At WHFoods, we recommend that you remove skin of salmon prior to cooking, unless you have a high level of confidence in the quality of the fish, including a reason to suspect low risk of contaminants. Because we get a good number of questions about the risks and benefits of the skin, we researched and drafted this article to provide you with more in-depth information.
Studies show a widely varying amount of total fat in salmon. This diversity in the amount of fat makes sense to us. The life cycle of salmon is complicated, and it would not make sense for these fish to contain the same amount of fat across all stages in their lives. For example, the total amount of fat in many species of salmon appears to peak just as they leave the ocean and begin their return to fresh water. This "peak fat" moment in their life cycle makes sense because their return to fresh water requires a lot of energy expenditure on their part, and fat deposits provide an efficient way to store potential energy. The fat content is also known to vary from species to species and from ocean to ocean.
The fat content of salmon skin is roughly double the fat content of salmon muscle. That said, the fat content of salmon muscle is also relatively high. In a 3-4 ounce serving size for salmon (our website example uses 4 ounces cooked and skinless salmon), we have never seen less than approximately 4-5 grams of total fat. While all of us would have room for that amount of fat in our daily meal plan, it is still a higher level than the amount of total fat found in 4 ounces of cooked cod, scallops, shrimp, or tuna. If we include skin in this 4-ounce serving of cooked salmon, the total fat content definitely increases. A high-side estimate here would be about 14-15 grams of total fat in a 4-ounce serving of cooked salmon that included the skin. A low-side estimate would be closer to 7-8 grams. So as you can see, there is a good bit of variability here. And since this variability depends on salmon species, salmon age, ocean location, and other factors, it can be difficult to pinpoint the exact amount of total fat that you are getting from inclusion of the salmon skin. There can also be differences in the amount of skin that actually remains when salmon is fileted to become "skinless." At a minimum, we believe that you are likely to be increasing the total fat content by at least 3 grams when you include the skin in a 4-ounce serving of cooked salmon. But you might also be increasing it by 10 grams or more depending on the exact circumstances.
As most people are aware, fatty fish can be an unusually concentrated source of specific omega-3 fats, including DHA (docosahexaenoic acid). Our 4-ounce website serving of cooked wild coho, for example, provides 750 milligrams of DHA. It also provides 1.32 grams of total omega-3s. If skin were left on this same 4-ounce serving of salmon, both its DHA content and its total omega-3 content might be doubled. So you can easily see the potential omega-3 benefits that might be possible with inclusion of the skin.
Virtually all foods contain at least some small amount of protein. Within this protein category are smaller protein components called peptides. The peptides found in salmon skin have been of growing interest to researchers because of their potential health benefits. Most of the studies to date have been conducted on animals only. Still, study results have been fairly consistent that reflect that the unique peptides found in the skin of salmon may:
Also present in salmon skin are unique forms of carotenoids, including meso-zeaxanthin. We know that this particular carotenoid plays a unique role in the central portion of the macula in the human eye. (The macula is itself positioned in the central portion of the retina at the back of the eye.) Researchers are not yet certain about the level of meso-zeaxanthin found in salmon skin and the level found in salmon muscle (or in other fish or plant foods). But salmon skin may turn out to be a uniquely concentrated source of this carotenoid nutrient.
In short, the list of potentially helpful nutrients in salmon skin is an impressive one, and if salmon skin could be consumed without increased risk of exposure to contaminants, it would usually make sense to do so from a strictly nutritional perspective.
Unfortunately, however, we also know that for many salmon species in many life circumstances, the skin can be a special source of contaminants. We've seen one study, for example, that examined levels of contaminants in salmon skin including: mercury (a heavy metal); α-chlordane (a pesticide); hexachlorobenzene (a chemical manufacturing by-product), mirex (an insecticide); octachlorosytrene (another chemical manufacturing by-product); polychlorinated biphenyls (PCBs) (chemicals with a wide variety of industrial uses, now largely banned worldwide); and dichlorodiphenyltrichloroethane, also known as DDT (an insecticide long banned for use within the U.S. but not banned worldwide).
Coho and Chinook salmon swimming in the Credit River in Ontario, Canada, were the species of salmon being analyzed in the study. With the exception of mercury, all of the contaminants listed above were found to be decreased by 17-37% by removal of the skin from salmon filets. And the authors of the study went on to recommend removal of salmon skin from these fish as a way to lower exposure to contaminants.
The results of this study were not surprising, given the nature of many persistent organic pollutants (POPs) in ocean waters. POPs are manmade organic chemical substances—usually fat-soluble—that do not quickly decompose and can remain in soil, air, and water in large amounts over the course of many decades. Since POPs are widely transported by ocean currents (and by air currents in the atmosphere as well), it is not surprising to find them being deposited in the fatty tissue of fish like salmon that are themselves naturally higher in fat and swim in ocean waters worldwide.
As described at the outset of this article, we recommend removal of salmon skin prior to cooking, unless you have a high level of confidence in the quality of the fish. Too many salmon are making their way through contaminated waters with too much exposure to fat--soluble contaminants that can get incorporated into the higher-fat skin tissue of the fish. However, not all salmon skin is high in contaminants, and in its non-contaminated form, the skin can be a source of unique nutrients including meso-zeaxanthin, health-supportive peptides, and omega-3s. Organizations like the Monterey Bay Aquarium Seafood Watch, National Resource Defense Council, the Environmental Working Group, and the Environmental Defense Fund have developed a variety of consumer-friendly resources to help U.S. consumers identify high-quality fish. If you want to include the skin in your consumption of salmon, you may find these websites helpful in selecting the lowest risk species from the least contaminated habitats.