Question:
How do farmed salmon get their pink flesh? Do the producers add colouring to their diet? Also, as salmon in the wild make their omega oils from eating other sea creatures, how can farmed salmon make the same quality and quantity of omega 3 from eating a pellet containing mainly vegetable and animal oils, grains and land animals?
Answer:
A red-hued carotenoid called astaxanthin is the key to salmon’s orange-apricot-coloured flesh. It comes from the same family of highly pigmented antioxidants that make carrots orange. As they grow, wild king salmon eat an ocean-sized buffet of krill, pilchards, anchovies and other fish, many of which contain astaxanthin. This contributes to the orange-hued flesh. But how do farmed salmon get their brightly coloured flesh?
The Chinook (king) salmon, a native of the northern Pacific Ocean, is the only salmon species commercially farmed here. But it is not the only salmon to have a reddish hue induced by astaxanthin. The tinned pink Pacific salmon found on supermarket shelves also has a pale pink hue. This is because they also feed on shrimp and krill, which contain astaxanthin, thanks to their diet of microalgae, yeast and bacteria, which synthesise astaxanthin. Other sea life, such as shrimps, lobsters and crayfish, also have astaxanthin to thank for their reddish hues.
Researchers have been interested in astaxanthin because of its significant antioxidant and anti-inflammatory properties. They are focused on finding natural compounds that display therapeutic effects against chronic diseases.
A 2022 review in the journal Molecules, for example, highlighted the work investigating the carotenoid’s potential effects on ageing, particularly in preventing cognitive disorders in older people and maintaining general brain health.
Although the evidence is not yet definitive, that has not stopped manufacturers marketing supplements to keen consumers.
But while wild salmon get their astaxanthin, other micronutrients and energy from a varied diet of krill and other seafood, farmed salmon has a pellet-based diet. These pellets are designed to replicate the wild salmon’s diet from a macro- and micronutrient level, which includes the long-chain omega-3 fats needed for health. They contain fishmeal and fish oil, vegetable oils, poultry meal, other meat meal, wheat and a range of micronutrients, including astaxanthin, which is synthesised chemically rather than derived from natural seafood sources.
Importantly, the amount of long-chain omega-3 fats in the fillet is strongly influenced by the salmon’s diet, so farmed fish must be fed sufficient quantities of long-chain omega-3 fats for their flesh to become rich sources. Omega-3 fats are valuable for human health, as research suggests they may help raise HDL (good) cholesterol levels and lower blood pressure, among other things.
In the 1990s, feed for farmed salmon was made up of 83% fishmeal and fish oil, but in recent decades that has more than halved. Importantly, though, there is only so far salmon farmers can reduce the proportion of fishmeal/oil, as they must ensure the health and wellbeing of the fish are balanced against goals of sustainability (from the perspective of global fish resources) and economic viability.
So, from a human nutrition and wellbeing perspective, rather than popping an astaxanthin pill and an omega-3 supplement, eat whole foods such as fish and you’ll enjoy a balanced array of valuable macro- and micronutrients. Fresh salmon has a higher concentration of astaxanthin and omega-3 fats, but tinned salmon also contains both and may offer a more cost-effective and convenient option.
Whatever your personal choice – whether that is farmed salmon, tinned salmon, or freshly caught fish of another variety – enjoy the plethora of antioxidants, healthy omega-3 fats, vitamin D, selenium and protein that fish provide in our diet.
