By Avery Keatley
Unless you’ve been to Atka, Alaska, part of the archipelago sweeping across the Bering Sea, Steller sea lion liver probably hasn’t graced your plate or touched your tongue. Sea lion—the second most consumed “traditional” food of Alaska, next to reindeer—is especially prized for its nutritional benefits. A quarter-pound serving has fewer than 200 calories, about 25 grams of protein, and only 2 grams of carbs. (The North Beach Diet—can you see it coming?) But sea lion liver also contains the highest amount of an amino acid not listed in the nutrition facts: arginine.
Arginine is produced naturally in the body and absorbed through food. It aids in the process of nitric oxide creation. 1998 Nobel Laureate Dr. Louis Ignarro discovered, along with other researchers, some of the many benefits of nitric oxide in the body. Principally, he says that, “nitric oxide [NO] makes sure that all the organs in the body receive the normal amount of blood, and therefore the nutrients and oxygen that’s required,” for the body to function properly. Arginine is the substrate, or “biological precursor” to nitric oxide. Although there’s no recommended daily dose of arginine according to Mayo Clinic, it’s an amino acid your body depends on.
Now, before booking your flight to Atka, which will prove a nearly insurmountable challenge, you should know that your turkey club sandwich is also high in arginine. Spinach and turkey both have high levels of arginine, and so do crab, shrimp, and lobster. You can also buy arginine at nutrition supplement stores, although, like most supplements, that’s probably not necessary.
Arginine can produce a number of things, not all of them good. It can produce oxidative compounds, especially in people who are overweight or obese. These people produce more ADMA—asymmetric dimethylarginine—that inhibits the production of nitric oxide and can cause the production of oxidants. Oxidants are unstable compounds that can do damage to cells, proteins, and lung function when the body doesn’t have enough antioxidants. So all those antioxidant foods you’ve been eating? Well, these are some of what they’re combatting. (By the way, getting enough antioxidants doesn’t mean you have to guzzle açai juice by the gallon. About two slices of pineapple will give you more than the daily recommended dose for the antioxidant vitamin C.)
So what does this all mean? Well, think about nitric oxide for a minute. Dr. Fernando Holguin, an asthma and obesity specialist at the University of Pittsburgh says, “Nitric oxide is a gas that everybody produces…it has lots of activities in the brain, the vascular [system], the lungs. Arginine is one of those things that we’ve found that people with asthma have less [of.]” Less arginine means lower levels of nitric oxide in the airways, which means obese asthmatics are missing an important “messenger” chemical. Dr. Holguin has a hypothesis that might help them.
“The idea is that, one of the ways you can reverse this phenomenon is by giving back the substrate that generates nitric oxide.” Nitric oxide is generated from arginine, but giving patients arginine supplements might not produce the best effect. When arginine gets metabolized it becomes less effective in producing nitric oxide. Dr. Holguin’s potential solution is, presumably, much tastier than sea lion liver—it’s watermelon.
Citrulline is an amino acid found in watermelon and other foods, including cucumbers and cantaloupe. Citrulline is the substrate of arginine, but unlike arginine, it is metabolized in the kidneys as opposed to the liver and intestines. By bypassing the liver, citrulline becomes more effective in raising arginine levels. The hope is that by giving patients citrulline, they will increase their ratio of arginine to ADMA in the body, and override the inhibiting effect of ADMA on nitric oxide production.
Wait just a second before you dive face first, teeth gleaming, into that watermelon. To get the same amount of citrulline from a watermelon as Dr. Holguin is giving patients in his pilot study, you’d have to eat 12 cups (or 3.75 pounds) of watermelon every day. For a week. The citrulline they receive is in the more manageable form of an effervescent drink.
Dr. Holguin hopes that by supplementing these patients with citrulline, they will produce more nitric oxide and increase their lung function. “Because nitric oxide is involved in how well you airways function, the idea is that if you give [arginine] back, you may improve the respiratory health in obese folks.” Dr. Holguin cautions that, if there is a response to citrulline, it is most likely to help late onset, obsese asthmatics, with normal to low levels of nitric oxide. Returning citrulline to the body, though, might be the first step in that direction—no sea lion liver necessary.