It used to be a food reserved for special occasions such as Christmas. But smoked salmon has become such a common part of our diet nowadays that it’s even available in sandwiches on the petrol station forecourt.
But experts are warning that consuming too many of the chemicals created during the food smoking process could increase the risk of certain types of cancer.
And it’s not only smoked salmon – smoked meats and cheeses, even smoky bacon crisps can also contain carcinogenic (cancer-causing) chemicals.
Smoking food involves hanging it above smouldering wood. When the wood burns under low-oxygen conditions during the smoking process, this produces chemical compounds that settle on the food.
This includes polycyclic aromatic hydrocarbons (PAH), known to be carcinogenic.
‘These compounds can be harmful to the body when ingested at high concentrations,’ explains Dr Idolo Ifie, a lecturer in food processing and food chemistry at the University of Leeds.
‘Avoiding them completely would be extreme, but people should be more conscious of the amount of smoked foods they eat – and aware of the potential danger.’
Studies have linked the consumption of foods with high levels of PAHs to an increased risk of developing cancer, such as breast, prostate and colorectal cancer, he adds.
Experts warn that consuming the chemicals created during the food smoking process could increase the risk of certain types of cancer – including for smoked salmon
At one point, it was hoped smoke flavourings – used in crisps such as smoky bacon flavour – might prove a better alternative to traditional smoking methods
While the presence of carcinogenic compounds such as PAHs in smoke has been known about for decades, recent scientific studies have highlighted that the levels in commonly consumed smoked foods are higher than expected, leading to a greater urgency in classifying them as health risks, explains Dr Ifie.
For example, a study published in the scientific journal Discover Food in 2024 found that samples of smoked meat and fish had higher concentrations of PAHs than the same types of meat and fish which had been grilled.
The scientists concluded that the levels of PAHs in the smoked foods were higher than EU recommendations, and that some of the smoked fish tested (including mackerel) appeared to have the highest levels.
Traditionally, smoking food was used for preservation, but now it’s used more widely to add flavour, says Jane Parker, a professor of flavour chemistry at the University of Reading.
And smoking food simply for flavour is often done at higher temperatures, as this creates a stronger taste, adds Dr Ifie – but this also creates more harmful compounds.
While experts want to increase awareness of the harms of smoked food, a problem for consumers is it’s difficult to know how much you’re likely to be ingesting – or what is a safe level of, say, smoked salmon to eat.
Smoking food was used for preservation, but now it’s used more widely to add flavour, says Jane Parker, a professor of flavour chemistry at the University of Reading
This is because there are many different factors that affect the amount of PAHs that end up on the food, says Dr Ifie.
These include the temperature of the smoke (high temperatures lead to higher levels of the compounds), the length of smoking time, how far away from the smoke the food is positioned and the type of wood used.
Research carried out at the University of Bucharest in Romania found that plum, alder and birch wood produced the highest amount of PAHs, while applewood created the least during the smoking process, reported the Journal of Agricultural and Food Chemistry in 2020.
Currently there are no regulations in the UK on what type of wood can or can’t be used. Oak is the most commonly used in UK food products, says Dr Ifie.
One option for consumers trying to protect themselves from the potential health risks of smoked foods might be to look for milder strength versions of foods (for instance with smoked salmon you can see ‘mild’ or a strength rating out of five on the label which indicates this) which means that less heat has been used in the smoking process and they are likely to contain a lower amount of PAHs.
And smoked meat may be worse than smoked salmon – because fattier foods create more of these compounds during the smoking process.
‘The higher the fat content of the food, the higher the amount of PAHs, because dripping fat creates more smoke, and then those smoke particles also stay on the food – so fatty meats are likely to contain more of these compounds than fish, for example,’ explains Dr Ifie.
At one point, it was hoped smoke flavourings – used in crisps such as smoky bacon flavour, soups and sauces as well as in meat, cheese and fish – might prove a better alternative to traditional smoking methods. However, these are not risk-free.
‘EU legislation has done a complete 180-degree turnaround and announced in 2024 that it would be banning smoke flavourings,’ says Professor Parker.
This is because these contain the same harmful chemicals produced by wood smoking, as they’re usually made synthetically or by condensing real smoke, say experts.
‘Whether you use smoke flavourings or the traditional smoking method, you will be exposed to carcinogens,’ says Professor Parker.
‘Smoke flavourings incorporate liquid smoke – it can be purified to a certain extent, but it still has a component of smoke in it so you can’t remove the carcinogens entirely.’
The good news is that most of us carry specific enzymes that break down PAHs effectively so that they leave our body as waste (how many this affects is not known).
As Dr Ifie explains: ‘It’s thought that whether or not you can metabolise these compounds comes down to genetics and differences between our immune systems – for example, those with a suppressed immune system [such as people taking immunosuppressant drugs for conditions including rheumatoid arthritis or psoriasis] may be more susceptible to these harmful particles, but there is no way to know if you have the enzyme or not.’
The simple rule is to eat smoked foods ‘in moderation’, says Dr Ifie, who limits smoked foods – mainly fish – to once a week.
‘And bear in mind, consuming it all the time could create a build-up of harmful compounds in the body over time.’
It’s all about the dose, agrees Professor Parker. She eats smoked salmon once or twice a week – as it’s her source of omega 3s, which are good for brain health and protect against heart disease – and has smoked bacon about once a month and eats smoked cheese a few times a year. She also cooks with smoked paprika regularly.
Professor Parker eats smoked salmon once or twice a week – as it’s her source of omega 3s, which are good for brain health and protect against heart disease
‘We’re facing this challenge with food in that many foods we consume have low levels of things that are pretty harmful, but there are also health benefits to eating them,’ she adds.
For context, she points out that dietary survey data shows that average daily intake of Benzo(a)pyrene – a main type of PAH, known to be particularly toxic – for an adult is four to six nanograms per kilogram of body weight, which can come from food as well as pollution and other sources, she explains.
‘If this amount was to come purely from smoked salmon, a 70kg (or 11st) adult would have to eat 5kg (or 11lb) of smoked salmon per day,’ she says.
‘So even eating a whole 100g pack of traditionally smoked salmon every day would have negligible impact on our average dietary intake, and negligible increase in cancer risk.’
But, of course, smoked salmon may not be the only smoked food in your diet.
‘Smoked foods shouldn’t form a large part of your diet, but I wouldn’t be concerned about eating them in small quantities around once a week,’ advises Clare Thornton-Wood, a dietitian based in Sussex and a spokesperson for the British Dietetic Association. She points out that they also tend to be high in salt, which is bad news for blood pressure, and in turn, raises the risk of heart attack and stroke.
That said, smoked salmon – like other oily fish, such as mackerel and sardines – can be a valuable source of omega-3s, she adds, ‘and we know that, in general, people aren’t eating enough omega-3s’.
‘Ideally it would be better to eat fish that isn’t smoked – for example grilled, poached or tinned fish.
‘Similarly, cheese is high in protein and calcium – so I wouldn’t want to stop people eating cheese, but it would be sensible to limit how much smoked cheese you have.
‘I think it’s useful to think about what’s in your food, so if you’re eating a lot of smoked products it’s worth considering cutting down – but you don’t need to stop eating them entirely.’
