Forget ham and cheese or egg mayo sandwiches, sushi is now a lunchtime staple with its dizzying array of omega-3-rich raw fish, seaweed and fresh and pickled vegetables. A veritable health powerhouse in neat packaging, you might think. But is it actually any good for us?

What does sushi contain?

Sushi typically refers to raw fish, such as salmon or tuna, and sushi rice that is wrapped in a sheet of dried seaweed called nori.

It may also be filled with slices of omelette or fresh crunchy vegetables (such as cucumber, avocado or pepper) and topped with salmon roe or sesame seeds.

Soy sauce, ponzu sauce, teriyaki sauce or sriracha mayonnaise are some common accompaniments, as are pickled ginger and wasabi paste.

What are the health benefits?

“Fish – especially oily fish – are one of our richest dietary sources of omega-3 fatty acids,” says Dr Sarah Brewer, a nutritionist and author.

Omega-3s are a type of fat that help keep the heart healthy. “They are commonly lacking in the diet but they are vital for health, promoting heart health and brain function and reducing inflammation,” says Kim Pearson, a nutritionist.

“Fish is also an excellent source of high quality protein, required for muscle repair and promoting stable energy levels,” she says.

Sushi contains a range of vitamins and minerals

Fish and pickled ginger are good sources of potassium, which controls the balance of fluid in the body and supports heart health. The fish will also provide magnesium (turns food we eat into energy), selenium (supports the immune system) and B vitamins (vital for brain and heart health).

“The seaweed (nori) used to wrap sushi contains key micronutrients like iodine and vitamin C,” as well as vitamin A (strengthens immune health) and E (maintains skin and eye health), says Pearson. Iodine helps the body make thyroid hormones, which keep our cells healthy, while vitamin C maintains healthy skin, blood vessels and bones.

Wasabi may protect against illness

Wasabi is a spicy Japanese root vegetable, similar to horseradish, that is often served as a paste with sushi. Its hot taste is a result of a compound called glucosinolates, which are thought to have anti-inflammatory and anti-cancer properties.

While a high-glucosinolate diet is linked to lower rates of chronic diseases, the level present in a small serving of wasabi alongside sushi won’t have a significant effect, Dr Brewer notes.

Pickled ginger benefits gut health

“Pickled ginger, often served with sushi, is a fermented food, beneficial for gut health,” says Pearson. Eating fermented food has been found to increase the diversity of microbes living in our gut (which has been linked to better overall health) and reduce inflammation.

“Ginger also has known anti-inflammatory and antimicrobial benefits,” she adds.

Can it have a negative effect on your health?

Sushi rice can spike blood sugar. Each 100g serving of sushi rice contains 80g of carbohydrates, which can trigger a spike in blood sugar, explains Brewer. Sugar is also usually added to the rice, along with rice wine vinegar and salt, to make it stickier and sweeter, she adds.

Soy sauce is high in salt

Soy sauce is a staple dip served with sushi but a single tablespoon contains 2.4g of salt. For context, adults are advised to have no more than 6g per day, with less being better. Eating too much salt can cause high blood pressure, which increases the risks of heart attacks and strokes.

Oily fish can contain pollutants

Sushi typically contains oily fish, such as salmon, which tends to have higher levels of pollutants than other types of fish.

These include mercury, polychlorinated biphenyls (PCBs) and heavy metals, Dr Brewer explains. “These can build up in the body,” and, for women, she adds this may also affect the development of a baby in the future.

As a result, girls and women who want to have children at some point are told to limit themselves to two portions per week (280g in total). Pregnant and breastfeeding women may want to avoid eating raw fish completely, Dr Brewer adds.

However, boys, men and women past reproductive age can eat up to four portions of oily fish per week, she notes.

How much should you include in your diet?

“Sushi can be included as part of a healthy, varied diet, but like everything, too much is not good,” explains Brewer. “Guidelines recommend aiming to eat at least two portions of fish a week of which one is oily. A portion is around 140g.”

A serving of sushi, around six to 10 pieces, usually does not contain 140g of fish, however, so sushi fans may be able to have more than two portions per week.

How much salt does sushi contain?

Eight pieces of a spicy tuna roll can provide 2.3g of salt, which is more than a third of the recommended daily intake, Dr Brewer says. This figure increases if you add soy sauce (2.4g per tablespoon), wasabi (0.3g per teaspoon) and pickled ginger (0.2g per tablespoon).

What are the healthiest sushi options?

Sashimi

“Sashimi is a low-carb, high-protein option rich in omega-3 fatty acids,” says Pearson. For example, a portion of salmon sashimi contains just 252 calories and 37g of carbohydrates, while packing in 12g of protein.

Seaweed salad

Seaweed salad is low in calories and high in protein. “Seaweed salad also provides iodine, fibre, and antioxidants, making it a light and nutritious side dish,” says Pearson.

Salmon and avocado rolls

“Salmon and avocado rolls offer a balance of protein from the fish and healthy fats from the avocado, making them a more filling and nutrient dense alternative to more rice-heavy options,” Pearson explains.

What are some of the unhealthiest sushi options?

Tempura rolls

“Tempura rolls contain deep-fried ingredients like tempura prawns or vegetables,” says Pearson. “The frying process means they contain refined seed oils heated to high temperatures which promote inflammation.”

Spicy sushi rolls

“Spicy rolls with mayo contain mayonnaise-based sauces, which are made from refined, inflammatory oils,” Pearson says.

Crispy onion rolls

“Crispy onion rolls are often topped with mayonnaise and fried crispy onions, making them a less healthy choice compared to simpler rolls,” says Pearson.

“These options are better kept for an occasional treat, rather than a daily lunch,” she adds.

Expert verdict: Is sushi healthy?

On the whole, yes. “Sushi can make a healthy, light meal,” says Brewer.

Aim to buy top-quality, freshly made versions, rather than those that have been sitting on a supermarket or sushi bar shelf for most of the day, she recommends.

“Check salt and sugar content where this is listed in ingredients. Avoid adding lots of soy and other sauces to limit your salt intake.”

The Telegraph, London