Thursday, January 6, 2011

Is eating too many smoked and cured foods bad for me?

Dr Thomas Stuttaford
A 55-year-old reader from Chiswick has written to ask if eating cured foods, especially smoked cured foods, is dangerous. He fears that they may represent an appreciable medical hazard. He especially enjoys eating traditionally wood-smoked bacon, ham, chicken breast and kippers. He always prefers wood smoked products to unsmoked cured meats, but wonders if this is a wise decision.
Our reader shares a similar palate to my own. However, unlike him I am able to enjoy smoked goose breast or Yarmouth bloaters without worrying about the possibility that the cancer-forming (carcinogenic) chemicals found in cured meats or fish represent a significant danger to the ordinary diner.

For rather than being concerned about the curing process, which is well controlled by manufacturers, I am grateful that the salt and sodium nitrite used in the process deal a death blow to any Clostridium botulinum present. This is the bacterium that can cause botulism, a form of food poisoning that can have devastating, even occasionally fatal, results. The curing process also stops the meat going bad.

Most cured meats contain nitrosamines. These are formed when amines — breakdown constituents of proteins — are mixed with the sodium nitrite that, with salt (sodium chloride), is used to cure and preserve meat. The combination of small quantities of salt and sodium nitrite is such an effective mixture in preventing food poisoning and preserving the meat that no comparable alternative has been found.

Although there is evidence that nitrosamines are carcinogenic, it is doubtful if, in the small amounts the average person takes, it increases appreciably the risk of developing cancer after exposure to cured ham, bacon, other meats and fish. Choosing smoked meats and fish as an occasional hors d’oeuvre, or even having them as a main course from time to time, is unlikely to be significant. Research suggests that most people derive far more nitrates from vegetables, including such old faithfuls as spinach and cabbages, than from cured meats. It is estimated that only 1 per cent of someone’s nitrite concentration in the gut has been derived from cured meats and 90 per cent from vegetables. Nitrates are reduced to nitrites by organisms in the intestinal tract. Even so, it wouldn’t be considered a good idea to dine exclusively on cured and smoked foods.

Anxious lovers of smoked foods may also worry about the effect of benzopyrenes — potentially potent carcinogens — produced by smoking food. In smoked foods the levels of these may exceed 50 micrograms per kilogram. The relevant factor in considering possible problems caused either by the curing with salt and sodium nitrite or by the benzopyrenes from smoking is the amount of exposure to them. People who have a mixed diet can occasionally relish smoked foods without fearing that a few mouthfuls of smoked eel need to be followed by an immediate call to their local solicitor to update their will.

Those people who are obsessed with possible carcinogens in their food may also worry about the standard rasher or two of bacon in what hotels call the traditional English breakfast. They should perhaps choose to send back any burnt toast. Burnt toast, too, has a theoretical carcinogenic potential. Likewise, so has any unsaturated fat cooked at a high temperature. Research on cooking bacon has shown that the microwave is safer than the frying pan. The level of the nitrosopyrrolidines, a toxic substance produced by heating nitrosamines, is virtually undetectable when the bacon is cooked at a low temperature very slowly.

The crispier the bacon the higher the content of nitrosopyrrolidines. A medium well-done rasher cooked at 210F (99C) has ten times the quantity of nitrosopyrrolidines asmin slowly heated bacon. Cooked at 400F quickly, it has 17 times the amount and in crisped (virtually burnt) bacon there are 19 times as much nitrosopyrrolidines.

The good news is that the evidence that crispy bacon has ever harmed anyone is lacking. In fact there are more carcinogens in very hot fat. Another piece of reassuring news is that vitamin C in breakfast fruit juices may help to counteract nitrosamines.