OK OK, so maybe the title of this post is a little misleading. Of course the benefits of eating oily fish outweigh the potential for negative impact as it is an excellent source of vitamin A and D as well as omega 3, an unsaturated fatty acid with many ‘potential’ health benefits. However I want to focus on a specific type of fish in specific cuisine that has a significant risk associated with it.
Chinese-style salted fish is a food which has been regularly consumed in Southeast Asia for many years. The method of preparation is to catch said fish, leave to soften (partially decompose) and then preserve with salt and eat at a later date. However what this food stuff is rich in is N-nitrosodimethylamine (NDMA.) NDMA is an extremely toxic chemical that is known to be carcinogenic to humans in even the smallest of doses. This odourless, colourless chemical was originally used to produce rocket fuel in the 1970’s and is now a chemical for inducing cancer in rats in the laboratory. Someone even spiked someone’s drink with NDMA and ended up murdering both the person they intended and an 11 month old child. The electric chair was their punishment.
Although I’ve said NDMA is highly toxic it is also a common volatile amine. Naturally it is found in malt vinegar, cheese, beer, whisky, tobacco, and cured meats and fish and in high enough doses can result in severe hepatic toxicity – fibrosis (scarring) and liver failure can result. However NDMA doesn’t accumulate in the body and as such there shouldn’t be fear over going on a cheese binge. Having said that drinking and smoking does have a few associated risk factors...
What is interesting in all this is epidemiological studies have shown that the incidence of nasopharyngeal carcinoma (NPC for short, a cancer of the bit between your nasal passage and the back of your throat) is significantly high in regions where salted fish is part of the diet. And the studies suggest that it is the consumption of salted fish and NDMA that is the cause of the significant cancer levels in China. This research has not stopped there as there are obviously other regions in which salted fish is regularly consumed, namely in North Africa and Alaska. Again, the studies conducted here show a significant level of NPC in those who consume salted fish. I think we see the pattern...
This research isn’t new however – this news story (well I don’t ever remember seeing this on the news) was first published in 1982... almost thirty years ago. It was only through a colleague of mine at medical school that I learnt about running the risks of eating Chinese food. Before I always thought all I had to worry about was a dodgy curry.
