micro-nutrients. And because, unlike many plants, fish flesh does not contain anti-nutrients, chemicals that limit uptake of nutrients by humans, bio-fortified animal products are especially appealing. Moreover, achieving this is probably less technically demanding than improving crops because it can be done by manipulating feeds. The adage “you are what you eat” certainly applies for fish, and enriching fish feeds to enhance the fish flesh is a very viable option. We are already seeing this with other animal products – the omega 3 enriched egg now appears on many supermarket shelves.

As with most problems, there is no single solution to the scourge of malnutrition. Instead, we need a portfolio of research to make the most of what fish have to offer, and this requires work in three areas.

First, we need to work to increase sustainable access to, and consumption of, small

nutrient dense fish for vulnerable groups, such as pregnant or lactating women, and children. That means working out how to make the most of the fish that are available, either through direct consumption or through food supplementation products and programs, and how to grow and supply more of these fish through aquaculture.

Second, we need to support the aquaculture sector to increase the availability and affordability of the larger bodied fish species (tilapias, carps, catfishes) for poor consumers. This will help ensure the adequate high quality protein intakes that are essential for development.

Finally, we need to explore options for improving the nutritional profile of these larger fish so that they make an even bigger contribution to those who eat them.

If we invest in these three areas, we will have made great strides towards ensuring that fish fulfill their potential to tackle the scourge of hunger and malnutrition. And that’s got to be worth the effort.

Author
Stephen Hall

Stephen Hall

Stephen Hall's previous leadership roles include CEO of the Australian Institute of Marine Science (AIMS) and Professor of Marine Biology at Flinders University, Australia. Stephen has served on several international advisory panels and, in 2010, was a member of a global team overseeing the reform of the Consultative Group for International Agricultural Research (CGIAR). Recognized as a leading scientist in his field, he has contributed more than 80 scientific publications on fisheries ecology and environmental issues as well as a highly cited book on the environmental effects of fishing. In 2004, Stephen was awarded a Pew Fellowship in Marine Conservation and he continues to investigate and write on the roles and potential of fisheries and aquaculture for supporting international development objectives. In 2005, he was awarded the Australian Public Service Medal for leadership of AIMS. Stephen holds a Ph.D. in Marine Ecology from St. Andrews University and a B.S. in Marine Biology and Biochemistry from University of Wales, Bangor.

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