Obesity strikes Salmon population

Salmon is rich in essential fatty acids, in particular the Omega-3 family of fatty acids. The description 'essential' means that the body cannot synthesise or can only synthesise limited amounts of the substance in question.

The long-chain fatty acids in the Omega-3 family include the parent alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. Oil-rich fish and supplements such as fish oil and cod liver oil are the richest and most readily available dietary sources of Omega-3.

The Omega-3 family of fatty acids has long been known to have positive health effects. Among other things, it is known to decrease triglyceride levels in the blood.

Farmed salmon have traditionally been fed, at least in part, on fish meal made from fast-growing, short-lived, oily, foraging fish species that are not generally used for human consumption. However, there is currently a short-fall in this fishery. In addition, pollutants such as dioxins become more concentrated as one moves up the food chain. Top predators such as salmon may end up with unhealthy levels. Feeding farmed salmon with fish meal may encourage this process.

These factors together with the fact that catching fish to feed fish is not especially environmentally friendly has led to efforts to find a land-based replacement for the fish meal component of the farmed salmon diet. The land-based feed uses vegetable oil instead of fish oil in the meal.

The proverb "you are what you eat" is well known and holds true for salmon as well as for us. Fish that have had vegetarian feed will have lower levels of the valuable Omega-3 fatty acids EPA and DHA. While some plant oils have been shown to have positive health effects due to their Omega-3 contents, fish oils have been shown to be more effective.

Studies in animal models have shown that fish protein alone can have a positive effect on lipid levels in the blood of rats. Clinical studies have also been undertaken in people comparing diets involving fish protein, salmon and fish oil. The results are now being analysed.