Just How Healthy Is Salmon?

Salmon is good for you — that part we know.

“Fish is one of the few animal foods consistently linked to health benefits, and salmon is at the top of my list when I recommend fish to people,” said Dr. Dariush Mozaffarian, a distinguished professor and the director of the Food is Medicine Institute at Tufts University.

But choosing which type to eat for your health — sockeye or coho, wild or farmed — isn’t so obvious. Researchers have found that the nutritional value of salmon can vary depending on the species. And there is a consumer perception that farmed and wild-caught salmon differ in terms of their nutrients and levels of contaminants — beliefs that research partly supports.

From healthy fats to heavy metals, here are answers to all your salmon-related questions.

What’s so great about salmon?

Dr. Mozaffarian highlighted omega-3 fatty acids — specifically DHA and EPA — as one of salmon’s distinctive nutritional attributes. Salmon packs more DHA and EPA omega-3s than almost any other food, apart from other fatty fish such as herring and sardines.

Studies have consistently linked the consumption of omega-3 fatty acids from seafood to lower rates of stroke and heart disease. Research suggests these fatty acids reduce arterial stiffness, which is associated with high blood pressure, and they may also have anti-inflammatory effects that could be protective against obesity and Type-2 diabetes.

Dr. Mozaffarian also said that omega-3s are essential to early life brain development, and emerging evidence suggests that consuming them regularly may guard against age-related cognitive decline and neurodegenerative diseases, such as Alzheimer’s.

While the human body is able to make some DHA and EPA on its own, eating foods high in these omega-3s can help ensure the body and brain get what they need, he said. The American Heart Association recommends eating a 3-ounce serving of fish (particularly fatty fish, like salmon) at least twice a week.

While many supplements contain omega-3s, there’s evidence that getting these fats from seafood may be superior, perhaps because there are compounds in fish meat that help prevent omega-3s from breaking down during digestion.

In addition, experts say that salmon contains other nutrients, such as protein, selenium and iodide, that may support or augment the healthy effects of these fats. “The focus is usually on omega-3s, but it’s the whole package that makes salmon so healthy,” said Matthew Sprague, a lecturer in nutrition at the University of Stirling Institute of Aquaculture in the United Kingdom.

Is one type healthier than another?

“There are so many different options in the marketplace, it can be confusing,” said Stefanie Colombo, an associate professor and research chair in aquaculture nutrition at Dalhousie University in Canada.

In an attempt to clear up some of that confusion, Dr. Colombo examined the nutritional values of the types of salmon available to consumers. “The main finding of our work was that there’s not much difference between wild and farmed,” she said.

While wild sockeye and wild chinook — two of the most commonly sold species — were the most “nutrient dense,” her study also found that farmed Atlantic salmon only had slightly lower levels of omega-3s, proteins and other healthful nutrients. Wild Pacific pink salmon tended to have less of these nutrients than the other types, regardless if they were farmed or wild.

The nutritional figures in Dr. Colombo’s study were averages, however. Depending on factors such as the type of feed given to farmed salmon, or the time of year a wild salmon is caught, she said, the levels of healthy fats or other nutrients can differ from fish to fish.

Dr. Colombo added that “all the salmon we looked at was very nutritious.”

What about mercury and other contaminants? Dr. Colombo said her paper did find some differences among types: Farmed Atlantic salmon, for example, tended to have lower mercury levels than wild-caught varieties. However, all the samples contained levels of mercury far below international safety standards. “Even if you ate salmon every day, mercury is not something you should be concerned about,” she said.

The same can be said for polychlorinated biphenyls (PCBs) and other contaminants that sometimes turn up in seafood. Research has found that salmon, whether wild or farmed, does not contain harmful levels of these toxins. That’s partly because it doesn’t live long enough to absorb a lot of them, Dr. Mozaffarian said.

For those concerned about the ecological impact of their food choices, salmon comes with some baggage; both the overfishing of wild species and farming-related pollutants are ongoing concerns. But experts said that all types of salmon outperform most animal sources of protein, in terms of environmental footprint.

When buying salmon, Dr. Colombo recommended looking for label certifications from the Marine Stewardship Council (MSC) or Best Aquaculture Practices (BAP). “If the salmon is certified, that should give you more confidence it has been sustainably and ethically sourced,” she said.

Above all, the experts affirmed that all salmon is good for you, and agonizing over a choice isn’t necessary: “Assuming you like the flavor,” Dr. Mozaffarian said, “it’s really the perfect fish.”