Masago is a type of fish roe—the fully developed eggs of certain fish species—and is a popular ingredient in certain cultural cuisines.
What is Masago?
Masago is a popular sushi ingredient, often used as a garnish or topping, made from the roe of the capelin fish, which can be found in the Arctic, Pacific and Atlantic Oceans, primarily in colder areas. Capelin are a type of smelt fish, and they are an important part of the food chain in their respective regions. The fish themselves are not a normal nutritional staple, and they are often processed for their oil or as other food ingredients, but a significant amount of the capelin are harvested for their eggs, as per a study published 2007 in the Woodhead Publishing Series in Food Science, Technology and Nutrition. 
Fish eggs have been traditionally eaten in many cultures due to their high nutrient density, and masago is most commonly seen on the outside of sushi rolls. While masago is typically a pale yellow in color, these fish eggs are often dyed brighter colors to be more visually appealing on the plate, or to mimic more expensive varieties of fish roe. Aside from decorating the outside of sushi rolls, these fish eggs are also mixed into various sauces and side dishes to add some extra crunch. 
There are many different types of fish eggs, ranging from beluga sturgeon and carp to salmon and capelin, and while there are variations in nutritional density, most types of roe share a similar nutritional profile. Capelin contains a good amount of vitamin B-12, more than 50% of your daily requirement in a single tablespoon, as well as moderate amounts of magnesium, iron, selenium, vitamin D, phosphorous, and sodium, ranging between 5-10% of the recommended daily intake. Masago also contains omega-3 fatty acids, the “good” kind of fat with a number of health benefits. In a tablespoon serving, masago has roughly 40 calories, 4 grams of protein and 3 grams of fat.
With its dense nutrient profile, masago has a number of health benefits, including protecting heart health, preventing weight gain, lowering oxidative stress, and boosting the immune system, among others.
- Heart Health: Numerous studies have found that adequate levels of omega-3 fatty acids are beneficial for heart health, including lowering your risk of coronary artery disease, by lowering blood lipids, according to a study published in Omega-3 Fatty Acids and Health. Additionally, the concentration of omega-6 fatty acids (“bad” fats) is remarkably low in fish roe, which further protects cardiovascular health. 
- Immune System: Selenium is a trace mineral that is often overlooked, but it is found in good quantities in masago and can help to improve the functioning and responsiveness of the immune system, as found in a study published in Immunology Today by Dr. Roderick McKenzie. 
- Weight Gain: Masago is a dense source of protein, which is an excellent source of fuel for the body. It is also ideal for preventing overeating, as protein is highly filling, so it can help to manage weight gain, according to a study found in The American Journal of Clinical Nutrition. Additionally, fish roe is very low in carbohydrates and calories, making it a nutrient-dense ingredient for those wanting to watch their weight. 
- Metabolism: Vitamin B-12 is found in very high levels in masago, which can help to regulate the metabolism, as maintaining proper levels of this vitamin is essential for energy production.
- Cognition: Research has found that high levels of selenium in the bloodstream are associated with a lower risk of cognitive decline and neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. 
- Fatigue and Depression: Vitamin D deficiency often affects those who live in areas without high levels of sunlight, and the symptoms include depression, fatigue, or trouble sleeping. Masago is a natural source of vitamin D for those who may need it! 
How to Eat?
Masago is traditionally found on the outside of sushi rolls, both for flavor, texture, and decoration. However, this fish roe can also be eaten plain, by the spoonful, or mixed into other sauces, such as wasabi or soy sauce. It is also a great topping for bagels, mixed into scrambled eggs, or tossed onto a salad. Despite being a fish egg, it can function very much like a nutrient-dense grain, and its mild flavor makes it versatile in many different applications.
Let’s take a look at the potential side effects of masago below.
- Allergy: There are no inherent side effects of masago, but allergens to fish roe are somewhat common, and there is a certain protein in masago (vitellogenin) that is a known allergen. Other gastrointestinal or dermal allergic reactions have also been reported. 
- Sodium: Masago also contains a good amount of sodium, which is linked to high blood pressure and other negative health effects when consumed in excess. Additionally, this fish roe is often added to other food that is already salty (i.e., soy sauce), so be sure to moderate your consumption.  
- Unhealthy Ingredients: Finally, some masago manufacturers and farmers will mix this popular product with high fructose corn syrup or other unwanted ingredients that can reduce the overall nutritional value. If buying masago in larger quantities, be sure to only buy from reputable farms or distributors. 
What is Masago Sauce?
Masago sauce is a general term for any combination of masago with other condiments, either to create a textured topping or a consistent paste. Masago sauce may contain any number of common ingredients—wasabi, soy sauce, mustard, mayonnaise, spices, lemon juice, green onion, and so many more. The key ingredient, of course, is the masago itself.
What is Masago Sushi?
Masago sushi is a designation of sushi based on the type of fish roe it is coated or topped with—the roe from the capelin fish. As mentioned above, the roe of capelin fish is often chosen due to its availability and lower price, in comparison to many other types of fish roe. Some of the most popular types of fish roe on sushi include ikura (salmon roe), uni (sea urchin roe), masago (capelin roe), and tobiko (flying fish roe). There is also caviar, which is considered the finest fish roe, and comes from beluga sturgeon. 
Tobiko vs Masago
Tobiko and masago are both fish roe that are popularly found as toppings for sushi, but they are notably different in certain ways.
- Tobiko comes from flying fish and is slightly larger and crunchier than the roe from capelin fish.
- Additionally, tobiko naturally has a bright red color, whereas masago is naturally a pale yellow, and is typically dyed to appear more vibrant.
- Tobiko is more highly sought after in the kitchen, as it has more sweetness and more versatility in sushi and sauces, but it is also the more expensive option of the two.