Although its ingredients – fish, vegetables, fruit and algae – are beneficial in themselves, the problem is in the proportions and the carbohydrates.

We often consider sushi a health food. After all, it has ingredients like fruits, vegetables, algae and its star component: blue fish. Based on current food consumption trends, a 45% of Spaniards consume it at least once a month.

While in Japan the most used is tuna, in Europe it is salmon. Both are a good source of protein, iodine, and vitamin D. They are also rich in healthy fats., that participate in the regulation of arterial pressure, in inflammatory processes and in blood clotting. Therefore, they help fight heart disease and stroke.

On the other hand, sushi usually contains fresh fruits or vegetables that contain significant amounts of fiber, minerals and vitamins, mainly vitamin C. To date, the fruit most used in its preparation is avocado, rich in vitamin E and monounsaturated fatty acids, effective against cardiovascular diseases.

To shape this Japanese snack, it is often used salary wants. It contains a high concentration of proteins, which can represent up to 44% of the dry matter. Its levels are comparable to those found in vegetables such as soy (40%).

Not all that glitters is gold

However, the sushi roll provides very little of these fish, fruits, vegetables and seaweed. In fact, its main component is pearl white rice, which has had most of its fiber, vitamins and minerals removed. In addition, it is usually prepared with sugar, so its intake could lead to a high consumption of easily assimilated sugars.

It is true that current studies suggest that part of the starch present in the rice used for sushi is resistant to the action of digestive enzymes. Therefore, it would provide fewer calories than, in principle, we might think.

When we cook the rice and cool it (about 4ºC), part of the starch forms a crystalline structure, very difficult to degrade by enzymes. In this way, it acts as a soluble fiber, with the health benefits that this entails. For example, it increases satiety and reduces blood sugar spikes.

The fact that the starch reaches the colon without being digested means that it can be used as a substrate by the bacteria of the intestinal flora, producing protection against colon cancer, among many other health effects.

Even so, let’s think about another of the condiments that usually dress sushi pieces: soy sauce, very rich in salt. Depending on the type chosen, a tablespoon can contain between 1 365 and 2 535 milligrams. This represents between 27.3 and 50.7% of the maximum daily amount recommended by the World Health Organization (WHO), about 5 grams, to reduce hypertension, cardiovascular disease or stroke.

In addition, many types of sushi are prepared with sauces that are high in fat, like spicy mayonnaise. Others are coated with tempura masses that are fried, so their energy value is considerable.

Variants of the Japanese snack

The sliced ​​raw fish, known as sashimi, is the healthiest type of sushi. Why? Because it doesn’t have rice.

For its part, nigiri, an elongated rice ball covered with an additional ingredient, usually a piece of fish or shellfish, is usually less caloric than maki (the famous roll). Again, because it contains less rice and does not have sauces.

The maki, is the version made with nori seaweed sheets, used to wrap the rice and the rest of the ingredients. It is one of the most caloric types of sushi, since it is usually accompanied by more rice and other dressings. Of course, as we said, it will depend on the rest of the ingredients.

The California roll, for example, with surimi, cucumber, avocado, sesame and mayonnaise, is one of the makis preferred by consumers. It is estimated that its caloric intake is about 349 kilocalories per piece. If we also consume it in tempura, battered with flour and fried, the amount could amount to about 632.

Another of the most popular, the Philadelphia roll, which in addition to salmon contains cheese, provides around 391 kilocalories. If we eliminate the cheese, its energy value drops to about 278.

To avoid that dressings and sauces can excessively increase the levels of salt and fat in a serving of sushi, it is advisable to only add a small quantity to enjoy the flavor, rather than generously dipping the piece.

Parasites, microorganisms and metals

Sushi is often considered a potentially dangerous food product, using raw seafood. These are susceptible to harboring parasites, bacteria and heavy metals.

The most common disease associated with sushi consumption is anisakiasis, a disease that is triggered when we ingest live anisakis larvae. It is a parasite that can cause digestive disorders and allergic reactions. Sometimes serious.

According to the Spanish Agency for Food Safety and Nutrition (AESAN), the best way to prevent it is freezing the fish for 5 days at -20 ºC. If the refrigerator does not reach that temperature, you should buy fish already frozen.

Contamination by pathogenic bacteria, such as Salmonella The Listeria monocytogenes, is another danger associated with sushi. The cause is the lack of heat treatment of fish and shellfish.

On the other hand, there are some studies that show that part of the fish that we use for the preparation of sushi has an excess of mercury. The truth is that bluefin tuna is one of the fish that concentrates the most mercury. However, only most vulnerable population groups, such as pregnant women and children, should restrict their consumption.

In addition, it is possible to substitute it for other fish: salmon, cod or sea bream, for example.

In short, if we take into account the nutritional composition of sushi, we can say that it is a healthy meal as long as it is not accompanied by an excess of sauces or tempuras. However, it is important that we use microbiologically safe ingredients for its preparation. Or, that we consume it in restaurants that guarantee good hygienic conditions. Thus, we will avoid possible food poisoning.

* Isabel Odriozola Serrano is pProfessor of Nutrition and Food Science at the University of Lleida.

** This article originally appeared on The Conversation.