Everyone loves Japanese food. Especially sushi and sashimi. With an emphasis on raw fish, they are a spring clean on a wooden tray - or conveyor belt - the epitome of fresh, beautiful and healthy.

Or are they?

Blue fin tuna is losing its scaly grasp on existence and while the world is up in fins about the effect our greediness is having, the inimitable auctioneers at Tsukiji market are still lining them up, and shipping them to suppliers and restaurants around the world, where we are still hoovering up bite-sized slices, artfully arranged just so, dipped into soy and wasabi.

Plus, tuna and salmon, being some of the last in the food chain link before humans, are most at risk of gobbling up and passing on heavy metals like mercury. 

So how at risk are we?

Over a bento box lunch at NOBU, I talked with Chef Oyvind Naesheim, originally from Norway. Having sliced and diced his way through Nobu London and Nobu Hong Kong he's about to lead the launch of Nobu Beijing. 

Bento Break

First, though, he created a combination of the restaurant's dishes, with an emphasis on health: seaweed and cucumber salad (fresh, crunchy and with a perfect hint of sharpness via vinaigrette); black cod with brown rice salsa (black cod is one of my favourites and this one was melt-in-the-mouth tasty with a surprisingly western lid of brown rice); soba noodles with baby lobster, egg and sesame sauce (a fun mess of squelchiness and distinctly Asian flavours).

Colourful circles of maki with pickles and shiso leaves (the sweet-acid of the flavour and soft tender seaweed that held it together was pure quality); salmon, yellowtail and mackerel sashimi (I'm still in raptures); and tofu and mushroom miso soup (soul satisfying). I make no apologies for the unequivocally wonderful review - it just was fantastic.

Next up was the Chocolate Bento Box with green tea ice cream and a second pudd of caramelised banana tofu with caramel ice cream and bitter chocolate. The textures, the smells, the flavours were alchemy conjured up by a wizard. Maybe I don't get out enough. Well, sadly that is true - but moving on...

The Issues

Between gurgles of pleasure, sips of tea and occasional glimpses out of the plate glass windows to the slow motion shipping traffic silently floating by, Chef Naesheim talked me through some of raw fish's most burning issues.

"Blue Fin Tuna is a passion of culture," he says, diving into the stickiest issue currently surrounding Japanese cuisine. "We are a Japanese restaurant and Japanese people eat tuna as a source of protein. People demand it, and despite the protests, the government says it's okay to fish it. If it was made illegal we wouldn't use it. We're not promoting it, but it is available and so we let the customer choose."

Passing the to-be-ethical-or-not-to-be question to their guests is one way of dancing around a delicate issue. Of course the argument is far more complex than simply knocking it off a menu, with thousands of jobs, not just in Japan but worldwide, and significant slices of economies dependent on the industry. These facts should not only temper the most stringent tuna-hugger but also motivate governments to pass laws on controlling fishing. Just like everything else in the environmental world, without some TLC right now, there may not be any to care for, or eat, in the future.

Interestingly, Japan wasn't always a sushi-eating country. Way back in the mists of time, food preservation methods travelled around Asia, bringing the idea of salting fish and wrapping it with vinegar rice to the shores of Tokyo, then called Edo. The Japanese, unlike their fellow Thais and Chinese, refused to waste the rice by throwing it away, and by adding less salt they combined the two as a snack that was initially sold off a trolley on the streets of the capital. The vinegar - and wasabi - also killed the bacteria and parasites, handily. In fact, while my yellowtail and salmon sashimi were fresh, the mackerel in my bento box had been lightly treated with vinegar, to make sure all those pesky bacteria weren't going to come back to haunt me. 

Not Worried

Of course Chef Naesheim and his team are rigorous in testing and monitoring the quality of all the food they use. "We test for heavy metals," he adds, "for example mercury, specifically in sashimi." It's another major issue, with salmon and tuna specifically being the last link in the food chain before us, but Chef assured me that to experience significant poisoning you'd have to eat impossible amounts of fish a day. 

With a boss as renowned as Nobu to impress (and of course Robert de Niro), a public who are becoming more and more educated in terms of cuisine, and so many issues surrounding the fishing, preparing and eating of raw fish, Chef Naesheim is understandably a stickler for quality and anticipates finding the best suppliers in China may be his next biggest challenge. "The first thing I did when I came to Hong Kong was go to all the suppliers to meet them. I have to trust them, and don't want to work with anyone I can't rely on 100 percent. We spend time to research where our products come from."