Fish farms? Maybe we should call them fat farms

Senior Biologist and Certified Fisheries Scientist
Fisheries Technology Associates, Inc.

In 1986, Dr. Bill Lands wrote a book entitled Fish and Human Health. It wasn’t the first book written on the subject, nor is it today the best known. But it coincided here in the U.S. with a growing understanding that we might be smart to increase our consumption of fish as compared to other kinds of protein such as beef. Fish nutritionists also knew that aquacultured species must consume feed that contained certain minimum amounts and types of fats to maintain fish health. Fortunately, that also means that the end consumers (us) also benefit from this treasure trove of "thoughtfully" packaged fats and other nutrients.

Without getting too bogged down, let’s briefly cover some basic human nutrition. We eat three basic types of fats: saturated, monounsaturated, and polyunsaturated. Unless you’ve been marooned on Mars for 30 years, you’ve heard of the dreaded saturated variety. These fats have no double bonds in their chemical structure and, hence, are termed saturated. Monounsaturated fats, such as those found in olive oil and nuts, display one double bond in their chemical structure. Finally, polyunsaturated fats contain multiple double bonds in their chemical structure. The terms we often hear—omega-3 and omega-6 polyunsaturated fats—refer to the position of these double bonds within the structure.

Nutritional anthropologists and our genetics tell us that for optimum health we should consume one part saturated fats, to two parts monounsaturated fats, to one part polyunsaturated fats. Of the polyunsaturated fats, we should consume two parts omega-6 to one part omega-3 fats. According to my math, that means we should consume six times more monounsaturated fats as compared to omega-3 fats.

My point here is simple: there is no debate that omega-3 polyunsaturated fats are beneficial and essential to human health, particularly with regard to the heart and vascular system. At the same time we have heard little about the role of monounsaturated fats in optimizing human health, or for that matter their content in aquacultured species. Medical researchers have discovered that monounsaturated fats help lower our LDL ("bad") cholesterol levels.

According to the USDA Nutrient Data Laboratory, a 100-gram catfish fillet, for example, contains 1.77 grams of saturated fats, 3.59 grams of monounsaturated fats, and 1.57 grams of polyunsaturated fats. Whether by design or not, these amounts fit the recommendations quite closely. Catfish fall a bit short with regard to omega-3’s—less than 0.5 grams. A similar-sized trout fillet contains 1.55 grams of saturated, 1.54 grams of monounsaturated, and 1.80 grams of polyunsaturated fats, including at least 0.73 grams of omega-3’s—a better performance in omega-3 than catfish, but lacking in the monounsaturated category (fish tend to preferentially burn these for energy).

As you can see our fish are nutritionally imperfect in different ways. Aquaculture nutritionists and diet formulators are making great progress in developing diets and strategies for feeding those diets that make the best nutritional sense for the fish and the customers who eat them, and the best economic sense for growers who raise them. After all, what good are healthy fish and customers if we as producers can’t make a profit?

In an ideal world, the products we produce would conform to the perfect fat ratios I described above. The reality is that fish feed ingredients such as fish oil (high in omega-3’s) are expensive and become more so every day. At the same time, we must produce high-quality species at a reasonable cost. An encouraging answer to this dilemma may be at hand.

New salmon research indicates that fish may be fed less-expensive plant oils (omega-6 polyunsaturated fats) until just before the fish go to market. A much shorter "finishing" period, during which the fish are fed a diet high in omega-3’s, brings omega-3 levels back up to optimal levels. This looks to me like a win/win situation—growers minimize their costs of production and the customers eat a great-tasting and healthy product.

Without a doubt, fish nutritionists and feed manufacturers will continue to enable growers to enhance the quality and value of their products to customers, and keep a lid on feed costs in the process. Balancing fats to best meet the nutritional needs of people (including monounsaturated fats!) is just one of many future steps to improve the quality and image of aquacultured products.

As aquaculturists (unlike commercial fishermen), we are in the enviable position to tailor our products to best meet the nutritional requirements of our customers. The composition of our fish changes with their diet. Have you ever heard of nutraceuticals? They’re all the rage in the marketing community. These are value-added foods—designer foods, if you will—with specific health-promoting or remedial properties. Think about it. Aquacultured foods are nutraceuticals. Just one more reason to buy farmed over wild-caught species.