Meat and poultry are excellent sources of protein, B vitamins and certain minerals, but consuming even small amounts of processed meat increases the risk of colorectal cancer.

Processed meats.

“We see a 4 per cent increase in the risk of cancer even at 15g a day, which is a single slice of ham on a sandwich,” said Dr Nigel Brockton, director of research for the American Institute for Cancer Research. Eating a more typical serving of 50g of processed meat a day would increase the risk of colorectal cancer by 18 per cent, a 2011 review of studies found.

Unprocessed red meat, by comparison, increases cancer risk only at amounts greater than 100g a day, and the evidence for that link is limited, Brockton said, adding that the institute advises people to “limit” red meat but “avoid” processed meat.

There is some evidence suggesting an association between processed meat and stomach cancer. And a recent study found an increased risk of breast cancer among women who ate the most processed meats.

Processed meat refers to any meat, including pork, poultry, lamb, goat or others, that has been salted, smoked, cured, fermented or otherwise processed for preservation or to enhance the flavour. The category includes hot dogs, ham, bacon and turkey bacon, corned beef, pepperoni, salami, smoked turkey, bologna and other luncheon and deli meats, sausages, corned beef, biltong or beef jerky, canned meat and meat-based preparations and sauces, among others.

Many of these meats tend to be high in salt and saturated fat, though lean and low-sodium options are available.

Processed meats are often cured by adding sodium nitrite, which gives them a pink color and a distinct taste, or by adding sodium nitrite and lactic acid, which provides a tangy taste, according to The American Meat Institute. In the past, nitrates, in the form of saltpeter, were traditionally used. Nitrates or nitrites inhibit the growth of botulism and scientists suspect they may be involved in the formation of cancer-causing compounds in the body. (Vegetables also contain nitrates and nitrites, but eating them is not associated with an increased risk of cancer.)

Some products that claim to be “natural” or “organic” may say they are processed without nitrites or nitrates, and the label may say the item has “no artificial preservatives” or is “uncured". But nutritionists warn that food manufacturers may still add vegetable powders or juices such as celery juice or beetroot juice that contain naturally occurring nitrates, which are converted to nitrites either in the food itself or when they interact with bacteria in our bodies.

The food label will state that there are “no nitrates or nitrites added", but an asterisk will often lead to a fine-print addendum with the clarification, “except those naturally occurring in celery juice powder", sea salt or a vegetable juice.

As a result some “natural” or “organic” roast beef and turkey breast, or other products cured with sea salt, evaporated cane juice, potato starch, or natural flavorings or seasonings, may end up with just as high a nitrite content as meats with sodium nitrite added.

Adding to the confusion for consumers is that the U.S. Department of Agriculture requires these meats be labeled “uncured” because they are produced without added nitrites or nitrates.

“The average person goes to the store and sees claims like ‘organic', ‘natural' or ‘no added nitrates or nitrites', and they assume those meats are safer, and they’re not,” said Bonnie Liebman, director of nutrition at the Center for Science in the Public Interest, a food safety advocacy group.

The bottom line: If you’re trying to avoid processed meats in order to reduce your risk of cancer, it may be hard to know whether products labeled “natural", “organic", “uncured” or “nitrate and nitrite free” fall into this category or not.

The CSPI has been urging the Department of Agriculture to require labels on processed meats and poultry that identify the products and inform the public that frequent consumption may increase the risk of colon cancer. A spokeswoman for the USDA’s Food Safety and Inspection Service, Veronika Pfaeffle, said recently that the petition, filed in December 2016, is still “under review”.

By Roni Caryn Rabin © The New York Times 2018