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What are the Potential Risks and Benefits Associated with Consumption of Salmon Skin?

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.

Fat in Salmon

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.

Nutritional Benefits of Salmon Skin

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:

  • inhibit the activity of angiotensin I-converting enzyme (ACE) and by so doing lower risk of high blood pressure
  • decrease inflammation by preventing release of pro-inflammatory messaging molecules
  • decrease risk of type 2 diabetes by decreasing both inflammation and oxidative stress

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.

Potential Contaminants in Salmon Skin

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.

WHFoods Recommendations

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.

References

  • Arnesen JA and Gildberg A. Extraction and characterisation of gelatine from Atlantic salmon (Salmo salar) skin. Bioresource Technology, Volume 98, Issue 1, January 2007, pages 53-57.
  • Aursand M, Bleivik B, Rainuzzo JR, et al. (1994). Lipid distribution and composition of commercially farmed atlantic salmon (salmosalar). J. Sci. Food Agric., 64: 239—248. doi: 10.1002/jsfa.2740640214.
  • de Gelder S, Bakke MJ, Vos J, et al. The effect of dietary lipid composition on the intestinal uptake and tissue distribution of benzo[a]pyrene and phenanthrene in Atlantic salmon (Salmo salar). Comp Biochem Physiol C Toxicol Pharmacol. 2016 Jul-Aug;185-186:65-76.
  • Gribbestad IS, Aursand M, and Martinez I. High-resolution 1H magnetic resonance spectroscopy of whole fish, fillets and extracts of farmed Atlantic salmon (Salmo salar) for quality assessment and compositional analyses. Aquaculture, Volume 250, Issues 1—2, 14 November 2005, pages 445-457.
  • Gu RZ, Li CY, Liu WY, et al. Angiotensin I-converting enzyme inhibitory activity of low-molecular-weight peptides from Atlantic salmon (Salmo salar L.) skin. Food Research International, Volume 44, Issue 5, June 2011, pages 1536-1540.
  • Hsieh CH, Wang TY, Hung CC, et al. Improvement of glycemic control in streptozotocin-induced diabetic rats by Atlantic salmon skin gelatin hydrolysate as the dipeptidyl-peptidase IV inhibitor. Food Funct. 2015 Jun;6(6):1887-92. doi: 10.1039/c5fo00124b.
  • Jobling M and Johansen SJS. (2003), Fat distribution in Atlantic salmon Salmo salar L. in relation to body size and feeding regime. Aquaculture Research, 34: 311—316. doi: 10.1046/j.1365-2109.2003.00820.x
  • Lee JK, Jeon JK, and Byun HG. Antihypertensive effect of novel angiotensin I converting enzyme inhibitory peptide from chum salmon (Oncorhynchus keta) skin in spontaneously hypertensive rats. Journal of Functional Foods, 2014, 7, pages 381-389.
  • Li-Chan EC, Hunag SL, Jao CL, et al. Peptides derived from atlantic salmon skin gelatin as dipeptidyl-peptidase IV inhibitors. J Agric Food Chem. 2012 Feb 1;60(4):973-8.
  • Nanton DA, Vegusdal A, Rora AM, et al. Muscle lipid storage pattern, composition, and adipocyte distribution in different parts of Atlantic salmon (Salmo salar) fed fish oil and vegetable oil. Aquaculture. 2007 May 1;265(1):230-43.
  • Nolan JM, Beatty S, Meagher KA, et al. Verification of Meso-Zeaxanthin in Fish. Journal of food processing & technology. 2014;5(6):335-347. doi:10.4172/2157-7110.1000335.
  • Yu F and Huai ZX. Utilization of chum salmon (Oncorhynchus keta) skin gelatin hydrolysates to attenuate hydrogen peroxide-induced oxidative injury in rat hepatocyte BRL cell model. Journal of Aquatic Food Product Technology, 2015, 24, 7, pages 648-660.
  • Zhang X, Gandhi N, Bhavsar SP, et al. Effects of skin removal on contaminant levels in salmon and trout filets. Science of The Total Environment, Volume 443, 15 January 2013, Pages 218-225.
  • Zhang Z, Wang J, Ding Y, et al. Oral administration of marine collagen peptides from Chum Salmon skin enhances cutaneous wound healing and angiogenesis in rats. Journal of the Science of Food and Agriculture, 2011, 91, 12, pages 2173-2179.
  • Zhu CF, Peng HB, Liu GQ, et al. Beneficial effects of oligopeptides from marine salmon skin in a rat model of type 2 diabetes. Nutrition, Volume 26, Issue 10, October 2010, pages 1014-1020.

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